Development of Se-doped Mn_0.5Cd_0.5S nanoparticles: an efficient dual-nature electrocatalysts for HER/OER in an alkaline electrolyte

Water electrolysis is a significant energy conversion strategy to generate sustainable and clean hydrogen and a practical approach to solving the world energy crisis. This technique demands eco-friendly, efficient, highly active catalysts for anodic and cathodic reactions, e.g., OER and HER. Transition metal sulfide-based catalysts have been widely explored as potential bifunctional electrocatalysts for water splitting. MnS-based catalysts are extensively attracted due to their diverse polyvalence nature, but, unfortunately, pure MnS-based catalysts have undesirable conductivity. We adopt heteroatom doping to accelerate the active site and improve conductivity. The Se-MnCdS nanoparticles-based electrocatalyst was synthesized on the stainless-steel substrate via the facile hydrothermal treatment. The chemical and physical techniques of the developed working electrode (Se-Mn_0.5Cd_0.5S) were ascertained through the XRD, IV, XPS, TEM, and EDX techniques. Therefore, Se doping in Mn_0.5Cd_0.5S effectively increases electrochemical performances and enhances electronic conductivity, as confirmed via experimental and systematic analysis. By optimizing the as-synthesized catalyst, the required over-potential for OER was only 276 mV, and for HER, 101 mV at benchmark current density (10 mAcm⁻²) in an alkaline medium. Also, low Tafel values for both reactions, such as for OER, 55 mVdec⁻¹, and 31 mVdec⁻¹ for HER, were observed. More than that, the Se-doped catalyst demonstrates long-term electrocatalytic stability during constant operation for 43 h for the OER and 34 h for HER in 1 M KOH solution. Consequently, our doping technique outcomes demonstrate the enhanced intrinsic and extrinsic electrocatalytic activity, and this work also allows a new avenue for synthesizing efficient dual-nature electrocatalysts for water electrolysis.