Electrodeposited nickel–iron–carbon–molybdenum film as efficient bifunctional electrocatalyst for overall water splitting in alkaline solution

Designing and synthesizing of efficient and inexpensive bifunctional electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is one of the current research topics. In this study, NiFeCMo film in nickel mesh substrate is prepared by one-step direct-current electrodeposition method. The obtained NiFeCMo film shows the excellent electrocatalytic activity, which only requires overpotentials of 254 mV for HER and 256 mV for OER to drive current density of 10 mA cm⁻², with corresponding Tafel slopes of 163.9 and 60.3 mV·dec⁻¹ in 30% KOH medium, respectively. Moreover, NiFeCMo film only needs a low cell voltage of 1.61 V to drive current density of 10 mA cm⁻² in an alkaline electrolyzer. Such remarkably HER and OER properties of NiFeCMo alloy is attributed to the increased effective electrochemically active surface area and the synergy effect among Ni, Fe, C and Mo.     

Flower-like CoS2/MoS2 nanocomposite with enhanced electrocatalytic activity for hydrogen evolution reaction

Molybdenum sulfide (MoS₂) has received tremendous attracts for its promising performance in the aspects of hydrogen evolution reaction (HER). To improve the HER activity of MoS₂, we designed a flower-shaped CoS₂/MoS₂ nanocomposite with enhanced HER electroactivity compared with MoS₂ nanosheets by a simple one-step hydrothermal method. The facile approach brings about distinct transformation of the morphology from nanosheets to nanoflower structures. The introduction of Co element into MoS₂ results in the larger active surface area, more edge-terminated structures, and higher conductivity of the CoS₂/MoS₂ nanocomposite, which are good for improving the HER electroactivity. In brief, the optimized catalyst exhibits the low overpotential of 154 mV at 10 mA cm^?2, small Tafel slope of 61 mV dec^?1, and excellent stability in acidic solution.     

Controlled synthesis of NiCoM (M=P,S, Se,O)–Ni3S2–MoS2 hybrid material as environmentally friendly water splitting catalyst

The study of high efficiency and low cost catalysts is of great significance to the overall development of electrochemistry. In this paper, NiCoM (M = P, S, Se, O)–Ni₃S₂–MoS₂ hybrid material was prepared by hydrothermal, calcination and hydrothermal three-step reaction method, and its hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline environment were studied and compared. The experimental results showed that at 10 mA cm^?2, the overpotential of NiCoP–Ni₃S₂–MoS₂ was only 140 mV for HER, while the overpotential of NiCoSe–Ni₃S₂–MoS₂ was only 160 mV for OER. Compared with other catalysts, the activity of NiCoP–Ni₃S₂–MoS₂ and NiCoSe–Ni₃S₂–MoS₂ was higher, and the chemical reagents needed for preparation were cheap and low cost. What is noteworthy is that the morphology of NiCoP–Ni₃S₂–MoS₂ material change after long time stability test for hydrogen evolution reaction, the change makes the performance of the samples toward a better direction. A series of characterization found that the surface of the NiCoP–Ni₃S₂–MoS₂ samples increased more holes and more active site, and did not produce new material after other characterization. Density functional theory calculation shows that the presence of this MoS₂ material accelerates the kinetics of hydrogen production and this Co₂P material enhances the conductivity of the material. Their synergistic effect makes the NiCoP–Ni₃S₂–MoS₂ catalyst exhibit enhanced hydrogen production activity. The bramble structure of NiCoSe–Ni₃S₂–MoS₂ allows the sample to have more active sites and higher electrocatalytic activity during the OER process. This experiment provides new insights into the preparation of robust water splitting catalysts by simple methods.     

Porous CoS2 nanostructures based on ZIF-9 supported on reduced graphene oxide: Favourable electrocatalysis for hydrogen evolution reaction

The research and developments of porous, highly active non-noble metal cathode materials are the current hot spots. In our work, ZIF-9 (Zeolitic imidazolate framework-9) as a cobalt source provide porous structure, we have sulfurized the ZIF-9 into CoS₂ by a simple hydrothermal method. Ultimately, the porous CoS₂/RGO cathode material was obtained. Through a series of characterization analyses (powder X-ray diffraction, X-ray photoelectron spectroscopy), it is confirmed that the CoS₂/RGO composite was successfully formed. Furthermore, electrochemical tests demonstrated that the pursued catalyst exhibited remarkable hydrogen evolution reaction (HER) activities with a favorable overpotential (only 180 mV for 10 mA cm^?2 vs reversible hydrogen electrode), a low Tafel slopes (75 mV decade^?1) and high stability in acidic condition (more than 18 h).     

Inhibitor-regulated corrosion strategy towards synthesizing cauliflower-like amorphous RuFe-hydroxides as advanced hydrogen evolution reaction catalysts

Producing clean hydrogen energy by water electrolysis is considered as an effective route to solve the current energy and environmental problems. Herein, a facile inhibitor-regulated corrosion strategy is employed to synthesize efficient hydrogen evolution reaction (HER) catalysts. The corrosion inhibitor of D-sodium gluconate (SG) is adopted to slow down the serious reaction of iron foam (IF) in RuCl₃ aqueous solution. It is identified that the abundant hydroxy and carboxyl species of SG can compete with Cl^? to adsorb on the IF surface to weaken the drastic reaction between Ru³⁺ and IF, resulting in achieving uniform amorphous RuFe(OH)_x corrosion layers composed of nanoparticle aggregations. Owing to the sufficient exposure of active sites and electronic interaction between Ru and Fe sites, the optimized catalyst exhibits excellent HER activity of requiring a lower potential of 91 mV to reach a current density of 100 mA cm^?2 and maintains durable operation at 100 mA cm^?2 for 30 h without obvious fluctuations. This work supplies a facile inhibitor-regulated corrosion strategy for designing efficient catalysts for water splitting application.     

Ni2P(O)–Fe2P(O)/CeOx as high effective bifunctional catalyst for overall water splitting

The development of cost-effective bifunctional catalysts with excellent performance and good stability is of great significance for overall water splitting. In this work, NiFe layered double hydroxides (LDHs) nanosheets are prepared on nickel foam by hydrothermal method, and then Ni₂P(O)–Fe₂P(O)/CeO_x nanosheets are in situ synthesized by electrodeposition and phosphating on NiFe LDHs. The obtained self-supporting Ni₂P(O)–Fe₂P(O)/CeO_x exhibit excellent catalytic performances in alkaline solution due to more active sites and fast electron transport. When the current density is 10 mA cm^?2, the overpotential of hydrogen evolution reaction and oxygen evolution reaction are 75 mV and 268 mV, respectively. In addition, driven by two Ni₂P(O)–Fe₂P(O)/CeO_x electrodes, the alkaline battery can reach 1.45 V at 10 mA cm^?2.     

Novel 3-D urchin-like Ni– Co–W porous nanostructure as efficient bifunctional superhydrophilic electrocatalyst for both hydrogen and oxygen evolution reactions

Fabrication of an electrocatalyst with remarkable electrocatalytic activity for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is important for the production of hydrogen energy. In this study, Ni–Co–W alloy urchin-like nanostructures were fabricated by binder-free and cost-effective electrochemical deposition method at different applied current densities and HER and OER electrocatalytic activity was studied. The results of this study showed that the microstructure and morphology are strongly influenced by the electrochemical deposition parameters and the best electrocatalytic properties are obtained at the electrode created at the 20 mA.cm⁻²applied current density. The optimum electrode requires −66 mV and 264 mV, respectively, for OER and HER reactions for delivering the 10 mA cm⁻² current density. The optimum electrode also showed negligible potential change after 10 h electrolysis at 100 mA cm⁻², which means remarkable electrocatalytic stability. In addition, when this electrode used as a for full water splitting, it required only 1.58 V to create a current density of 10 mA cm⁻². Such excellent electrocatalytic activity and stability can be related to the high electrochemical active surface area, being binder-free, high intrinsic electrocatalytic activity and hydrophilicity. This study introduces a simple and cost-effective method for fabricating of effective electrodes with high electrocatalytic activity.