Strategies for improving Co/Ni-based bimetal-organic framework to water splitting

Abstract The preparation of high-efficiency, stable, and low-cost oxygen evolution reactions (OER) and hydrogen evolution reactions (HER) electrocatalysts remains a challenge for new energy systems. In this study, three-dimensional (3D) cobalt-nickel bimetal MOFs were used as precursors to synthesize catalysts through thermal decomposition, carbonization, nitriding, oxidation, phosphating, sulfurizing, and selenization, respectively. In 1.0 M KOH electrolyte, the overpotential of Co/Ni-MOFs@Se for OER was 238 mV and the that of Co/Ni-MOFs@P for HER was 194 mV at a current density of 10 mA cm−2. Based on the excellent OER and HER performances of Co/Ni-MOFs@Se and Co/Ni-MOFs@P, these two materials were further assembled into electrodes for overall water splitting. Results showed that a potential of only 1.59 V was required to provide a current density of 10 mA cm−2. The electrodes also exhibited long-term durability in a 2000 min stability test without significant changes in the catalytic performances. According to the difference in the doped non-metal elements, an electrode pair with a suitable matching degree was constructed, thereby improving the overall water splitting performance. Thus, the controllable modification of the metal-organic frameworks (MOFs)-derived carbon materials (CMs) effectively improved the materials’ catalytic water splitting performance. It was possible to further develop an efficient, inexpensive, and low-cost assembled electrode pair.