Optimizing the nickel/cobalt stoichiometry in selenide for enhanced electrocatalytic hydrogen evolution over a wide pH range

Abstract

The development of universal electrocatalysts for the hydrogen evolution reaction (HER) across a wide pH range holds significant promise for energy applications, but it remains a substantial challenge. Herein, density functional theory (DFT) calculations were initially conducted to pre-analyze the feasibility of bimetallic nickel cobalt selenide for HER. Guided by the DFT calculations, we propose a practicable strategy for enhancing the activity of bimetallic selenide through optimizing the stoichiometric ratio of nickel and cobalt, with NiCo PBA serving as a precursor. XRD and ICP-OES analyses revealed that Ni_0.629Co_0.371Se₂, Ni_0.631Co_0.369Se₂, and Ni_0.641Co_0.359Se₂ were successfully synthesized and utilized as HER catalysts over a wide pH range. Consequently, Ni_0.631Co_0.369Se₂ requires only 155, 168, and 294 mV to reach 10 mA cm⁻² in alkaline, acidic, and neutral media, respectively, significantly outperforming Ni_0.641Co_0.359Se₂ (166, 185, and 319 mV) and Ni_0.629Co_0.371Se₂ (227, 220, and 372 mV). The enhanced HER activity can be attributed to the optimization of the nickel/cobalt stoichiometric ratio. This study provides a viable approach for the design of advanced bimetallic selenide electrocatalysts for the HER.