High Performance and Surface Stability of Fe-Bi Heteroanionic Compounds for Electrocatalytic Oxygen Evolution Reaction

<br/>Successful utilization of hydrogen (H₂) production and storage technology from water medium depends on exploring novel catalyst materials for oxygen evolution reaction (OER). Especially, low oxygen (O₂) generation activity and stability of OER catalyst materials are the major bottlenecks for overall water-splitting efficiency. Recently, continued improvements in OER electrodes mainly rely on the choice of a wide variety of transition metal-based materials and the judicious control of surface properties by replacing surface functional groups, constructing nano-architectures, and doping active atom species. Among them, the large family of transition metal (TM) heteroanionic compounds are widely regarded as a promising electrode candidate for OER due to its high catalytic activities and unique OER mechanism. Compared to the conventional adsorbed evolution mechanism (AEM) for OER, recently identified particular TM-heteroanionic materials can efficiently produce O₂ compounds by direct O-O coupling between incorporated lattice oxygen on the surface of materials and electrolyte ions (lattice oxygen mechanism, LOM). However, due to its lattice-involved mechanism, the OER stability of TM-heteroanionic materials is not well studied. Moreover, TM-heteroanionic materials lack OER catalytic endurance for long-term operation at high current level while LOM paths. One way to improve the stability of those TM-heteroanionic materials is to control the level of TM-O hybridization conditions to facilitate the adsorption and interaction of electrolyte ions within LOM intermediates. Therefore, finding new TM material candidates that effectively sustain the initial structure and lattice active sites of LOM is highly required. Herein, we firstly propose iron (Fe)-incorporated bismuth (Fe/Bi) heteroanionic compounds for OER catalysts. Due to its unique structure and electronic hybridization level of Fe/Bi-O, the OER electrodes exhibit a relatively low overpotential of ~ 250 mV at a current density of 10 mA cm^-2 with a low Tafel slope of ~ 35 mV dec^–1. Along with its enhanced OER performance, the Fe/Bi heteroanionic electrodes show the superior cycling stability, and the stability performance is well-maintained after 10 hr operating at an extremely high current density of 1000 mA cm^-2. The newly proposed Fe-Bi heteroanionic materials and introduced amorphous structures can guarantee the high OER activity by the dually-induced LOM mechanism and the high electrochemical stability of the electrode materials by the optimized TM-O hybridization by the existence of Fe and Bi atoms. These findings demonstrate that this novel Fe-Bi heteroanionic compounds can be used to provide promising electrochemical performance in terms of both OER activity and stability for future energy generation/storage applications.