Unveiling the surface hydroxylation and selenite modification of in situ generated nickel for promoting the hydrogen evolution reaction

Understanding the structural reconstruction of Ni-based materials under electro-reduction conditions and identifying the real active species in the alkaline hydrogen evolution reaction (HER) are significant for developing low-cost and efficient electrocatalysts. Moreover, the role of surface-adsorbed ions has not been fully elucidated after electrochemical reconstruction and severe leaching. Herein, taking (Ni-12(OH)(6)(SeO3)(8))(OH)(2) crystal as a pre-catalyst, multiple in situ and ex situ techniques verify that (Ni-12(OH)(6)(SeO3)(8))(OH)(2) is destroyed rapidly in the alkaline HER process and reconstructs into metallic Ni, followed by spontaneous surface hydroxylation, ultimately transforming into a Ni/Ni(OH)(2) heterostructure decorated with a small amount of selenite (SeO32-). The resulting material exhibits a low overpotential of 35 mV for HER at -10 mA cm(-2) in 1 M KOH and can be operated at -300 mA cm(-2) for 120 h without noticeable attenuation, outperforming most non-noble metal electrocatalysts. Theoretical calculations further prove that the surface-adsorbed SeO32- can regulate the electronic states of Ni sites, reduce the energy barrier of H2O-dissociation, and optimize the hydrogen adsorption free energy. These findings provide insight into the structural transformation mechanism and active species of electrode materials during the alkaline HER process.