Optimization of catalyst loading on nickel foam substrates for monoclinic NaBiO2 towards OER applications

Recent decades have seen significant advancements in investigating binary metal oxides, especially regarding their use in electrocatalysis. Nonetheless, investigations into delafossite-type oxides (DOs), particularly Bi-based variations like NaBiO_2, are constrained by their complex nature, structural variety and formation issues. This work presents an innovative synthesis approach to producing monoclinic-phase NaBiO₂ by a straightforward and scalable co-precipitation technique. It emphasizes its applications as a remarkably stable and active electrocatalyst for the oxygen evolution reaction (OER). The key advancement is in the specific modification of catalyst loading to alter the material's surface characteristics, exhibiting electrochemically advantageous crystal characteristics. The optimized NaBiO₂ sample, produced under regulated loading circumstances, shows a distinctive flower-like petal shape, a large surface area and improved durability. Electrochemical investigation demonstrates exceptional OER activity, characterized by a low overpotential (η) of 243 mV, a minimal Tafel slope (35 mV/dec) and sustained stability exceeding 50 h at a 10 mA/cm² current density (C_d). The sample has an extraordinarily high electrochemically active surface area (ECSA) of 2022.25 cm² and an impressively minimal charge transfer resistance (R_ct) of 0.26 Ω. This study establishes a first comprehensive interaction between NaBiO₂ catalyst loading and OER efficiency, presenting a novel approach to optimizing delafossite-type oxides for energy-related applications. The results enhance the fundamental comprehension of Bi-based delafossite electrocatalysts and facilitate their widespread use in green energy conversion strategies.