In situ construction of hybrid Co(OH)2 nanowires for promoting long-term water splitting

Engineering the interfacial structure of hybrid catalysts is crucial for enhanced electrocatalytic performances. Herein, a new strongly heterogeneous catalyst of Co/CoO/Co(OH)2 nanowires with proper interfacial structure was synthesized via a plasma etching approach. X-ray photoelectron spectroscopy and electron energy loss spectroscopy revealed that strong chemical couplings at the hybrid interface induced fast charge transfer, leading to considerable amounts of Co2+/Co sites present in the hybrid. The high conductivity from metal Co and one dimensional nanostructure favored the electron transfer and electrolyte access. The metallic Co was further oxidized to Co2+/Co3+ to address instability under applied potential during long-term testing. The resulting catalyst exhibited an excellent overpotential of 266 mV at 20 mA cm−2 and a Tafel slope of 85 mV dec−1 in alkaline medium. Importantly, the hybrid Co/CoO/Co(OH)2 demonstrated a super long-term durability over 200 h among the most ultra-long stability Co-based OEC catalysts. This catalyst was applied on light absorbing BiVO4 for solar-driven water splitting, exhibiting a significantly enhanced photoelectrochemical (PEC) activity, 5.32 mA cm−2 obtained at 1.23 VRHE, which represented one of the best performances achieved by Co-based OER cocatalysts.