Abstract

The development of self-standing bifunctional catalysts that are both durable and effective for the oxygen and hydrogen evolution reactions (OER/HER) is a critical step in advancing renewable energy sources for overall water splitting. Herein, self-standing nickel cobalt selenides were deposited on a macroporous conducting carbon electrode (NiCoSe<inf>2</inf>/MCE). A unique interconnected macropore MCE was derived from cigarette filters incorporated with activated carbon using the cryogel method. The resulting material underwent carbonization to produce conductive substrates with an improved surface area, structural integrity, and electrical conductivity. Subsequently, the MCE surface was coated with NiCoSe<inf>2</inf> via electrodeposition. By adjusting the deposition parameters and concentration of plating solutions, the electrocatalytic characteristics of NiCoSe<inf>2</inf> can be readily modified. The NiCoSe<inf>2</inf>/MCE catalyst exhibited remarkable HER performance, achieving a low overpotential of 162 mV at a current density of 10 mA cm⁻² and a Tafel slope of 53 mV dec⁻¹. For the OER, the catalyst exhibited a low overpotential of 290 mV at a current density of 10 mA cm⁻² and Tafel slope of 61 mV dec⁻¹. Furthermore, the NiCoSe<inf>2</inf>/MCE demonstrated exceptional durability for overall water splitting, maintaining 99 % of its initial current response after continuous operation for 24 h. Additionally, density functional theory calculations revealed that Se sites predominantly facilitated hydrogen adsorption due to their favorable Gibbs free energies, correlating closely with their distinctive 4d electronic states and significantly enhancing the observed catalytic activity. This study presents an effective approach for developing stable and functional electrocatalysts while offering insights into the utilization of low-cost materials.