Boosting eco-friendly hydrogen generation by urea-assisted water electrolysis using spinel M2GeO4 (M = Fe, Co) as an active electrocatalyst

Abstract

To enhance the efficiency of hydrogen production, bimetallic oxides with spinel structures, M₂GeO₄ (M = Fe, Co), were synthesized via a facile one-pot hydrothermal method and were used as electrocatalysts for urea-assisted water electrolysis. In alkaline electrolyte with urea, Fe₂GeO₄, which was used as the anode in the electrolysis cell, exhibited a lower potential (1.53 V (vs. RHE)) and a smaller Tafel slope (76 mV dec⁻¹) Co₂GeO₄ (1.65 V (vs. RHE), 79 mV dec⁻¹), indicating that Fe₂GeO₄ reduced the overall input potential to produce H₂. The superior performance of Fe₂GeO₄ in the urea-added water electrolysis was attributed to the higher oxidation state of its metal cations, larger electrochemical active surface area, and lower charge transfer resistance than those of Co₂GeO₄. Hence, Fe₂GeO₄ showed 5.49 times higher H₂ peak intensity than Co₂GeO₄, indicating higher efficiency of H₂ production.