In-situ release of phosphorus combined with rapid surface reconstruction for Co–Ni bimetallic phosphides boosting efficient overall water splitting

Novel Co-Ni bimetallic phosphides with a 2D/3D structure were developed by in-situ phosphorization and rapid surface reconstruction strategies for use as an efficient electrocatalyst toward overall water splitting. In-situ phosphorus diffusion from the substrate was confirmed by high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) depth profiles. The generation of cobalt oxyhydroxide was also verified during electrochemical treatment, achieving surface self-reconstruction. The obtained materials revealed efficient and stable electrocatalytic performance, with HER and OER overpotentials of 117 mV and 272 mV, respectively. A low cell voltage of 1.59 V was achieved for overall water splitting with long-term stability. These properties were ascribed to the 2D/3D nanostructure with abundant interface defects. In-situ Raman spectroscopy and density functional theory (DFT) calculations were carried out to further understand the electrocatalytic activity and the promoted mechanism of reconstruction-derived CoOOH on OER performance.