Design Of Ni-based Alloy Electrodes For Electrocatalytic Hydrogen Evolution Reaction

Hydrogen is considered as an ideal green energy and the primary alternative to fossil fuels for future energy supply.Electrochemical water splitting has been regarded to be a clean and efficient strategy to produce hydrogen.At present,one of the biggest challenges is the sluggish kinetics of electrocatalysts in hydrogen evolution reaction(HER).Pt-based materials are known as the most active electrocatalysts for HER.However,for commercial application,it has been severely limited by their scarcity and high cost.So,design of high-active and inexpensive transition metal based HER electrocatalyst plays a vital role in the development of sustainable hydrogen production.Although various non-noble metal catalysts have been reported for HER,their performance is not satisfactory compared with Pt-based materials.On this basis,we mainly focused on preparing binder-free Ni-based bimetallic alloy nanosheets electrocatalyst for HER,via topotactic transformation of layered nickel hydroxide salts(Ni-LHS).Moreover,we introduced V2O3 to promote the HER performence of alloy and explored the influence of localized surface plasmon resonance(LSPR)to HER performence of alloy-oxide hybrids.In summary,the main research contents are listed as follows:1.Preparation of layered nickel hydroxide salts and its derivatives:a general method to prepare binder-free Ni-based bimetallic alloy and alloy-oxide hybrid nanosheets is successfully developed for the first time,via topotactic transformation of Ni-LHS.It mainly included the preparation of various Ni-LHS by inserting different oxometallate anions into layered Ni(OH)2 by hydrothermal method.At the same time,various layered double nickel hydroxide salts(Ni-M-MoO42-LDHs)were prepared by inserting molybdate anions into different layered double nickel hydroxide(Ni-LDHs).By reducing these Ni-LHS and Ni-M-MoO42-LDHs nanosheets under hydrogen atmosphere,bimetallic Ni alloys and alloy-oxide hybrid nanosheets were obtained while keeping the initial nanosheets morphology during the topotactic transformation process.This topotactic transformation method using LHS and LDHs precursors provides a way to design and fabricate cost-effective and energy-efficient ultrathin 2D nanosheets for electrocatalysis,greatly broadening the scope of the currently available self-supporting electrocatalysts.2.Self-supporting Ni-based alloy nanosheets as superior pH-universal electrocatalysts for hydrogen evolution.The obtained bimetallic alloys show much improved HER performance to that of Ni.In particular,Ni4Mo alloy nanosheets exhibit HER activity with overpotential of only 69.6 mV at 100 mA cm-2 in alkaline medium,due to large electrochemical active surface area and low charge transfer resistance.Moreover,Ni4Mo alloy nanosheets also show high HER activity in both acidic and neutral electrolytes with long-term stability,demonstrating superior activity comparable to or better than state of the art commercial Pt/C catalyst.3.Divanadium trioxide enhances the electrocatalytic performance of Ni4Mo alloy for HER in neutral media.In this section,we present a combined theoretical and experimental approach to accelerate the sluggish HER kinetics of Ni4Mo alloy electrocatalysts through fabricating metal alloy-oxide hybrids.The V2O3 thus introduced can effectively reduce the kinetic energy barrier of the water-dissociation step.As a result,the developed Ni4Mo-V2O3 nanosheets show an extremely low HER overpotential of 39.3 mV at 10 mA cm-2 together with excellent long-term stability in neutral media.Near-ambient pressure X-ray photoelectron spectroscopy(NAP-XPS)further confirmed that the presence of V2O3 accelerated water dissociation on Ni4Mo-V2O3 surface.4.Boosting electrocatalytic hydrogen evolution over Ni4Mo-V2O3 hybrids by exciting the LSPR of V2O3.The V2O3 on Ni4Mo surface can efficiently lower the kinetic energy barrier of the initial water dissociation step.Meanwhile,LSPR of the V2O3 may also enhanced the HER performance of Ni4Mo-V2O3 hybrids.Based on the results in Section 2,we attempted to excite the LSPR of the V2O3 to further improve the HER performance of Ni4Mo in neutral media.Upon light irradiation,the Ni4Mo-V2O3 hybrids have obviously response to light.Meanwhile,light irradiation can effectively reduce the overpotential of Ni4Mo-V2O3 hybrids for HER in neutral media.In addition,the HER activation energy of Ni4Mo-V2O3 is significantly decreased due to the LSPR effect under light irradiation and thus the HER process can be driven more easily.