Synthesis Of Nickel/Cobalt-Based Array Catalysts And Its Nitrogen-Doping Modification For Electrocataivsis

Oxygen evolution reaction,as a necessary process in water splitting,depends on the advancement of cost-effective efficient electrocatalysts.Currently,noble metal oxides set the benchmark for OER electrocatalysts.However,the scarcity,prohibitive cost,and poor long-term durability of these materials restrict their wide application.It is widely recognized that materials based on the transition metal composites are promising alternatives due to their reasonable cost,natural abundance,high conductivity,and outstanding stability.But the bulk materials and powders still suffer from the limited surface area and poor conductivity thus unsatisfied electrocatalytic activity.Herein,with the help of nitrogen-doping strategy,combining with nanostructure design,we reported N-doped materials as advanced and efficient electrocatalysts.The main contents and results are as follows.（1）We have constructed N-CoO nanowire arrays as efficient electrocatalysts towards OER in alkaline solution via a facile hydrothermal method.The as-prepared N-CoO nanowire arrays possess open framework and porous nanostructure,demonstrating increased accessible contact and active areas and rich/short pathways for electron/ion transfer.Hence,the N-CoO electrode shows excellent electrocatalytic performance for OER with a low overpotential and a low Tafel slope of 74 mV dec^-1 as well as superior long-term durability for 24 h in 1 M KOH solution.（2）We have demonstrated the 3D cross-linked porous nickel arrays as robust high-efficiency electrocatalysts via a versatile one-step electrodeposition method.The rational design for interconnected highly porous construction allows larger active surface area,richer transport channels for electron/ion transfer as well as improved electron conductivity,leading to superior electrochemical performance.The nickel arrays are firmly composited with the Ni substrate ensuring good mechanical stability and long-term stability.（3）We have rationally designed and fabricated N-doped sponge nickel as a novel and efficient OER electrocatalyst.The new material exhibits a 3D porous sponge skeleton with increased accessible surface area.The N-SN electrode shows high conductivity and abundant active sites,which result in excellent electrocatalytic performance,with low overpotential and high cycling stability.XPS and NEXAFS measurements were used to study the OER mechanism of N-SN;γ-NiOOH,originating from the oxidation of N-SN in alkaline solution,is identified as the actual active material for OER.In this work,we have not only demonstrated the potential of N-SN as a novel electrocatalyst,but also provided insights into designing advanced transition-metal-based electrocatalysts for OER.