Molybdenum disulfide as hydrogen evolution catalyst:From atomistic to materials structure and electrocatalytic performance

Hydrogen production via water electrolysis defines the novel energy vector for achieving a sustainable society.However,the true progress of the given technology is hindered by the sluggish and complex hydrogen evolution reaction(HER)occurring at the cathodic side of the system where overpriced and scarce Pt-based electrocatalysts are usually employed.Therefore,efficient platinum group metals(PGMs)-free electrocatalysts to carry out HER with accelerated kinetics are urgently demanded.In this scenario,molybdenum disulfide(MoS_(2))owing to efficacious structural attributes and optimum hydrogen-binding free energy(ΔG_(H*))is emerging as a reliable alternative to PGMs.However,the performance of MoS_(2)-based electrocatalysts is still far away from the benchmark performance.The HER activity of MoS_(2)can be improved by engineering the structural parameters i.e.,doping,defects inducement,modulating the electronic structure,stabilizing the 1 T phase,creating nanocomposites,and altering the morphologies using appropriate fabrication pathways.Here,we have comprehensively reviewed the majority of the scientific endeavors published in recent years to uplift the HER activity of MoS_(2)-based electrocatalysts using different methods.Advancements in the major fabrication strategies including hydrothermal synthesis methods,chemical vapor deposition,exfoliation techniques,plasma treatments,chemical methodologies,etc.to tune the structural parameters and hence their ultimate influence on the electrocatalytic activity in acidic and/or alkaline media have been thoroughly discussed.This study can provide encyclopedic insights about the fabrication routes that have been pursued to improve the HER performance of MoS_(2)-based electrocatalysts.

Litchi-derived platinum groupmetal-free electrocatalysts for oxygen reduction reaction and hydrogen evolution reaction in alkalinemedia

Within the framework of the circular economy,the waste litchi’s skins were upgraded and transformed into electrocatalysts for oxygen reduction reaction(ORR)and hydrogen evolution reaction(HER).The waste litchi’s skins were pyrolyzed,activated,and then used as carbon support for fabricating metal–nitrogen–carbons(M–N–Cs)which belong to a promising class of platinum group metal-free electrocatalysts.The activated char was functionalized with transition metal(Fe,Ni,and Co)-phthalocyanine(Pc)in monometallic and bimetallic fashion by subjecting it to a thermal treatment at 600 and 900◦C.The samples functionalized at 900℃ showed higher performance for HER due to the formation of metal nanoparticles,whereas the samples functionalized at 600℃ showed higher performance for ORR.Particularly,sample Ni–Co 900 had an overpotential of−0.38 V for HER,while the sample Fe 600 was the most active electrocatalyst for ORR by demonstrating the onset potential of∼0.9 V(a half-wave potential of∼0.81 V)with the least production of unwanted peroxide anion.