Formic acid-assisted electrochemical deposition of CoMo-P on ZIF-67 derived NiCo LDH towards enhanced overall water splitting performance

Transition metal phosphides (TMPs) have emerged as promising candidates for the hydrogen evolution reaction (HER) due to their tunable phases and electronic structures. However, the development of bifunctional electrocatalysts that effectively balance HER and oxygen evolution reaction (OER) for overall water splitting presents a significant challenge. In this work, we report a novel cauliflower-like bimetallic phosphide, CoMo-P, synthesized on ZIF-67-derived NiCo layered double hydroxide (LDH) through a formic acid-assisted electrochemical phosphating process. This innovative approach not only enhances catalytic efficiency for both HER and OER but also offers a rapid, environmentally friendly, and straightforward fabrication method. The incorporation of formic acid during the electrodeposition process plays a crucial role in optimizing the catalyst's composition and microstructure. Specifically, formic acid facilitates the reduction rate of hypophosphite and stabilizes charged intermediates, thereby reducing the electrodeposition energy barrier and enhancing phosphating efficiency. As a result, the CoMo-P(NCL)/NF electrode demonstrates exceptional HER performance in alkaline media, achieving overpotentials of 55 mV and 108 mV at current densities of 10 and 50 mA cm ‑ 2 , respectively, significantly outperforming the control sample without formic acid addition (η 10 = 80.4 mV, η 50 = 142 mV). Moreover, the electrode exhibits remarkable OER activity with overpotentials of 273 mV and 310 mV at 10 and 50 mA cm ‑ 2 , respectively. When employed as a bifunctional catalyst for overall water splitting, the CoMo-P(NCL)/NF electrode pair requires a low cell voltage of 1.574 V to achieve a current density of 10 mA cm ‑ 2 , surpassing the performance of numerous reported bifunctional catalysts. This study provides a promising strategy for the rational design and practical application of high-performance bifunctional electrocatalysts in sustainable energy conversion systems.