Facile control of surface reconstruction with Co2+ or Co3+-rich (oxy)hydroxide surface on ZnCo phosphate for large-current-density hydrogen evolution in alkali

Abstract Surface reconstruction of transition metal based electrocatalysts is a highly efficient strategy for water splitting, which is usually observed in oxygen evolution reaction. However, most of them are not designed subjectively and it brings great difficulties to developing and understanding the catalysts with well-defined structure after the reconstruction. We demonstrate here the design and synthesis of ZnCo phosphate that allows a two-step treatment for controllable surface reconstruction with Co2+ or Co3+ (oxy)hydroxide. The surface reconstruction continuously boosts the HER performance in alkaline electrolytes. More aided experiments are designed to disclose that the depletion of PO43− in concentrated alkali and Zn2+ in following electrochemical etching serve as the key to trigger the reconstruction for Co2+-rich hydroxide and Co3+-rich oxyhydroxide, respectively. The reconstructed catalyst can work on hydrogen evolution for more than 50 h at high current density (1200 mA cm−2). Density functional theory simulations uncover the atomic-level understanding on the boosted catalytic performance. The energetically favorable electronic structure roots in the interfacial interaction and charge transfer. This work supplies valuable insights for the reconstruction chemistry and paves a new way to rational design heterogeneous catalysts associated with surface reconstruction in alkaline water electrolysers, and can cope with large-scale industrial water decomposition.