•Thermally exfoliated graphene oxide is controllably activated for supercapacitors.•Porous graphene materials exhibit tunable pore geometry and surface feature.•KOH-activated graphene shows 2D structure and high specific capacitance.•CO2-activated graphene shows 3D structure and excellent rate capability.•Relation between supercapacitive behaviors and structural properties are clarified.Improving the energy density of graphene-based electrical double-layer capacitors (EDLCs) with excellent rate capability requires a delicate construction to both ion-accessible surface and spatial architecture of graphene. In this work, two-dimensional (2D) and three-dimensional (3D) porous graphene architectures are controllably fabricated by two activation approaches (KOH, CO2) using identical thermally exfoliated graphene oxides as precursors and employed for systematically unravelling the governing principles of structural characteristics toward the corresponding supercapacitive performances. Under optimal conditions, the KOH-activated graphene appears as 2D lamellas with a bimodal micro-mesopore distribution and an ultra-high specific surface area of 2518 m2g-1, which gives a specific capacitance of 261 F g−1 and a capacitance retention of 98.5% at 5 A g−1 after 1000 cycles. In contrast, CO2-activated graphene shows 3D curly morphology with a hierarchical micro-meso-macroscopic structure and an ultra-large pore volume of 3.08 cm3g-1, where an excellent rate capability of 86.1% from 0.5 to 10 A g−1 can be implemented. It is demonstrated that the microporosity, specific surface area and surface wettability are the key factors to the capacitance, while the pore morphology and topology is responsible to the rate performances. Our results may offer critical insights into the rational design of activated graphene for supercapacitors.

•An inorganic phosphorous acid-modified mesoporous SBA-15 was synthesized.•The composite possessed high surface area, lager pore size and pore volume.•There were abundant and highly accessible binding sites present on its surface.•The composite exhibited an exceptional performance for Gd(III) adsorption.The development of rare earth adsorbent with high adsorption capacity and rapid adsorption rate is one of the most important issues for enriching and recovering rare earth ions. In the present work, an inorganic phosphorous acid-modified mesoporous SBA-15 (P-SBA-15) was facilely synthesized by a simple and cost-effective post-grafting approach, and its adsorption behavior towards the rare earth ion Gd(III) was investigated. Benefiting from high specific surface area (669.7 m2·g−1), large pore size (9.1 nm), and the presence of abundant phosphorous acid groups (1.4 mmol·g−1) on the surface, the P-SBA-15 exhibited an excellent performance in terms of capacity and kinetics on adsorption of Gd(III). Under optimized conditions, the adsorption capacity of P-SBA-15 towards Gd(III) was up to 1.3 mmol·g−1 at 30 °C, which is the second highest value as compared with previously reported Gd(III) adsorbents. Moreover, the adsorption of Gd(III) onto P-SBA-15 was ultrafast, achieving adsorption equilibrium within only 2 min. Test of reusability revealed that this mesoporous adsorbent could be repeatedly used several times without significant loss in binding capacity. This work not only provides a new insight into the fabrication of phosphorous acid-functionalized mesoporous silica, but also demonstrates its prospective application in adsorptive removal and/or recovery of rare earth ions.Download high-res image (143KB)Download full-size image

•N/P co-doped graphene is controllably prepared by one-step activation.•Increased oxygen functionalities on the precursor can facilitate N and P doping.•High volumetric capacitance and excellent rate and cycle performance are observed.•Enhanced energy density of 8.2 Wh kg−1 (4.6 Wh L−1) is obtained.Improving the energy density of carbon-based supercapacitors is one of the most urgent demands for developing high-power energy supplies, which in general requires delicate engineering of the carbon composition and textures. By pre-functionalization of graphene nanosheets and successive one-step (NH4)3PO4 activation, we prepared a type of nitrogen and phosphorus co-doped graphene (NPG) with high specific surface areas, hierarchical pore structures as well as tunable N and P contents. The as-obtained NPG shows high specific capacitances of 219 F g−1 (123 F cm−3) at 0.25 A g−1 and 175 F g−1 (98 F cm−3) at 10 A g−1, respectively. Accordingly, the NPG-based symmetrical supercapacitor device, working at a potential window of 1.3 V, could deliver an enhanced energy density of 8.2 Wh kg−1 (4.6 Wh L−1) at a power density of 162 W kg−1 (91 W L−1), which still retains 6.7 Wh kg−1 at 6.5 kW kg−1. In particular, under a current density of 5 A g−1, the device endows an 86% capacitance retention of initial after 20,000 cycles, displaying superior cycle stability. Our results imply the feasibility of NPG as a promising candidate for high-performance supercapacitors.Download high-res image (425KB)Download full-size image

•Oleic acid modified NiFe2O4 nanoparticles were prepared for catalytic aquathermolysis.•Fresh OA-NiFe2O4 catalyst implements high viscosity reduction rates of 87.5%.•The magnetically recycled OA-NiFe2O4 maintains impressive catalytic efficiency.We reported a magnetically recyclable oleic acid modified NiFe2O4 (OA-NiFe2O4) nanocatalyst via an economical solvothermal approach for catalytic aquathermolysis of Liaohe heavy oil. Under the set conditions (240 °C, 3 MPa, 24 h), 9.67% of the heavy components can be effectively converted to light components, leading to a satisfactory viscosity reduction rate of 87.5%. After 5 cycles, OA-NiFe2O4 could still maintain impressive catalytic efficiency to implement high viscosity reduction rate of beyond 80.0%. Structural, spectral and morphological characterizations show that, oleic acid can be attached to the surfaces of NiFe2O4 nanoparticles coordinatively, which prevents the nanoparticles from being aggregated, resulting in both excellent catalytic aquathermolysis performance and recycling durability. Our work provides a low-cost and magnetically recyclable catalyst candidate for reducing the viscosity of heavy oil via catalytic aquathermolysis.

The development of high-performance adsorbents for efficient removal of bilirubin from albumin-rich solution is still a considerable challenge. In this study, a magnetic nitrogen-doped porous carbon (m-NpC) was facilely synthesized through a simple one-pot route using the biomass chitosan and the iron salt Fe(NO3)3·9H2O as precursors, and NaCl as template agent, respectively. Intriguingly, the resulting m-NpC material showed a hierarchically micro–meso–macroporous structure, high surface area (289 m2 g−1), large pore volume (0.33 cm3 g−1), and good magnetic response. In particular, the basic site-rich surface of m-NpC obtained as a result of nitrogen doping could compete effectively with albumin for bilirubin binding. As such, the m-NpC was used as a magnetically separable bilirubin adsorbent and showed superior adsorption properties for bilirubin removal from a bovine serum albumin (BSA)-rich solution. Under optimized conditions, the maximum adsorption capacity of m-NpC was up to 72.4 mg g−1, which is significantly higher than the value achieved by magnetic non-nitrogen doped porous carbon (24.7 mg g−1), but also superior to those of many previously reported adsorbents for BSA-boned bilirubin removal. Moreover, as evidenced by hemolysis assay, this material exhibited only a negligible hemolysis effect. These results suggest that the composite developed in this work can be used as a promising adsorbent in blood purification application to mitigate the risk of excess bilirubin.

A novel waxberry-like SiO2@MnSiO3 core–shell nanocomposite was facilely fabricated via the simple one-step thermal treatment of SiO2 nanospheres, MnCl2·4H2O, ethylenediamine (EDA), and ethylene glycol (EG). Through an intensive investigation of the effects of Si/Mn molar ratio and reaction time on the grain growth characteristics, a self-template growth mechanism of SiO2@MnSiO3 was proposed. The self-template silica nanospheres released silicate anions slowly from their surfaces by alkali etching in the presence of EDA, and a fast precipitation reaction between Mn2+ cations and silicate anions occurred within the interfacial regions, eventually leading to the formation of a MnSiO3 shell on the surfaces of silica nanospheres. A well-defined waxberry-like SiO2@MnSiO3 nanostructure was obtained with a Si/Mn molar ratio of 5:1 and a reaction time of 10 h according to our experiments. Interestingly, this SiO2@MnSiO3 exhibited a high catalytic activity for oxidative degradation of methylene blue (MB); more than 93% of MB could be decomposed within 40 min. Moreover, it could also act as a potential adsorbent for efficient removal of Pb2+ ions from aqueous solution. The Pb2+ adsorption capacity was up to 50.5 mg g−1, which was significantly higher than those found for many other conventional adsorbents. Overall, this work not only provides a new insight into the fabrication of silica-supported MnSiO3 nanocomposites but also demonstrates their excellent performance in heterogeneous catalysis and adsorption.

We reported a rhombohedral Na-rich nickel hexacyanoferrate (r-NiHCF) with high discharge voltage, which also possesses long cycle stability and excellent rate capability when serving as the cathode material of Na-ion batteries. First-principles calculations suggest that the high working voltage of r-NiHCF is correlated to the asymmetric residence of Na+ ions in the rhombohedral framework in parallel with the low charge density at the Fe2+ ions. In both aqueous and ether-based electrolytes, r-NiHCF exhibits higher voltage than that of cubic NiHCF. Rate and cycle experiments indicate that r-NiHCF delivers a specific capacity of 66.8 mAh g–1 at the current density of 80 mA g–1, which is approximate to the theoretical capacity of r-NiHCF. A capacity retention of 96% can be achieved after 200 cycles. The excellent stability of r-NiHCF can be assigned to the absence of rhombohedral–cubic phase transition and negligible volume variation during electrochemical redox, as proven by the ex situ XRD patterns at different depths of charge/discharge and the DFT calculations, respectively.Keywords: cathode material; density functional theory study; high discharge voltage; mechanism; Na-ion batteries; rhombohedral nickel hexacyanoferrate;

Prohibiting lithium polysulfides from being dissolved to electrolyte is the most critical challenge for pursuing high-performance Li/S batteries. Taking full advantage of interactions between polysulfides and functional groups of third-party additives has been proven to be an efficient strategy. In the present work, we selected DNA to decorate CMK-3/S cathodes. The –PO and N– sites of the constituent deoxyribonucleotides of DNA are demonstrated to be capable of anchoring polysulfides through our DFT calculations. The experimental results show that adding a small amount of DNA into the CMK-3/S composite significantly improved the cyclic performance. In particular, with a moderate DNA loading rate, the DNA post-loading procedure resulted in a discharge capacity of 771 mA h g−1 at 0.1 C after 200 cycles (70.7% retention of the initial), which yielded slightly improved performance as compared to the DNA pre-loading procedure. The proposed DNA decorating scheme may provide an applicable technical solution for developing high-performance Li/S batteries.

A novel magnetic imprinting nanotechnology for selective capture of Gd3+ from a mixed solution of rare earth ions was developed by simply adding Gd3+-imprinted chitosan/carbon nanotube nanocomposite (IIP-CS/CNT) and silica-coated magnetite nanoparticle (SiO2@Fe3O4). The IIP-CS/CNT was prepared for the first time via a facile “surface deposition–crosslinking” method, exhibiting a well-defined coating structure. Interestingly, the neighboring IIP-CS/CNT monomers were held together as bundles, like a network, containing abundant interstitial spaces. When IIP-CS/CNT and SiO2@Fe3O4 were dispersed in a mixed solution of rare earth ions, the magnetic SiO2@Fe3O4 submicrospheres would be trapped in or adhere to the IIP-CS/CNT network, leading to the magnetization of IIP-CS/CNT; meanwhile, Gd3+ ions could be selectively captured by the magnetized IIP-CS/CNT. Saturation adsorption capacity for Gd3+ was up to 88 mg g–1 at 303.15 K, which is significantly higher than the Gd3+ adsorption capacities for the reported rare earth ion-imprinted adsorbents over recent years. The selectivity coefficients relative to La3+ and Ce3+ were 3.50 and 2.23, respectively, which are very similar to those found for other reported CS-based imprinted materials. Moreover, the imprinted adsorbents could be easily and rapidly retrieved by an external magnetic field without the need of additional centrifugation or filtration, greatly facilitating the separation process. Test of reusability demonstrated that the magnetized IIP-CS/CNT could be repeatedly used without any significant loss in binding capacity. Overall, this work not only provides new insights into the fabrication of magnetic imprinted CS-based composite, but also highlights its application for selective adsorption toward rare earth ions.Keywords: Gd3+; imprinted nanocomposite; magnetically retrievable; selective adsorption;

We show that the amount of peroxide added is a governing factor, leading to the curved or amorphous morphologies of Mg–Al-LDH products in a reflux system under ambient pressure. A concerted growth mechanism is proposed to elucidate the formation of the unconventional nano-features of the products.

Stabilizing lithium polysulfides in cathodes via interactions between polysulfides and affinitive functional groups could prevent polysulfide dissolution, leading to suppressed “shuttle effect” of lithium/sulfur (Li/S) batteries. Herein, four deoxynucleotides (DNs), including A (adenine-DN), T (thymine-DN), G (guanine-DN), and C (cytosine-DN), which own rich polysulfide affinitive groups, are selected to model the anchoring environments of polysulfides. Using the most soluble Li2S8 as probe, our first-principles simulations suggest that the interactions between polysulfides and substrates are highly correlated to the charges of affinitive sites, H-bonding environments and structural tension. The contributions from each type of interactions are quasi-quantitatively assessed. The electrostatic attractions between Li+ and the strong electron lone-pairs dominate the adsorption energetics, while the H-bonds formed between S82– and substrate give rise to excessive stabilization. In contrast, structural distortion or rearrangement of the substrates is detrimental to the anchoring strengths. The quasi-quantitative resolution on the different interaction modes provides a facile and rational scheme for screening more efficient polysufide affinitive additives to sustain the cathode cyclicity of Li/S batteries.

•AuNPs/uTiO2 was prepared via photoreduction deposition of Au nanoparticles (AuNPs) on urchin-like TiO2 nanosphere (uTiO2).•AuNPs/uTiO2 showed high surface area (147.5 m2 ⋅ g-1), large pore volume (0.52 cm3 ⋅ g-1), and high dispersity of AuNPs.•uTiO2 support could prevent leaching or aggregation of AuNPs, while allowing guest molecules to diffuse in and out easily.•AuNPs/uTiO2 exhibited superior catalytic efficiencies for dyes degradation and 4-nitrophenol reduction.•Catalytic activity of AuNPs/uTiO2 could remain almost unchanged after being recycled for several times.The development of efficient heterogeneous catalysts for degrading organic pollutants or converting them into harmless and even useful products is of vital significance for environmental remediation. Herein, we reported the facile synthesis of a highly active and stable nanocatalyst (AuNPs/uTiO2) via a simple photoreduction deposition of Au nanoparticles (AuNPs) on urchin-like TiO2 nanosphere (uTiO2), and demonstrated its excellent performances as a catalyst for oxidative degradation of organic dyes and reductive conversion of 4-nitrophenol (4-NP). The AuNPs/uTiO2 nanocomposite showed high surface area (147.5 m2·g− 1), large pore volume (0.52 cm3·g− 1), and high dispersity of AuNPs. In particular, the uTiO2 support could combine AuNPs strongly and serve as a shield to prevent leaching or aggregation of AuNPs, while allowing guest organic molecules to diffuse in and out easily. Benefiting from the excellent characteristics, the AuNPs/uTiO2 exhibited superior catalytic properties for dyes degradation and 4-NP reduction with significantly higher catalytic efficiencies than many previously reported heterogeneous catalysts. Moreover, the catalytic activity of AuNPs/uTiO2 could remain almost unchanged after being recycled for several times, demonstrating its long-term stability. The AuNPs/uTiO2, combining the advantages of high activity, favorable kinetics, and excellent durability for dye degradation and 4-NP reduction, should be very promising for wastewater treatment.Download high-res image (137KB)Download full-size image

•Hollow mesoporous silica spheres (HMSS) were facilely decorated by MnSiO3.•Such decoration method is simple, efficient, and scalable.•The resulting product well preserved morphological and textural features of HMSS.•The product showed excellent performance in both catalysis and adsorption.In this work, the MnSiO3 decorated hollow mesoporous silica spheres (MHMSS) was facilely synthesized via an one-step thermal treatment of hollow mesoporous silica spheres (HMSS) and MnCl2⋅4H2O in a binary solvents (ethylenediamine/ethylene glycol). Intriguingly, it was found that MnSiO3 nanocrystals were formed effectively on the pore surface of HMSS without pore blocking, and the resultant MHMSS fully inherited the morphological and textural characteristics of HMSS such as spherical hollow structure with mesoporous shell, large pore size (mainly distributed around 15.5 nm), high surface area (501.5 m2 g−1), and large pore volume (1.85 cm3 g−1). More importantly, the MHMSS exhibited high catalytic activities for oxidative degradation of methylene blue (MB), basic red 5 (BR), and rhodamine B (RhB) in the presence of H2O2. Typically, 10 mL of MB (50 mg L−1) can be decolored by 80% in 1 min and nearly 93% in 10 min. Moreover, the MHMSS also showed excellent adsorption properties in term of capacity and kinetics on removal of Pb2+. The Pb2+ adsorption could reach equilibrium within 100 min, and the maximum adsorption amount was up to 279.4 mg g−1 at 313.15 K, significantly higher than those found for many other adsorbents. The present results suggest that the MHMSS hybrid material can not only be used as a superior heterogeneous catalyst for degradation of organic contaminants, but also act as a highly efficient adsorbent for adsorptive removal of heavy metal ions, which may provide insight into the design and development of high-efficiency nanomaterials and nanotechnologies for environmental remediation.

Prohibiting lithium polysulfides from being dissolved to electrolyte is the most critical challenge for pursuing high-performance Li/S batteries. Taking full advantage of interactions between polysulfides and functional groups of third-party additives has been proven to be an efficient strategy. In the present work, we selected DNA to decorate CMK-3/S cathodes. The –PO and N– sites of the constituent deoxyribonucleotides of DNA are demonstrated to be capable of anchoring polysulfides through our DFT calculations. The experimental results show that adding a small amount of DNA into the CMK-3/S composite significantly improved the cyclic performance. In particular, with a moderate DNA loading rate, the DNA post-loading procedure resulted in a discharge capacity of 771 mA h g−1 at 0.1 C after 200 cycles (70.7% retention of the initial), which yielded slightly improved performance as compared to the DNA pre-loading procedure. The proposed DNA decorating scheme may provide an applicable technical solution for developing high-performance Li/S batteries.