NiCoP@CoNi-LDH/SSM as a multifunctional catalyst for high-efficiency water splitting and ultra-long-life rechargeable zinc-air batteries

Abstract

The design and development of self-supporting multifunctional catalysts for efficient water splitting and long-life rechargeable zinc-air batteries (ZABs) is of great significance for energy conversion. Different from previously reported metal layered double hydroxides (LDHs) grown on metal phosphides, herein, we synthesize a CoNi-LDH precursor with a larger exposed surface area on a stainless-steel mesh (SSM), followed by direct surface phosphating to form NiCoP@CoNi-LDH. The obtained NiCoP@CoNi-LDH/SSM demonstrated enhanced HER, OER and ORR properties compared to the CoNi-LDH/SSM precursor, and comparable to or even superior to those of commercial catalysts. Moreover, when applied as the air-cathode of a ZAB, it can continue to operate for a long lifetime of more than 1500 h during charge and recharge testing at a current density of 10 mA cm⁻², with a low voltage gap of only 0.81 V before 900 h. Additionally, the assembled ZAB can efficiently drive a two-electrode water-splitting experiment. The acquired voltage is only 1.579 V when the output current density is 10 mA cm⁻², which is much lower than that of the CoNi-LDH/SSM precursor (1.719 V), or even the commercial Pt/C/SSM∥RuO₂/SSM (1.626 V) electrode pair. After deeply analyzing the insight into the influence of the surface phosphating, we confirmed that both the generated NiCoP@CoNi-LDH heterojunction and the formed NiCoP nanoneedle enhanced the inherent multifunctional properties of NiCoP@CoNi-LDH/SSM. This work provides a superior trifunctional catalyst, and we believe that it will advance a novel idea for the design of efficient multifunctional nanomaterials.