Phase-engineered CoP-Co2P/coal-based carbon fibers composite as self-supporting electrocatalyst for efficient overall water splitting

The development of highly efficient electrocatalysts is critical to advancing overall water splitting (OWS). Herein, a self-supporting composite electrocatalyst based on CoP-Co 2 P/coal-based carbon fibers (CoP-Co 2 P/C-CFs) is successfully fabricated through phase-engineering. The formation mechanism of precursors is investigated, enabling precise modification of CoP and Co 2 P composite phases. This phase-engineering minimizes the Gibbs free energy of hydrogen adsorption, thereby enhancing OWS performance. In addition, the specific active sites involved in the OWS reaction are examined to confirm the effectiveness of phase modulation on CoP and Co 2 P. Furthermore, C-CFs derived from coal exhibit self-supporting properties as well as good acid and alkaline resistances, making them a promising potential candidate for OWS. A two-electrode cell assembled using CoP-Co 2 P/C-CFs exhibits a low voltage of 1.60 V at 10 mA cm −2 for OWS, superior to 1.64 V obtained using Pt/C//RuO 2 . This study not only presents a reliable strategy for obtaining phase-engineered cobalt phosphide catalysts but also outlines a novel approach for coal into high-value-added CFs. Consequently, it offers a new perspective for the development of self-supporting electrocatalysts for OWS.