Water electrolysis has been considered as one of the most effective, secure and sustainable ways to produce clean hydrogen energy to resolve the looming energy and environmental crisis. Exploring bifunctional catalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with high efficiency, low cost, and easy integration is crucial for future renewable energy systems. Herein, we report the in situ controllable synthesis of hierarchical MoP/Ni2P heterostructures on 3D Ni foam (MoP/Ni2P/NF) and their application as an efficient bifunctional electrocatalyst for water splitting. The hierarchical heterostructures are achieved by a facile hydrothermal approach to obtain the Mo-based/NF precursor, followed by a subsequent in situ phosphorization procedure. Through manipulating the concentration of ammonium molybdate for the preparation of the precursor as well as the phosphorization temperature, the optimal MoP/Ni2P/NF can be achieved which can efficiently catalyze both the OER and HER in alkaline electrolytes. The superior performance with robust durability is mainly attributed to unique hierarchical heterostructures and collaborative advantages of bimetallic phosphides, as well as the 3D porous conductive substrate. As an integrated high-performance non-noble electrocatalyst for overall water splitting, the MoP/Ni2P/NF electrode requires a cell voltage of only 1.55 V to achieve a current density of 10 mA cm−2 in alkaline solution. This work highlights the importance of the design and construction of hierarchical heterostructures for efficient overall water splitting.

In our efforts to obtain Pt-free oxygen reduction reaction (ORR) electrocatalysts with high efficiency for fuel cell and metal–air battery, design, and preparation of novel materials with desired morphology and active sites are vitally necessary. Herein, a novel MoC-based ORR catalyst with high efficiency is achieved. The proposed catalyst is comprised of ultrasmall-sized MoC nanoparticles (average size ∼ 1.5 nm) entrapped into 3D porous frameworks of N-rich graphene (NGr), which is synthesized by using layered C3N4 as a sacrificial template via a facile pyrolytic approach. Possessing unique structural features (including preferential O2 absorbing sites, good accessibility, favorable conductive and protective 3D frameworks of NGr), the MoC/NGr catalyst exhibits positive onset- and peak- potential at 0.93 and 0.80 V for ORR in alkaline media with good four-electron selectivity (n ≈ 4.0), which is promising and even competitive to commercial Pt/C, particularly in terms of cost-effectiveness, the ease of preparation, significantly improved methanol tolerance, and enhanced stability. Other prospective application of MoC/NGr could also be broadened to biomimic catalysis, energy conversion, storage devices, and so on.

Controllable engineering of high-electronegativity oxygen (O)-heteroatoms into MoS2 ultrathin nanosheets is realized via a facile post-modification process. The incorporated oxygen atoms impart a dramatically enhanced ORR activity to the pristine nanosheets, with a 7.8-fold current increase as well as 180 mV and 160 mV positive shifts in both onset and half-wave potentials that are almost comparable with the commercial Pt/C catalyst. Furthermore, oxygen incorporation also triggers a transformation of the process from two-electron to a four-electron process. The improved topical conductivity, as well as the preferential adsorption of oxygen molecules originating from the heteroatoms engineering is supposed to be responsible for the efficient ORR. The prospect of controllably engineering heteroatoms into MoS2 ultrathin nanosheets with versatile applications is also highlighted in this work.

MoS2 nanodots (NDs) were successfully embedded in the three-dimensional (3D) porous frameworks of N-doped graphene (NGr) via in situ pyrolysis of glucose, a layered C3N4 sacrificial template and monolayered MoS2 NDs. The monolayered MoS2 NDs were hydrothermally pre-synthesized and acted as size-controlled precursors. By varying the content of the MoS2 NDs, a series of MoS2 NDs/NGr was obtained, which displayed amendable activity towards oxygen reduction reaction (ORR) in basic solution, due to the balance between the exposed edge sites of the MoS2 NDs and the internal conductive channels of the 3D porous NGr. The optimal composition generated an efficient Pt-free ORR catalyst with good four-electron selectivity, and was shown to have a more positive shift in both the onset and peak potentials than its counterparts. The novel catalyst also demonstrated superior tolerance against methanol and better durability than commercial Pt/C.

Uniform iron carbide nanoparticles (Fe3C, ∼10 nm), size evolved from nano-scaled Fe-MIL-88b, were one-pot pyrolytically embedded in 3D porous N-rich graphene. Extra ORR catalytic activity with four-electron selectivity was achieved in an alkaline electrolyte. The onset and peak potential were 10 mV and 40 mV more positive, respectively, than commercial Pt/C.

Engineering phosphorus heteroatoms into the plane of ultrathin MoS2 nanosheets is realized via a facile thermolytical process. The doping of low-electronegative P atoms generates an extra ORR activity with four-electron selectivity, manifesting seven-fold current increase as well as 160 mV positive shift in both onset and half-wave potentials.

•Soft templated mesoporous carbon nanosphere (MCNS) as an active electrode material.•Good accessibility of MCNS was exemplified by simultaneous detection of biomolecules.•Conductive nonporous carbon and inert mesoporous silica nanospheres were designed too.•A comparative study on three nanospheres was performed for intrinsic activity of MCNS.•Both pores and carbon skeleton with defects are beneficial to the activity of MCNS.Mesoporous carbon electrode materials have attracted attention in analytical chemistry and materials science, particularly in the electrochemical determination of biomolecules, because of their open-pore structure, large surface area, and high electrochemical activity. In this study, novel mesoporous carbon nanospheres (MCNSs) with open-pore structure, which is beneficial in preparing dispersible phases of powders for sensor fabrication, were designed and synthesized using a facile soft template approach. The accessibility of the MCNS-based active electrode material was demonstrated by simultaneous determination of dopamine, ascorbic acid, and uric acid at physiological pH. The dispersibility of MCNS was manifested by the improved stability and reproducibility of the fabricated electrochemical sensor. Meanwhile, another two similar nanospheres, namely, carbon nanospheres without open-pore structure and electrochemically inert mesoporous silica nanospheres, were also fabricated to determine the origin of the catalytic activity of the MCNSs. The high activity of the MCNS-based electrode materials can be attributed to their nanoporous structure and conductive carbon skeleton that contains high degree of defects. In addition, highly open nanopores allowed easy access of the targets to the defective sites on the nanopore walls, thereby enhancing catalytic activity and reducing response time.

As one of promising catalysts that contain high density of active sites, N doped carbons have been extensively researched, while the reports for N, S dual-doped carbon materials are far less exhaustive. Herein, devoid of activation process and template, N, S dual-doped porous carbon (N–S–PC) was prepared for the first time via one-step pyrolysis of sodium citrate and cysteine. Possessing unique porous structure and large pore volume as well as good accessibility, N–S–PC demonstrates significantly improved electrocatalytic activity toward oxidation of ascorbic acid (AA), dopamine (DA), and uric acid (UA). In the coexisting system, the peak potential separation between AA and DA is up to 251 mV, which is much larger than for most of the other carbons. On the basis of large potential separation and high current response, selective and sensitive simultaneous determination of AA, DA, and UA was successfully accomplished by differential pulse voltammetry, displaying a linear response from 50 to 2000 μM, from 0.1 to 50 μM, and from 0.1 to 50 μM with a detection limit (S/N = 3) of 0.78, 0.02, and 0.06 μM. This work highlights the importance of N, S dual doping and hierarchical porous carbons for efficient catalysis.Keywords: electrocatalysis; N, S dual-doping; one-step pyrolysis; porous carbon

•Seed-growth of highly-dispersed catalytic Pt nanodot on Au nanorod (PtND@AuNR).•Good accessibility of catalytic sites was evidenced by its peroxidase-like activity.•Excellent assay performances of H2O2 at PtND@AuNR-based sensor.Some nanostructures are reported to possess enzyme-mimetic activities similar to those of natural enzymes. Herein, highly-dispersed Pt nanodots on Au nanorods (HD- PtNDs@AuNRs) with mimetic peroxidase activity were designed as an active electrode modifier for fabrication of a hydrogen peroxide (H2O2) electrochemical sensor. The HD-PtNDs@AuNRs were synthesized by a seed-mediated growth approach and confirmed by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and UV–vis spectroscopy. The electrochemical and catalytical performances of HD-PtNDs@AuNRs towards H2O2 reduction were investigated in detail by cyclic voltammetry and amperometry. The HD-PtNDs@AuNRs modified electrode displayed a high catalytic activity to H2O2 at −0.10 V (versus SCE), a rapid response within 5 s, a wide linear range of 2.0–3800.0 μM, a detection limit of 1.2 μM (S/N = 3), and a high sensitivity of 181 μA mM−1 cm−2. These results suggested a promising potential of fabricating H2O2 electrochemical sensor using HD- PtNDs@AuNRs.

•Hemi-ordered nanoporous carbon as an active electrode material•Good discriminating ability towards NO2− from physiological or environmental system•Highly selective determination of nitrite with fast and sensitive current responseHemi-ordered nanoporous carbon (HONC) was obtained from a mesoporous silica template through a nano-replication method using furfuryl alcohol as the carbon source. The structure and morphology of HONC were characterized and analyzed in detail by X-ray diffraction, N2-sorption, Raman spectroscopy and transmission electron microscopy. HONC was then demonstrated as active electrode material for selective determination of nitrite in either physiological or environmental system. Well separated oxidation peaks of ascorbic acid, dopamine, uric acid and nitrite were observed in physiological system, and simultaneous discrimination of catechol, hydroquinone, resorcinol and nitrite in environmental system was also accomplished. Distinctly improved performances for selective determination of nitrite (such as significantly fast and sensitive current response with especially high selectivity) coexisted with ascorbic acid, dopamine and uric acid in the physiological system, as well as with catechol, hydroquinone and resorcinol in the environmental system were achieved at HONC electrode material. The excellent discriminating ability and high selectivity for NO2− determination were ascribed to the good electronic conductivity, unique hemi-ordered porous structure, large surface area and large number of edge plane defect sites contained on the surface of nanopore walls of HONC. Results in this work demonstrated that HONC is one of the promising catalytic electrode materials for nitrite sensor fabrication.

Ultrafine CuO nanoparticles (UCNs) were well-isolated in the nano-channels of ordered mesoporous carbon (OMC) via a double solvent procedure. In this approach, uniform OMC meso-channels of large surface area acted as nanoreactors embedded with small nanoparticles. n-Hexane was used as hydrophobic solvent to disperse OMC, and hydrophilic Cu(NO3)2 aqueous solution served as a precursor to fill the nano-channels. The interfacial force between double solvents of Cu(NO3)2 and n-hexane facilitated the precursor filling within the OMC mesopores, and the subsequent heat treatment triggered in situ isolation of UCNs within OMC porous channels. This final product was denoted as UCNs@OMC, and the structure and morphology of UCNs@OMC were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2-sorption. Increased glucose oxidation currents implied the accessibility of the active catalytic sites of UCNs@OMC, and an UCNs@OMC based glucose sensor was fabricated and tested exhibiting good reproducibility and selectivity.

•OMC with large surface area and open pore as active electrode material.•Highly selective determination of Tyr in the presence of CysH at physiological pH.•Wide linear range for Tyr from 15 to 900 μM.In this study, a novel ordered mesoporous carbon (OMC) with high surface area (1600 m2/g), large pore volume (1.6 cm3/g) and open pore structure was successfully prepared by using a hard-templated method. This porous carbon material provided an amplified target-receptor interface for the electrochemical application. As a novel electrode material, the catalytic activities of OMC towards simultaneous electro-oxidation of tyrosine (Tyr) and l-cysteine (CysH) were investigated by differential pulse voltammetry. Significantly, well separated oxidation peaks of Tyr and CysH were firstly observed at physiological pH at the OMC electrode. Selective determination of Tyr was carried out in the presence of CysH. More importantly, well distinguishing Tyr from ascorbic acid, dopamine, uric acid, epinephrine was also demonstrated, suggesting an excellent anti-interference ability of this Tyr sensor in the physiological system.

•Tunable free radical polymerization of ionic liquid on MWCNT surfaces.•Discrimination of hydroquinone and catechol at functional electrochemical interface.•Excellent performances in simultaneous determination based on cation-π interaction.Tunable polymerization of ionic liquid on the surfaces of multi-walled carbon nanotubes (MWCNTs) was achieved by a mild thermal-initiation-free radical reaction of 3-ethy-1-vinylimidazolium tetrafluoroborate in the presence of MWCNTs. Successful modification of polymeric ionic liquid (PIL) on MWCNTs surfaces (PIL-MWCNTs) was demonstrated by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy. The resulting PIL-MWCNTs possessed unique features of high dispersity in aqueous solution and tunable thickness of PIL layer, due to positive imidazole groups along PIL chains and controllable ionic liquid polymerization by tuning the ratio of precursor. Based on cation-π interaction between the positive imidazole groups on PIL-MWCNTs surface and hydroquinone (HQ) or catechol (CC), excellent discrimination ability toward HQ and CC and improved simultaneous detection performance were achieved. The linear range for HQ and CC were 1.0 × 10−6 to 5.0 × 10−4 M and 1.0 × 10−6 to 4.0 × 10−4 M, respectively. The detection limit for HQ was 4.0 × 10−7 M and for CC 1.7 × 10−7 M (S/N = 3), correspondingly.

Nanoporous carbon materials have attracted significant interests in the design of electrodes for electrocatalysis and biosensors. Here, three templated nanoporous carbons (TNCs) materials with substantial different specific surface area were designed and synthesized by a nanocasting method, in which mesoporous silicates and acid were used as template and catalyst, respectively. The TNCs were then used as electrode materials for simultaneous detection of dopamine (DA), ascorbic acid (AA) and uric acid (UA) at physiological pH. The correlations between specific surface area, edge-plane defect sites in TNCs and their distinguishing ability towards AA, DA, and UA were investigated. For TNCs with substantial larger specific surface area and more defect sites, the oxidation peaks of AA, DA and UA were separated well and their oxidation currents increased remarkably. A highly sensitive electrochemical sensor for simultaneous detection of those biomolecules was achieved by designing TNCs1 with the largest specific surface area and the most defect sites as the electrode material. The sensitivity of AA, DA and UA at the sensor is 0.012, 4.031, 0.605 μA/μM respectively. Results suggest that TNCs1 is promising in biomolecules simultaneous detection. This work may also be valuable for scientists who search for excellent carbon materials for biosensing and electrocatalysis.Highlights► TNCs materials with different specific surface area and defect sites were designed. ► Catalytic activities of the TNCs were correlated with the amount of defect sites. ► TNCs with more defects indicate a satisfied property in oxidation of AA, DA and UA. ► A sensitive sensor without interference in detection of AA, DA and UA was proposed.

The electrochemical fructose sensor attracts considerable attention in the food industry and for clinical applications. Here, a novel fructose biosensor was developed based on immobilization of highly dispersed CuOCu nanocomposites on Graphene that was non-covalently functionalized by sodium dodecyl benzene sulfonate (SDBS) (denoted briefly as SDBS/GR/CuOCu). The structure and morphology of SDBS/GR/CuOCu were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemistry and electrocatalysis were evaluated by cyclic voltammetry (CV). The fructose sensing performances were evaluated by chronoamperometry (i–t). Those properties were also compared with that of CuOCu. Results revealed the distinctly enhanced sensing properties of SDBS/GR/CuOCu towards fructose, showing significantly lowered overpotential of +0.40 V, ultrafast (<1 s) and ultra-sensitive current response (932 μAm M−1 cm−2) in a wide linear range of 3–1000 μM, with satisfactory reproducibility and stability. Those could be ascribed to the good electrical conductivity, large specific surface area, high dispersing ability and chemical stability of GR upon being functionalized non-covalently by SDBS, as well as the outstanding cation anchoring ability of SDBS on GR to resist aggregation among Cu-based nanoparticles during electro-reduction. More importantly, an improved selectivity in fructose detection was achieved. SDBS/GR/CuOCu is one of the promising electrode materials for electrochemical detection of fructose.Highlights► Highly stable GR dispersion was achieved by SDBS non-covalent functionalization. ► High charge density of SDBS/GR confined growth of CuOCu nanocatalysts. ► SDBS/GR/CuOCu displayed ultrafast and sensitive current response toward fructose.

We report on a sensor for epinephrine (EP) that is based on an ITO electrode modified with multi-walled carbon nanotubes pre-coated with a polymerized ionic liquid (PIL-MWNTs). A chitosan film was then electrodeposited on the ITO electrode in the presence of EP (the template) and the PIL-MWNTs. This film acts as an excellent recognition matrix due to its excellent film-forming ability and the many functional groups that favor hydrogen bond formation with the target (EP). The PIL-MWNTs, in turn, can improve the sensing performance due to their good electrical conductivity, high dispersity, and large surface area. The imprinted films were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform IR spectroscopy, and thermogravimetric analysis. The electrochemistry of the imprinted electrode was investigated by cyclic voltammetry, electrochemical impedance spectroscopy, differential pulse voltammetry and chronoamperometry. The response to EP is linear in the 0.2 μM to 0.67 mM concentration range, and the detection limit is as low as 60 nM (at an S/N of 3). The electrode is reusable and offers good reproducibility and stability.

We described the preparation of copper oxide composite nanofibers doped with carbon nanotubes (CuO/C-NFs) or nickel oxide(CuO/NiO-NFs) by electrospinning for direct glucose determination. The interest in exploring practical CuO/C-NFs and CuO/NiO-NFs electrode materials for sensor application was fascinated by the possibility of promoting electron transfer for kinetically unfavorable glucose oxidation reactions at a lower overpotential and thus improving the selectivity of the electrode for glucose in electroanalysis. The morphologies of CuO/C-NFs and CuO/NiO-NFs were characterized by scanning electron microscopy(SEM) and X-ray powder diffraction(XRD). The electrocatalytic performances of glucose were evaluated in detail by cyclic voltammetry(CV) and chronoamperometry. Facile charge transport, enhanced current response(at a lower overpotential of +0.35 V), improved stability and selectivity, as well as excellent resistance towards electrode fouling were observed at CuO/C-NFs electrode in direct glucose electroanalysis. These merits are attributed to the highly porous three-dimensional network film structure of CuO/C-NFs electrode materials and the potential synergic catalytic effect of CuO and carbon nanotubes in composite nanofibers. This study may provide a new insight into metal oxide-based composite nanofibers obtained via electrospinning for fabricating novel and high performance sensors and devices.

Cobalt oxide-doped copper oxide composite nanofibers (CCNFs) were successfully achieved via electrospinning followed by thermal treatment processes and then exploited as active electrode material for direct enzyme-free fructose detection. The morphology and the structure of as-prepared samples were investigated by X-ray diffraction spectrum (XRD) and scanning electron microscopy (SEM). The electrocatalytic activity of CCNFs films towards fructose oxidation and sensing performances were evaluated by conventional electrochemical techniques. Cyclic voltammetry (CV) and chronoamperometry (I−t) revealed the distinctly enhanced sensing properties towards fructose compared to pure copper oxide nanofibers (CNFs), i.e., showing significantly lowered overpotential of 0.30 V, ultrafast (1 s) and ultrasensitive (18.988 μA mM−1) current response in a wide linear range of 1.0 × 10−5 M to 6.0 × 10−3 M with satisfied reproducibility and stability, which could be ascribed to the synergic catalytic effect of the binary CuO/Co3O4 composite nanofibers and the highly porous three-dimensional network films structure of the CCNFs. In addition, a good selectivity for fructose detection was achieved. Results in this work demonstrated that CCNFs is one of the promising catalytic electrode materials for enzymeless fructose sensor fabrication.Highlights► Binary CuO/Co3O4 nanofiber as active electrode material. ► Dramatically enhanced catalytic activity and direct fructose detection. ► Significantly lowered overpotential, ultrafast (1 s) and sensitive (18.988 μA mM−1) response.

We describe the preparation and sensing capabilities of a bimetallic electrode consisting of copper atoms deposited on gold nanoparticles (GNPs). The electrode was obtained by first constructing a GNP template on the surface of a glassy carbon electrode by exploiting the hydrogen-bonding interactions between pyridine groups on the surface of the GNPs and the carboxy groups of poly(acrylic acid). GNPs (60 nm in diameter) were homogeneously and densely deposited in the template (as revealed by scanning electron microscopy). The electro-deposition of copper ad-atoms on GNPs occurred at an underpotential and was proven by electrochemical techniques. The presence of GNPs in the template accelerated the deposition at low potential due to its beneficial effect on the rate of electron transfer. The new electrode was studied for its response to glucose. Highly stable and reproducible catalytic activity towards glucose oxidation is observed and attributed to the synergistic catalytic effect of the copper atoms on the surface of the GNPs. The detection limit is as low as 50 nM (at a signal-to-noise ratio of 3), and the response is between 200 nM and 10 mM of glucose.

Gold nanoparticles functionalized with self-assembled films of ferrocenylhexanethiol and mercaptoundecanoic acid (MUA) were used for the determination of ascorbic acid (AA). The modified nanoparticles (mNPs) were prepared by a combination of the modified Schifrin’s and the place-exchange methods. Well-organized films were obtained due to electrostatic attraction between the carboxy groups of MUA and cationic surface of poly(diallyldimethylammonium chloride). The mNP films are highly stable and can be exploited to fabricate an enzyme-less sensor for AA whose function is based on the highly electrocatalytic activity of ferrocene in the mNPs towards AA. The sensor was characterized by cyclic voltammetry and chronoamperometry. Under optimal conditions, the response current towards AA is proportional to its concentration in the range from 8.0 μM to 6.0 mM, with a detection limit of 0.14 μM (at a signal-to-noise ratio of 3). This work represents a simple controlled test-bed for fundamental studies on the use of self-assembled mNPs for sensor applications.

This work demonstrates the use of self-assembled carbon films in designing fuel cell electrode. Well-dispersed mesoporous carbon particles were prepared based on the spontaneous and strong chemisorption of polyoxometalate (POM) solution on carbon surface. Electrostatically self-assembled films of the POM stabilized carbon interlaced with cationic polyelectrolyte binding layer were useful for confining electrodeposition of platinum (Pt) catalyst. The structure and morphology of the resulting films were characterized by X-ray diffraction and scanning electron microscopy respectively. The electrocatalytic activities of Pt deposited on the self-assembled carbon films toward the degradation of small organic molecules are largely dependent on the quantity of Pt and carbon. This work represents a simply controlled test-bed for fundamental studies on loading metal catalysts on ordered mesoporous carbon films for catalysis.

The electrochemical properties of electrodes modified with metal/metal oxides depend not only on the nature of the materials but also on the composition and substrate as well. In this study, dendritic CuNi nanostructured materials with a distinguishable bimetal phase were achieved by electrodeposition in 0.05 M Na2SO4 solution containing 0.05 M CuSO4 and 0.05 M NiCl2 at −1.0 V on the surface of titanate thin films, which were self-assembled from the titanate nanaosheets exfoliated by n-propylamine. The structures, morphologies, and elemental molar ratio of the titanate-supported CuNi were analyzed by XRD, SEM, and ICP-AES, respectively. The electrochemical activities of the CuNi nanostructured electrodes toward glucose oxidation were evaluated, and factors that affect the electrocatalytic activities of the electrodes were examined and optimized. The potential applications of the CuNi nanostructured films for fabrication of enzymeless glucose sensors were also investigated. The assay performances of the sensor evaluated by conventional electrochemical techniques revealed a quick response, good reproducibility, and enhanced sensitivity in glucose determination compared with that of pure Cu or Ni electrodeposited on the self-assembled titanate template.

This work demonstrated for the first time the feasibility of electrochemical preparation of copper-based/titanate intercalation electrode material. Cupric ion was first intercalated into the layered titanate host by ion exchange and subsequently reduced by electrochemical methods, resulting in the copper-based/titanate intercalation electrode materials. The successful formation of copper-based/titanate (Cu−TO) intercalation materials by electrochemical reduction following ion exchange (Cu(II)−TO) were characterized by X-ray diffraction, scanning electron microscopy, and conventional electrochemical techniques. The effects of experimental conditions, i.e., dispersant for ion exchange, electroreductive medium, and methods, on activities of the resulting electrode materials toward glucose electrooxidition were investigated in detail. Results revealed that both the stability and the electrooxidative activity to glucose of Cu−TO intercalation electrode materials were largely improved compared with that of Cu(II)−TO, indicating the necessity and superiority of the electrochemical reduction step carried out following ion exchange. The potential applications of this new class of copper-based/titanate materials in electrocatalysis and electroanalysis were demonstrated. Present study provides a low cost and simply controlled test-bed for fundamental study on electrochemical preparation of a new class of metallic/metal-based titanate intercalation materials for electrocatalysis, electroanalysis, and relevant fields.

Copper oxide nanofibers (CuO-NFs) prepared by electrospinning and subsequent thermal treatment processes were demonstrated for the first time for glucose non-enzymatic determination. The structures and morphologies of CuO-NFs were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction spectrum (XRD). Different dispersants were utilized for the suspension preparation and effects of ultrasonic time on the films electrode fabrication were investigated in detail. The assay performances to glucose were evaluated by cyclic voltammetry (CV) and chronoamperometry (I–t). Results revealed a high sensitivity (431.3 μAm M−1 cm−2), fast response (about 1 s), long-term stability and excellent resistance towards electrode fouling in the glucose determination at +0.40 V. The improved performances of CuO-NFs films electrode for electro-oxidation glucose were ascribed to the high surface-to-volume ratio, complex pore structure, extremely long length of the as-prepared CuO-NFs, and the excellent three-dimensional network structure after immobilization. Results in this study suggest that electrospun CuO-NFs is a promising 1-D nanomaterial for further design and microfabrication of bioelectrochemical nanodevices for glucose determination.

Copper-based titanate intercalation electrode materials (referred as Cu–TO) were achieved by electrochemical reduction of the intercalated cupric ions that were ion exchanged on the layer structured titanate films by using n-propylamine as an exfoliating agent. The copper-based titanate intercalation electrode materials were characterized by X-ray diffraction (XRD), electrochemical techniques and inductive coupled plasma-atomic emission spectroscopy (ICP-AES). These copper-based titanate materials were exploited to fabricate the enzymeless glucose sensors, and their assay performances to glucose were evaluated by conventional electrochemical techniques. Cyclic voltammetry (CV) and chronoamperometry (I–t) revealed a high sensitivity, fast response, excellent stability, and good reproducibility in the glucose determination at +0.55 V. Under optimal conditions, the electrocatalytic response of the sensor was proportional to the glucose concentration in the range of 2.5 × 10−7 M to 8.0 × 10−3 M with a detection limit of 5.0 × 10−8 M (signal-to-noise = 3). Moreover, the intercalated copper electrode materials exhibited high stability and improved selectivity for glucose compared with the more apparently accessible copper. This work also provides a simply controlled test-bed for electrochemical functionalization of layered titanate for sensor applications.

This work demonstrated the use of self-assembled thin films of multi-walled carbon nanotubes (CNTs) in designing enzymeless glucose sensor. Well-dispersed self-assembled CNT were prepared based on the spontaneous and strong chemisorption of polyoxometalates on CNT surface. Electrostatically self-assembled CNT films interlaced with cationic polyelectrolyte binding layer were constructed and used to confine the growth of copper (Cu) metal particles by the pulsed electrodeposition technique. The morphology of electroplated Cu on the CNT film was confirmed by scanning electron microscopy (SEM), and Cu were deposited as uniformly dispersed individual particles rather than continuous film on the CNT substrate. Sensing and assay performance of the copper deposits on CNT films to glucose were evaluated in detail. Cyclic voltammetry (CV), chronoamperometry (I–t) and flow injection amperometry (FIA) revealed a high sensitivity, excellent stability, and good reproducibility in the glucose determination. The current response of the sensor reached 602.04 μA mM−1 cm−2 with enough high signal to noise ratios at various glucose concentration levels, which was superior than those of Cu electrodeposition on CNT reported so far. A detection limit of 1.0 × 10−7 M (signal-to-noise = 3) and a linear range of 5.0 × 10−7 to 1.8 × 10−3 M were obtained. Present study provides a low cost and simply controlled test-bed for fundamental study on using self-assembled CNT films for sensor fabrication.

•Ultrathin MoS2 nanosheets with narrow band gap were thermolytically achieved.•The MoS2 is used as a high visible light sensitive material for PEC sensing.•The detection limit for glucose is much lower than other similar configurations.•The feasibility of determining glucose in human serum is demonstrated.For the purpose of effectively utilizing the visible light, photoelectrochemical (PEC) detection represents a unique detection signal and different energy form of the excitation source. In this work, ultrathin MoS2 nanosheets with narrow band gap were successfully fabricated by a facile C3N4 sacrificial template assisted thermolytical approach. Upon immobilizing glucose oxidase, excellent photocatalytic activity towards glucose is achieved in neutral buffer solution. As a novel visible light sensitive photocatalytic material, ultrathin MoS2 nanosheets present a detection limit of ~0.61 nM, which is much lower than those with the similar configurations reported previously. Based on the excellent anti-interference property, the feasibility of applying the proposed sensor to determine glucose in human serum is further demonstrated. This work provides new insight into the fabrication of promising visible light sensitive two-dimensional layered transition-metal chalcogenides nanostructures for construction of photoelectrochemical biosensors.

Controllable engineering of high-electronegativity oxygen (O)-heteroatoms into MoS2 ultrathin nanosheets is realized via a facile post-modification process. The incorporated oxygen atoms impart a dramatically enhanced ORR activity to the pristine nanosheets, with a 7.8-fold current increase as well as 180 mV and 160 mV positive shifts in both onset and half-wave potentials that are almost comparable with the commercial Pt/C catalyst. Furthermore, oxygen incorporation also triggers a transformation of the process from two-electron to a four-electron process. The improved topical conductivity, as well as the preferential adsorption of oxygen molecules originating from the heteroatoms engineering is supposed to be responsible for the efficient ORR. The prospect of controllably engineering heteroatoms into MoS2 ultrathin nanosheets with versatile applications is also highlighted in this work.

Ultrafine CuO nanoparticles (UCNs) were well-isolated in the nano-channels of ordered mesoporous carbon (OMC) via a double solvent procedure. In this approach, uniform OMC meso-channels of large surface area acted as nanoreactors embedded with small nanoparticles. n-Hexane was used as hydrophobic solvent to disperse OMC, and hydrophilic Cu(NO3)2 aqueous solution served as a precursor to fill the nano-channels. The interfacial force between double solvents of Cu(NO3)2 and n-hexane facilitated the precursor filling within the OMC mesopores, and the subsequent heat treatment triggered in situ isolation of UCNs within OMC porous channels. This final product was denoted as UCNs@OMC, and the structure and morphology of UCNs@OMC were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2-sorption. Increased glucose oxidation currents implied the accessibility of the active catalytic sites of UCNs@OMC, and an UCNs@OMC based glucose sensor was fabricated and tested exhibiting good reproducibility and selectivity.

Engineering phosphorus heteroatoms into the plane of ultrathin MoS2 nanosheets is realized via a facile thermolytical process. The doping of low-electronegative P atoms generates an extra ORR activity with four-electron selectivity, manifesting seven-fold current increase as well as 160 mV positive shift in both onset and half-wave potentials.

Water electrolysis has been considered as one of the most effective, secure and sustainable ways to produce clean hydrogen energy to resolve the looming energy and environmental crisis. Exploring bifunctional catalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with high efficiency, low cost, and easy integration is crucial for future renewable energy systems. Herein, we report the in situ controllable synthesis of hierarchical MoP/Ni2P heterostructures on 3D Ni foam (MoP/Ni2P/NF) and their application as an efficient bifunctional electrocatalyst for water splitting. The hierarchical heterostructures are achieved by a facile hydrothermal approach to obtain the Mo-based/NF precursor, followed by a subsequent in situ phosphorization procedure. Through manipulating the concentration of ammonium molybdate for the preparation of the precursor as well as the phosphorization temperature, the optimal MoP/Ni2P/NF can be achieved which can efficiently catalyze both the OER and HER in alkaline electrolytes. The superior performance with robust durability is mainly attributed to unique hierarchical heterostructures and collaborative advantages of bimetallic phosphides, as well as the 3D porous conductive substrate. As an integrated high-performance non-noble electrocatalyst for overall water splitting, the MoP/Ni2P/NF electrode requires a cell voltage of only 1.55 V to achieve a current density of 10 mA cm−2 in alkaline solution. This work highlights the importance of the design and construction of hierarchical heterostructures for efficient overall water splitting.

MoS2 nanodots (NDs) were successfully embedded in the three-dimensional (3D) porous frameworks of N-doped graphene (NGr) via in situ pyrolysis of glucose, a layered C3N4 sacrificial template and monolayered MoS2 NDs. The monolayered MoS2 NDs were hydrothermally pre-synthesized and acted as size-controlled precursors. By varying the content of the MoS2 NDs, a series of MoS2 NDs/NGr was obtained, which displayed amendable activity towards oxygen reduction reaction (ORR) in basic solution, due to the balance between the exposed edge sites of the MoS2 NDs and the internal conductive channels of the 3D porous NGr. The optimal composition generated an efficient Pt-free ORR catalyst with good four-electron selectivity, and was shown to have a more positive shift in both the onset and peak potentials than its counterparts. The novel catalyst also demonstrated superior tolerance against methanol and better durability than commercial Pt/C.

Uniform iron carbide nanoparticles (Fe3C, ∼10 nm), size evolved from nano-scaled Fe-MIL-88b, were one-pot pyrolytically embedded in 3D porous N-rich graphene. Extra ORR catalytic activity with four-electron selectivity was achieved in an alkaline electrolyte. The onset and peak potential were 10 mV and 40 mV more positive, respectively, than commercial Pt/C.