Synthesis Of V-doped Nickel Nitride/nickel Heterostructure And The Applications In Hydrogen Electrocatalysis

The environmental issues caused by traditional fossil fuels burning have seriously affected the humanity’s living environment.As a clean energy with high energy density(147 kJ g-1),hydrogen has been considered as an ideal renewable energy substitute in the future.Water electrolysis and H2/O2 fuel cells can realize hydrogen production and utilization through hydrogen evolution reaction(HER)and hydrogen oxidation reaction(HOR),together establishing a sustainable hydrogen energy system.Due to the mild alkaline conditions,developing alkaline water electrolysis and H2/O2 fuel cells has gradually became the focus.Currently,Pt and its alloys still exhibit the highest activity towards HER/HOR,but the high cost and sluggish alkaline reaction kinetics greatly limit its large-scale industrial applications.Therefore,developing efficient and economical hydrogen electrocatalysts is significant to realize hydrogen economy.In this thesis,a novel Ni-based electrocatalyst was firstly designed and prepared,which exhibits remarkable alkaline HER/HOR performance.Density functional theory calculations further reveal the intrinsic activity of catalyst.Detailed research contents are given as follows:1.V-doped Ni3N/Ni heterostructure(V-Ni3N/Ni)grown on conductive carbon cloth was synthesized via a one-step hydrothermal and controlled nitridation method.Benefiting from the high-valence state V doping and heterostructure engineering,V-Ni3N/Ni exhibits excellent alkaline hydrogen electrocatalytic performance.In 1.0 M KOH electrolyte,V-Ni3N/Ni only requires 44 mV to reach the current density of 10 mA cm-2,exceeding most of Ni-based catalysts.Additionally,HOR test in 0.1 M KOH shows that V-Ni3N/Ni could reach a high current density of 1.54 mA cm-2 at 0.1 V(versus reversible hydrogen electrode),which is higher than Pt/C(1.47 mA cm-2).Moreover,V-Ni3N/Ni owns remarkable durability of 20 h in alkaline medium.When grown on nickel foam,the comparable activity of V-Ni3N/Ni to Pt/C further implies its intrinsic activity.2.Density functional theory calculations verify the electron transfers from Ni to Ni3N and V to nearby atoms(Ni,N)in V-Ni3N/Ni,respectively,which accordingly inducing asymmetric charge distribution.Additionally,V doping and heterojunction constructing synergistically regulate the water adsorption-dissociation ability and optimize the surface hydrogen adsorption Gibbs free energy(ΔGH*),further boosting the alkaline HER/HOR activity of V-Ni3N/Ni.