Manipulating surface reconstruction and lattice oxygen mechanism of nickel (oxy)hydroxide by defect engineering for industrial electrocatalytic water oxidation

Heterogeneous doping is an effective strategy for enhancing oxygen evolution reaction (OER), but knowledge about the multielement synergistic effect remain largely unexplored and controversial due to surface complexity. Herein, we designed plain monometallic Ni(OH)2 with abundant oxygen and cation defects (D-Ni(OH)2) as research model to reveal OER promotion mechanism. Density functional theory calculation, in-situ Raman and various characteristic disclose that oxygen vacancies reduce the energy barrier for surface reconstruction to induce a higher degree conversion of active-phase NiOOH. Cation defects upshift the O-2p band center to enhance Ni-O covalency and activate lattice oxygen. Meanwhile, defects induced electron-rich environment prevent over-oxidation and dissolution of Ni ion to improve LOM's stability. The obtained D-Ni(OH)2 possesses exceptional OER activity with an overpotential of 217 mV at 10 mA cm- 2 and outstanding durability over 250 h at 1000 mA cm-2 in 1 M KOH, the assembled anion exchange membrane water electrolyzer (AEMWE) utilizing D-Ni(OH)2 as anode has low cell voltages of 1.45 V at 10 mA cm- 2 and maintain stability over 100 h at 1000 mA cm- 2, highlighting the crucial factor of determining OER kinetics and stability.