It is of great importance but still remains a key challenge to develop non-noble-metal bifunctional catalysts for efficient full water splitting under mild pH conditions. In this communication, we report the in situ electrochemical development of an ultrathin Ni–Bi layer on a metallic Ni3N nanosheet array supported on a Ti mesh (Ni3N@Ni–Bi NS/Ti) as a durable 3D core/shell structured nanoarray electrocatalyst for water oxidation at near-neutral pH. The Ni3N@Ni–Bi NS/Ti demands overpotentials of 405 and 382 mV to deliver a geometrical catalytic current density of 10 mA cm−2 in 0.1 and 0.5 M K–Bi (pH: 9.2), respectively, superior in activity to Ni3N NS/Ti and most reported non-precious metal catalysts under benign conditions. It also performs efficiently for the hydrogen evolution reaction requiring an overpotential of 265 mV for 10 mA cm−2 and its two-electrode electrolyser affords 10 mA cm−2 at a cell voltage of 1.95 V in 0.5 M K–Bi at 25 °C.

Ammonia borane (AB) has been regarded as a promising candidate for chemical hydrogen storage but needs an efficient catalyst for hydrolytic hydrogen generation. In this communication, a CoP nanoarray in situ grown on a Ti mesh (CoP NA/Ti) is reported as a robust non-noble-metal catalyst for effective hydrogen generation from AB hydrolysis. The initial turnover frequency and activation energy of CoP NA/Ti for AB hydrolysis are 42.8 molH2 molCoP−1 min−1 and 34.1 kJ mol−1, respectively. Moreover, this catalyst shows only 0.15% loss in catalytic activity after 10 cycles and its easy separation nature from fuel solution enables its attractive use as an on/off switch toward on-demand hydrogen generation. The amazing catalytic activity and high durability of such a catalyst are attributed to the fact that the 3D nanoarray configuration not only allows for more efficient diffusion of the fuel and hydrogen gas but favors the exposure of more active sites, and on the other hand, in situ growth of CoP on a Ti mesh also ensures strong adhesion between them.

It is of high importance to design efficient electrocatalysts for the oxygen evolution reaction (OER) at alkaline pH. In this communication, we report the development of a Zn-doped Ni3S2 nanosheet array on Ni foam (Zn-Ni3S2/NF) as a high-performance and durable electrocatalyst for the OER. Such Zn-Ni3S2/NF drives a catalytic current density of 100 mA cm−2 with the requirement of an OER overpotential of 330 mV, 90 mV less than that for Ni3S2/NF. Furthermore, Zn-Ni3S2/NF demonstrates excellent long-term electrochemical durability maintaining its activity at an overpotential of 300 mV for 20 h.

Developing highly efficient and non-noble-metal catalysts is of great importance for electrochemical energy storage and conversion. In this communication, we report the development of a porous Ni3N nanosheet array on carbon cloth (Ni3N NA/CC) as a high-performance and durable electrocatalyst for urea oxidation. To drive 10 mA cm−2, this Ni3N NA/CC only demands a potential of 1.35 V in 1.0 M KOH with 0.33 M urea. The high catalytic activity of the hydrogen evolution reaction enables Ni3N NA/CC as a bifunctional catalyst electrode for electrochemical hydrogen production and the two-electrode electrolyzer is capable of offering 10 mA cm−2 at a cell voltage of only 1.44 V, 120 mV less than that for the urea-free counterpart.

•CoO/CC was used for effective NaBH4 hydrolysis in alkaline media.•CoO/CC shows high a hydrogen generation rate of 5955.29 mL/min/gCoO.•CoO/CC exhibits high recyclability and durability.•CoO/CC works as an on/off switch for on-demand hydrogen generation.In this work, we demonstrate the first use of cobalt oxide nanosheet array on carbon cloth (CoO/CC) as an efficient catalyst for the dehydrogenation of NaBH4. This catalyst shows a low activation energy of 35.40 kJ/mol for NaBH4 hydrolysis and the hydrogen generation rate at 30 °C can reach up to 5955.29 mL/min/gCoO. Moreover, the catalyst exhibits high recyclability and durability. It suggests that the hydrolysis kinetics depends on many parameters, including temperature, NaBH4 concentration, NaOH concentration and mass of catalyst.Download high-res image (353KB)Download full-size image

AbstractWe report the development of a cobalt phosphide nanoarray as an efficient and stable catalyst for the hydrazine oxidation reaction (HzOR) in alkaline media. Its high hydrogen evolution reaction (HER) activity enables it to be used as a bifunctional catalyst for less energy-intensive electrolytic hydrogen generation by replacing the sluggish oxygen evolution reaction with HzOR. The corresponding two-electrode electrolyzer using such a nanoarray as both the anode for HzOR and the cathode for HER only needs a cell voltage of 0.2 V to drive 10 mA cm−2 in 1.0 M KOH with 100 mM hydrazine, which is 1.45 V less than that for pure water splitting. This electrolyzer also shows strong long-term electrochemical durability with nearly 100 % faradic efficiency for hydrogen evolution.

In this communication, we report that a Co-doped NiSe2 nanoparticles film electrodeposited on a conductive Ti plate (Co0.13Ni0.87Se2/Ti) behaves as a robust electrocatalyst for both HER and OER in strongly basic media, with good activity over a NiSe2/Ti counterpart. This Co0.13Ni0.87Se2/Ti catalytic electrode delivers 10 mA cm−2 at an overpotential of 64 mV for HER and 100 mA cm−2 at an overpotential of 320 mV for OER in 1.0 M KOH. A voltage of only 1.62 V is required to drive 10 mA cm−2 for the two-electrode alkaline water electrolyzer using Co0.13Ni0.87Se2/Ti as an anode and cathode.

Hydrogen can be catalytically generated on a large scale by hydrolysis of NaBH4. In this communication, we describe the development of cobalt phosphide nanosheet arrays on Ti mesh (CoP/Ti mesh) as a robust and highly active monolithic catalyst for the hydrolytic dehydrogenation of NaBH4 in alkaline solutions. A hydrogen generation rate of 6100 mL(H2) min−1 g(CoP)−1 and an activation energy of 42.01 kJ mol−1 were achieved under air-saturated atmospheric conditions, which are superior to those of most reported catalysts, with good durability and reusability.

Ammonia borane (AB) has been considered as one of the most attractive candidates for chemical hydrogen-storage materials; it is highly desirable but still remains a huge challenge to design and develop highly active robust non-noble-metal catalysts for on-demand hydrogen generation from AB. In this work, we demonstrate that a Ni2P nanosheet array integrated on 3D Ni foam is highly active and robust for the hydrolytic dehydrogenation of AB. This monolithic catalyst behaves as an on/off switch for on-demand hydrogen generation with a large initial turnover frequency of 42.3 mol(H2) mol(Ni2P)−1 min−1 and a lower activation energy of 44.0 kJ mol−1 under ambient conditions, outperforming all reported Ni-based noble-metal-free catalysts and some noble-metal catalysts.

In this contribution, we demonstrate that electrodeposited nickel diselenide nanoparticles based film on conductive Ti plate (NiSe2/Ti) is an efficient and robust electrode to catalyze both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in basic media. Electrochemical experiments show this electrode affords 10 mA cm–2 at HER overpotential of 96 mV and 20 mA cm–2 at OER overpotential of 295 mV with strong durability in 1.0 M KOH. The corresponding two-electrode alkaline water electrolyzer requires a cell voltage of only 1.66 V to achieve 10 mA cm–2 water-splitting current. This development provides us an attractive non-noble-metal catalyst toward overall water splitting applications.Keywords: electrodeposition; hydrogen; nanoparticles film; nickel diselenide; water splitting

•Ni promoted CoS2 nanowire array acts as a bifunctional water-splitting catalyst.•Ni2.3%-CoS2/CC exhibits high catalytic activity in basic media.•Ni2.3%-CoS2/CC maintains strong electrochemical durability in basic media.Development of efficient noble metal-free bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is an ongoing challenge. Herein, we report the development of nickel promoted cobalt disulfide nanowire array supported on carbon cloth (Ni2.3%-CoS2/CC) as an efficient bifunctional electrocatalyst for water splitting with superior activity and good durability in basic media. This Ni2.3%-CoS2/CC electrode delivers 100 mA cm− 2 at overpotential of 231 mV for HER and 100 mA cm− 2 at overpotential of 370 mV for OER. The water electrolyzer based on Ni2.3%–CoS2/CC only requires a cell voltage of 1.66 V to afford 10 mA cm− 2, implying the great potential for water splitting applications.

In this communication, we report that Ni–Co–S film electrochemically deposited on Cu foam (Ni–Co–S/CF) behaves as a bifunctional catalyst for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with good durability in strongly basic electrolyte. This 3D electrode behaves high activity of 10 mA cm−2 at overpotential of 140 mV for HER and 100 mA cm−2 at overpotential of 363 mV for OER in 1.0 M KOH. Furthermore, using Ni–Co–S/CF as both anode and cathode can afford 10 mA cm−2 at cell voltage of 1.67 V toward overall water splitting in alkaline solution.

Cost-effective bifunctional oxygen- and hydrogen-evolving electrocatalysts made from earth-abundant elements are crucial for efficient water splitting. In this communication, we report a versatile and one-step electrodeposition of NiFe nanosheets film on Ni foam (NiFe/NF) as a bifunctional catalytic material with high activity and stability for overall water splitting in basic electrolytes. The two-electrode electrolyzer using NiFe/NF as both anode and cathode can afford current density of 10 mA cm−2 at a cell voltage of 1.64 V, which stimulates the design and development of transition metal alloy nanostructures as attractive bifunctional catalysts for electrochemical production of hydrogen fuels.

The present communication reports the topotactic conversion of NiCo2O4 nanowires array on carbon cloth (NiCo2O4 NA/CC) into NiCo2S4 NA/CC, which is used as an efficient bifunctional electrocatalyst for water splitting with good durability and superior activity in 1.0 M KOH. This NiCo2S4 NA/CC electrode produces 100 mA cm−2 at an overpotential of 305 mV for hydrogen evolution and 100 mA cm−2 at an overpotential of 340 mV for oxygen evolution. To afford a 10 mA cm−2 water-splitting current, the alkaline water electrolyzer made from NiCo2S4 NA/CC needs a cell voltage of 1.68 V, which is 300 mV less than that for NiCo2O4 NA/CC, and has good stability.

It is attractive but still remains a big challenge to develop non-noble metal bifunctional electrocatalysts efficient for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) under alkaline conditions. Herein, an amorphous CoSe film electrodeposited on a Ti mesh (a-CoSe/Ti) is demonstrated to exhibit high electrocatalytic activity and stability for both reactions in 1.0 M KOH. It needs overpotentials of 292 and 121 mV to drive 10 mA cm−2 for OER and HER, respectively. The two-electrode alkaline water electrolyzer affords a water-splitting current of 10 mA cm−2 at a cell voltage of 1.65 V. This work offers an attractive cost-effective catalytic material toward full water splitting applications.

In this Letter, we describe the development of a CoSe2 nanowires array on carbon cloth (CoSe2 NW/CC) through a facile two-step hydrothermal preparative strategy. As a novel 3D nanoarray electrode for electrochemical hydrogen evolution, CoSe2 NW/CC exhibits excellent catalytic activity and durability in acidic media. It needs overpotentials of 130 and 164 mV to approach 10 and 100 mA cm–2, respectively, and its activity is maintained for at least 48 h. This work would open up new avenues for the rational design of a variety of arrayed transition-metal chalcogenide cathodes for technological application toward large-scale hydrogen generation from water.Keywords: anion exchange reaction; array electrode; CoSe2 nanowires; electrocatalysis; hydrogen evolution

In this communication, we report on the first use of Ni3Se2 film electrochemically deposited on Cu foam (Ni3Se2/CF) as a bifunctional catalyst for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with good durability at alkaline media. This 3D electrode exhibits high activity of 10 mA cm−2 at 100 mV HER overpotential and 50 mA cm−2 at 340 mV OER overpotential. A Ni3Se2/CF-based two-electrode alkaline water splitting system affording 10 mA cm−2 at a cell voltage of 1.65 V is also demonstrated successfully.

In this paper, we report on development of 3D macroporous MoS2 thin film on Mo foil (MoS2/Mo) by hydrothermal treatment of Mo foil in the presence of thiourea as an integrated hydrogen evolution cathode. Under acidic condition, the MoS2/Mo electrode exhibits good catalytic activity needing overpotentials of 168 and 215 mV to achieve current densities of 10 and 100 mA cm−2, respectively, and its activity is preserved for at least 17 h. Remarkably, it also performs well in both neutral and alkaline solutions.

In this paper, we demonstrate the first preparation of NiS2 nanosheets array on carbon cloth (NiS2 NA/CC) via sulfidization of its Ni(OH)2 NA/CC precursor. As a 3D hydrogen evolution cathode, the NiS2 NA/CC electrode shows excellent catalytic activity and stability in neutral solutions. It needs overpotentials of 193 and 243 mV to afford current densities of 2 and 10 mA/cm2, respectively. This electrode also works efficiently in basic solutions.

Urea electrolysis has shown great potential in hydrogen production and remediation of urea-containing wastewater and it is highly important to develop efficient urea oxidation electrocatalysts made from earth-abundant elements. Here we report the growth of NiMoO4·xH2O nanosheet arrays on Ni foam (NiMoO4 NAs/NF) through a hydrothermal process. When directly used as a 3D catalytic anode for electrooxidation of urea in alkaline solutions, the NiMoO4 NAs/NF exhibits high catalytic activity and stability. It achieves specific current density of 830 mA cm−2 mg−1 at 0.5 V at a scan rate of 10 mV s−1, about 4.2 times enhancement compared to Ni(OH)2 NAs/NF.

•NiFe foam behaves as an active 3D oxygen evolution anode in strongly basic solution.•NiFe foam exhibits strong long-term electrochemical durability.•Further acid etching leads to greatly enhanced catalytic activity.In this communication, we report the first use of commercial nickel–iron (NiFe) foam as a novel three-dimensional anode for oxygen evolution reaction in alkaline electrolyte. The NiFe foam electrode exhibits onset overpotential of 300 mV and affords current density of 10 mA cm−2 at an overpotential of 320 mV, with catalytic activity being maintained for at least 10 h. Further acid etching of this electrode leads to greatly enhanced OER activity.

•Ni3S2/Ni foam was developed as hydrogen-evolving cathode in neutral and basic media.•This electrode exhibits high catalytic activity.•This electrode shows good durability in a long-term electrochemical process.In this communication, we demonstrate for the first time that nickel sulfide nanosheets array supported on Ni foam can be used as an inexpensive three-dimensional electrocatalyst toward the hydrogen evolution reaction in both neutral and basic solutions. The Ni3S2/Ni foam served as an inexpensive, highly active and stable electrode material for water electrolysis. It needs overpotentials of 220 and 396 mV to afford current densities of 10 and 100 mA cm−2 in neutral media and needs overpotentials of 123 and 260 mV to afford current densities of 10 and 100 mA cm−2 in basic solutions.

Developing non-noble-metal hydrogen evolution reaction electrocatalysts with high activity is critical for future renewable energy systems. The direct growth of active phases on current collectors not only eliminates using polymer binder but also offers time-saving preparation of electrode. In this Letter, we develop self-supported FeP nanorod arrays on carbon cloth (FeP NAs/CC) via low-temperature phosphidation of its Fe2O3 NAs/CC. As a novel 3D hydrogen evolution cathode in acidic media, the FeP NAs/CC exhibits high catalytic activity and only needs an overpotential of 58 mV to afford current density of 10 mA/cm2. This electrode also works efficiently in both neutral and alkaline solutions.Keywords: 3D hydrogen evolution cathode; binder-free; electrocatalysis; FeP; nanorod arrays; water splitting

Designng efficient hydrogen evolution reaction (HER) electrocatalyst made from earth-abundant elements is essential to the development of water-splitting devices. In this communication, we described our recent effort to develop N-doped carbon nanotube supported FeP nanocomposites (FeP/NCNT) for HER. Experiments demonstrated that the FeP/NCNT is highly active toward the HER with onset overpotential of 66 mV, a Tafel slope of 59 mV dec−1, and a Faradaic efficiency close to 100% in acidic solutions. It needs overpotentials of 113 and 195 mV to afford current densities of 10 and 100 mA cm−2, respectively.

•Hematite nanorods array is developed on carbon cloth as a 3D oxygen evolution anode•This electrode shows an overpotential of 330 mV and a Tafel slope of 52 mV dec− 1•This electrode maintains its catalytic activity for at least 10 hIn this communication, hematite nanorods array is developed on carbon cloth (α-Fe2O3 NA/CC) as a novel anode for oxygen evolution reaction in alkaline electrolytes. This integrated 3D electrode exhibits an onset overpotential of 330 mV and a Tafel slope of 52 mV dec− 1 and its catalytic activity is superior over preformed α-Fe2O3 nanorods immobilized on CC using a polymer binder. Furthermore, this electrode affords current density of 10 mA cm− 2 at an overpotential of 420 mV and is capable of maintaining its catalytic activity for at least 10 h.

The detection of glucose plays a significant role in diagnostics and management of diabetes and it is thus desired to develop non-noble-metal electrocatalyst for nonenzymatic glucose sensing. This work demonstrates the first use of monolithically integrated copper phosphide nanowire on copper foam (Cu3P NW/CF) as an efficient catalyst for electrochemical oxidation of glucose. As a nonenzymatic glucose sensor, this Cu3P NW/CF exhibits a low detection limit of 0.32 μM at a signal-to-noise ratio of 3 with a linear range from 0.005 to 1 mM (R2 = 0.997). It also shows high anti-interference property to other normally co-existing electroactive species including lactose, fructose, ascorbic acid, uric acid, urea, dopiamine, and sucorse as well as excellent resistance to chloride poisoning. Its application for glucose detection in human serum sample is also demonstrated successfully.

It is of great importance but still remains a key challenge to develop non-noble-metal bifunctional catalysts for efficient full water splitting under mild pH conditions. In this communication, we report the in situ electrochemical development of an ultrathin Ni–Bi layer on a metallic Ni3N nanosheet array supported on a Ti mesh (Ni3N@Ni–Bi NS/Ti) as a durable 3D core/shell structured nanoarray electrocatalyst for water oxidation at near-neutral pH. The Ni3N@Ni–Bi NS/Ti demands overpotentials of 405 and 382 mV to deliver a geometrical catalytic current density of 10 mA cm−2 in 0.1 and 0.5 M K–Bi (pH: 9.2), respectively, superior in activity to Ni3N NS/Ti and most reported non-precious metal catalysts under benign conditions. It also performs efficiently for the hydrogen evolution reaction requiring an overpotential of 265 mV for 10 mA cm−2 and its two-electrode electrolyser affords 10 mA cm−2 at a cell voltage of 1.95 V in 0.5 M K–Bi at 25 °C.

It is attractive but still remains a big challenge to develop non-noble metal bifunctional electrocatalysts efficient for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) under alkaline conditions. Herein, an amorphous CoSe film electrodeposited on a Ti mesh (a-CoSe/Ti) is demonstrated to exhibit high electrocatalytic activity and stability for both reactions in 1.0 M KOH. It needs overpotentials of 292 and 121 mV to drive 10 mA cm−2 for OER and HER, respectively. The two-electrode alkaline water electrolyzer affords a water-splitting current of 10 mA cm−2 at a cell voltage of 1.65 V. This work offers an attractive cost-effective catalytic material toward full water splitting applications.

In this communication, we report on the first use of Ni3Se2 film electrochemically deposited on Cu foam (Ni3Se2/CF) as a bifunctional catalyst for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with good durability at alkaline media. This 3D electrode exhibits high activity of 10 mA cm−2 at 100 mV HER overpotential and 50 mA cm−2 at 340 mV OER overpotential. A Ni3Se2/CF-based two-electrode alkaline water splitting system affording 10 mA cm−2 at a cell voltage of 1.65 V is also demonstrated successfully.

Ammonia borane (AB) has been considered as one of the most attractive candidates for chemical hydrogen-storage materials; it is highly desirable but still remains a huge challenge to design and develop highly active robust non-noble-metal catalysts for on-demand hydrogen generation from AB. In this work, we demonstrate that a Ni2P nanosheet array integrated on 3D Ni foam is highly active and robust for the hydrolytic dehydrogenation of AB. This monolithic catalyst behaves as an on/off switch for on-demand hydrogen generation with a large initial turnover frequency of 42.3 mol(H2) mol(Ni2P)−1 min−1 and a lower activation energy of 44.0 kJ mol−1 under ambient conditions, outperforming all reported Ni-based noble-metal-free catalysts and some noble-metal catalysts.

Developing highly efficient and non-noble-metal catalysts is of great importance for electrochemical energy storage and conversion. In this communication, we report the development of a porous Ni3N nanosheet array on carbon cloth (Ni3N NA/CC) as a high-performance and durable electrocatalyst for urea oxidation. To drive 10 mA cm−2, this Ni3N NA/CC only demands a potential of 1.35 V in 1.0 M KOH with 0.33 M urea. The high catalytic activity of the hydrogen evolution reaction enables Ni3N NA/CC as a bifunctional catalyst electrode for electrochemical hydrogen production and the two-electrode electrolyzer is capable of offering 10 mA cm−2 at a cell voltage of only 1.44 V, 120 mV less than that for the urea-free counterpart.

Ammonia borane (AB) has been regarded as a promising candidate for chemical hydrogen storage but needs an efficient catalyst for hydrolytic hydrogen generation. In this communication, a CoP nanoarray in situ grown on a Ti mesh (CoP NA/Ti) is reported as a robust non-noble-metal catalyst for effective hydrogen generation from AB hydrolysis. The initial turnover frequency and activation energy of CoP NA/Ti for AB hydrolysis are 42.8 molH2 molCoP−1 min−1 and 34.1 kJ mol−1, respectively. Moreover, this catalyst shows only 0.15% loss in catalytic activity after 10 cycles and its easy separation nature from fuel solution enables its attractive use as an on/off switch toward on-demand hydrogen generation. The amazing catalytic activity and high durability of such a catalyst are attributed to the fact that the 3D nanoarray configuration not only allows for more efficient diffusion of the fuel and hydrogen gas but favors the exposure of more active sites, and on the other hand, in situ growth of CoP on a Ti mesh also ensures strong adhesion between them.

Hydrogen can be catalytically generated on a large scale by hydrolysis of NaBH4. In this communication, we describe the development of cobalt phosphide nanosheet arrays on Ti mesh (CoP/Ti mesh) as a robust and highly active monolithic catalyst for the hydrolytic dehydrogenation of NaBH4 in alkaline solutions. A hydrogen generation rate of 6100 mL(H2) min−1 g(CoP)−1 and an activation energy of 42.01 kJ mol−1 were achieved under air-saturated atmospheric conditions, which are superior to those of most reported catalysts, with good durability and reusability.