Reconstruction of Ni-Co Phosphites Precatalyst into Metal Oxyhydroxides for Durable Full Water Electrolyzer Cell

Developing cost-effective and catalytically high active noble-metal-free electrocatalysts is of great importance for high-performance and long-durable water electrolysis systems. Herein, nickel-cobalt phosphite (NCP) (M₁₁(HPO₃)₈(OH)₆, M = Ni and Co) microbuds are directly deposited on nickel foam (NF) by a one-step hydrothermal method to serve as an electrocatalyst for oxygen evolution reaction (OER). Owing to high electrochemical activity and good electrokinetics, the NCP material prepared for 5 h of reaction time (NCP-5 h@NF) as the precatalyst demonstrated superior OER activity with an overpotential of only 246 mV to generate a current density of 10 mA cm^-2. It also exhibited a lower Tafel slope of 77 mV dec^-1. In addition, the NCP-5 h@NF revealed a stable OER activity over 24 h of the chronopotentiometry test. Concurrently, the catalyst surface was reconstructed by transforming its surface into microflowers. Moreover, an anion-exchange membrane water electrolyzer cell (AEMWEC) was fabricated with NCP-5 h@NF as an anode and platinum-carbon as a cathode to explore the capability of the NCP catalyst in an overall water splitting. The AEMWEC not only delivered a high electrolysis performance of 824 mA cm^-2at ∼2 V but also conserved its catalytic activity for 240 h. This new approach promotes the fabrication of cost-effective and noble-metal-free catalysts by one-step methods for durable water electrolysis systems.