Boosting sustainable hydrogen production via water splitting and urea oxidation using spinel hollow-sphere nano catalysts

In this study, spinel MgCo₂O₄ materials were synthesized using three different techniques: freeze-drying, solid-state, and hydrothermal methods, to evaluate their structural, morphological, and electrocatalytic properties. Comprehensive characterization techniques including XRD, Raman spectroscopy, FT-IR, FESEM, HRTEM, and XPS confirmed the successful formation of phase-pure MgCo₂O₄ with varied morphologies. Among the synthesized materials, the freeze-dried sample exhibited a well-defined hollow-sphere structure, providing abundant electroactive sites and superior electron/mass transport pathways. This morphology contributed to outstanding electrocatalytic performance. For the oxygen evolution reaction (OER), the hollow-sphere MgCo₂O₄ catalyst demonstrated a low overpotential of 430 mV at 10 mA cm⁻² and a Tafel slope of 190 mV dec⁻¹. In addition, the same catalyst exhibited excellent activity for the urea oxidation reaction (UOR), with a Tafel slope of 95 mV dec⁻¹ and enhanced current density under alkaline conditions. The superior UOR activity, enabled by the lower oxidation potential of urea (∼0.37 V vs. RHE), also highlights its potential for energy-efficient hydrogen production and wastewater treatment. This work establishes a scalable and cost-effective strategy to synthesize high-performance MgCo₂O₄ hollow-sphere electrocatalysts, paving the way for their application in sustainable energy and environmental technologies.