Tailoring Cu-based nanostructures via sulfur doping and precursor selection for efficient bifunctional water splitting electrocatalysis

The development of efficient and robust electrocatalysts for water splitting is crucial for advancing sustainable hydrogen production. In this study, we systematically investigate the influence of copper precursor selection and sulfur doping on the structural, electronic, and electrocatalytic properties of copper phosphide-based nanostructures. Nanostructured Cu₃P, CuS, and S-doped Cu₃P were synthesized using either CuCl₂ or Cu(OAc)₂ as copper sources. Comprehensive structural and surface analyses reveal that precursor choice significantly affects particle size, morphology, and surface composition, with CuCl₂ favoring the formation of larger, well-defined crystals, and a higher surface Cu(I) content. Sulfur incorporation induces lattice contraction and electronic modulation, which further enhances the intrinsic activity and surface oxophilicity. The best-performing catalyst, S-doped Cu₃P synthesized from CuCl₂ (S-Cu₃P-C), demonstrates impressive bifunctional activity in 1 M KOH, reaching 10 mA cm⁻² at 265 mV overpotential for HER (Tafel slope of 107 mV dec⁻¹), and achieving 300 mV overpotential for OER with a Tafel slope of 140 mV dec⁻¹. Post-catalysis XPS analysis confirms that these catalysts retain more active surface states and undergo less detrimental oxidation. These findings underscore the synergistic roles of precursor chemistry and sulfur doping in tailoring the structure and activity of copper-based electrocatalysts, providing valuable insights for the rational design of advanced materials for efficient water splitting.