Electronic Regulation by Fe-Doped CoPx Hydrophilic Self-Supported Nanorod Arrays as Bifunctional Electrocatalysts for Superior Overall Seawater Splitting

Abstract

To address the challenge of designing a highly reactive and stable bifunctional electrocatalyst for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), a hydrophilic Fe-CoP_x nanorod array on nickel foam (NF) was designed and prepared in this work. The modulation of a d-band center of Co by adding Fe effectively optimized the adsorption energy of intermediates. The synergistic effect of the bimetallic active sites significantly enhanced the electrocatalytic performance for both reactions. In alkaline seawater, Fe-CoP_x/NF exhibited excellent HER (−32 mV at −10 mA cm^–2) and OER (216 mV at 10 mA cm^–2) activities, maintaining stability for over 100 h at 100 mA cm^–2. For overall seawater electrolysis, the catalyst achieved a low cell voltage of 1.54 V at 10 mA cm^–2, outperforming the conventional RuO₂∥Pt/C electrode (1.58 V at 10 mA cm^–2). Additionally, in a simulated industrial flow cell, the catalyst operated stably for over 200 h at 100 mA cm^–2, indicating its strong potential for practical applications. This study introduced a simple synthesis method for bimetallic phosphides, providing a new avenue for the design of high-performance bifunctional catalysts for seawater electrolysis.