Bi/BiFe(oxy)hydroxide for sustainable lattice oxygen-boosted electrocatalysis at a practical high current density

Lattice oxygen mechanism (LOM) is a promising pathway to circumvent sluggish oxygen evolution reaction (OER) for efficient water electrolysis. The iron (Fe)-based oxyhydroxide materials for OER catalysts by LOM is well known. However, dissolution of Fe atoms and promoting participation level of lattice oxygen at a practical and extremely high current density (> 1000 mA cm^-2 for oxygen generation) should be resolved for high performance and long-term stability. Here, controlling the reduction of synthetic intermediates allowed amorphous BiFe (oxy)hydroxides with secondary bismuth (Bi) metal (BM/BiFeO_xH_y) heterogeneous structures with abundant lattice vacancies to be obtained. The BM/BiFeO_xH_y electrode exhibited low overpotential of 232 and 359 mV at a current density of 10 and 1000 mA cm^-2, respectively. Moreover, the balanced hybridization of Bi/Fe-O was demonstrated to result in long-term catalytic stability without the dissolution of Fe atoms up to 1000 h at the extremely high current density of 1000 mA cm^-2 with negligible degradation. We further showed that the excellent performance of the newly proposed BM/BiFeO_xH_y electrocatalysts is attributed to the utilization of Fe/Bi-O hybridization, the induced amorphous structure, and increased lattice vacancies, which are systematically demonstrated by the electrochemical and physicochemical analysis and theoretical density functional theory (DFT) calculation.