Ni-Regulated Self-Supported Mo-Based Electrodes for Hydrogen Production from High-Strength Livestock Wastewater

Developing highly active and stable self-supported electrodes is critical for efficient hydrogen production from high-strength livestock wastewater. Herein, self-supported NixMo1LDH-SP/NF electrodes (x = 1, 2, 3, and 4) were fabricated on nickel foam (NF) via a two-step hydrothermal process followed by sulfur/phosphorus (S/P) heat treatment. The effects of Ni precursor dosage on the electrode structure and hydrogen evolution reaction (HER) performance were systematically investigated. Varying the Ni dosage primarily modulated surface-layer assembly, while the electrodes exhibited similar Mo-based crystalline features across the series. Among the as-prepared electrodes, Ni2Mo1LDH-SP/NF exhibited the best HER performance in 1 M KOH, which was attributed to its radially assembled hierarchical rod architecture and abundant surface species that promoted electrolyte accessibility and active-site exposure. During electrolysis of high-strength livestock wastewater (OP3), Ni2Mo1LDH-SP/NF delivered lower cell voltages than NF in OP3-U, OP3-CF, and OP3-D, resulting in 18.4%, 17.4%, and 36.7% higher hydrogen production rates, respectively, while maintaining high hydrogen purity. Moreover, Ni2Mo1LDH-SP/NF consistently maintained higher hydrogen production rates than NF across varying concentrations of ammonia nitrogen (NH3-N), nitrate nitrogen (NO3−-N), total phosphorus (TP), and chemical oxygen demand (COD). Overall, the intermediate Ni/Mo precursor ratio enabled Ni2Mo1LDH-SP/NF to achieve a favorable balance between reaction kinetics, active-site accessibility, and interfacial mass transfer, highlighting its potential for hydrogen production from high-strength livestock wastewater.