A self-phosphorized carbon-based monolithic chainmail electrode for high-current-density and durable alkaline water splitting

Abstract

Developing cost-effective and efficient hydrogen/oxygen evolution reaction (HER/OER) electrocatalysts that can work stably at industrial-level current densities is of paramount importance for the scalable implementation of water electrolysis. Herein, a monolithic chainmail electrode is fabricated by embedding self-phosphorized graphitic carbon-encapsulated Co₂P nanoparticles within a hierarchically porous carbon membrane matrix (Co₂P@CTF) via the direct carbonization of a Co²⁺-cross-coupled soybean protein framework. While formulating the soybean protein framework into a hierarchically porous, mechanically strong, and conductive carbon membrane, the endogenous N and P sources enable the heteroatom doping of the carbon matrix while simultaneously yielding graphitic carbon-encapsulated Co₂P nanoparticles. Such an integrated Co₂P@CTF monolithic electrode exhibits remarkable alkaline water splitting performance with low overpotentials of 177.5 and 388.4 mV at 100 mA cm⁻² for the HER and OER, respectively, with excellent stability for the HER even at 1000 mA cm⁻² over 100 h and for the OER at 100 mA cm⁻² for >50 h. An electrolyzer assembled using Co₂P@CTF requires a cell voltage of 1.69 V at 10 mA cm⁻² with a high solar-to-hydrogen (STH) conversion efficiency of 16.8% when powered using a commercial silicon solar cell. This work opens a new avenue for scalable fabrication of monolithic chainmail electrodes with desirable functionalities for sustainable electrochemical energy conversion.