The Preparation Of Cobalt-based Nitride And Their Electrochemical Hydeogen Evolution Application

The rapidly increasing consumption of fossil fuels and associated environmental crisis have motivated pursue of alternative energy.Hydrogen has been commonly regarded as a key alternative to fossil fuels due to the merits of high energy density and zero pollutant emission.Among various hydrogen generation strategies,electrochemical hydrogen production powered by renewable electricity resources is considered as a promising and sustainable routine to large scale hydrogen production.However,the sluggish kinetics driven hydrogen evolution reaction(HER)and their associated substantial energy lost severely impedes the energetic efficiency of water splitting and boosts to explore efficient and robust HER electrocatalysts.The state-of-the-art HER electrocatalyst is Pt-based materials,of which the scalable application is seriously constrained by its scarcity and high cost.Accordingly,tremendous efforts have been devoted to develop inexpensive and earth-abundant non-noble metal electrocatalysts,such as transition mental phosphides(TMPs),sulfides,nitrides,carbides,to replace noble metal catalysts.Among them,cobalt-based compounds has been regarded as the potential HER catalyst due to the merits of earth-abundance and high catalytic activity.In this paper,cobalt-based compounds with the merits of earth-abundance and high catalytic activity was taken as the research object,aim to resolve the issue of limtted composition and undesired electronic structure of cobalt-based compounds and thus obtain HER catalyst with high activity via doping.On this base,combined with XPS,XANEs,UPS and DFT results,we extensively explore the modulation principle of doping on cobalt-based compounds and uncover the intrinsic factor that restrict the HER performance on molecule level.Our research provide guidance for construct high performance HER catalyst.The main research contents of this paper include following two aspects:Firstly,endowing materials with specific functions which are not readily available yet,is always of great importance but extremely challenging.Co4N with beneficial metallic characteristics has been proved highly active for water oxidation,while it is notoriously poor for hydrogen evolution reaction(HER)catalysis,due to its unfavourable d band energy level.Herein,we successfully endow Co4N with prominent HER catalytic capability,by tailoring the d band center positions via transition metal doping.The V doped Co4N nanosheets display an overpotential of 37 mV at 10 mA cm-2,which is substantially better than Co4N and even close to the benchmark Pt/C catalyst.XANES,UPS and DFT calculation consistently reveal the enhanced performance is attributed to the downshift of d band center,which help facilitate the desorption of adsorbed hydrogen.This concept could provide valuable insights into the design of other catalysts for HER and beyond.Secondly,transition mental phosphides have emerged as a promising catalyst for hydrogen evolution reaction.However,the HER performance of P-rich transition mental phosphides are not as excellent as predicted and the reason accounted for the inferior HER activity of P-rich phosphide on molecular-level is ambiguous.Herein,we first reported that the inferior HER performance of P-rich CoP2 is stemmed from the microenvironment differences of Pi and P2 atoms.Then,we develop a facile approach to improve the HER performance of CoP2 by incorporating N atoms.The as-obtained N-CoP2 drived 10 mA cm-2 at an overpotential of 37 mV,with superior long-term stability in acidic electrolyte.DFT calculations,XPS and XANEs results reveal that the superior activity of N-CoP2 is stemmed from the strong P-N interaction,which weaken the Co-P bonds,thus increase the density of active sites and optimize the Gibbs freeenergy of H absorption of P1 atoms.