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

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 the alkaline electrolyte with urea, Fe2GeO4, which was used as the anode in the electrolysis cell, exhibited lower potential (1.53 V (vs. RHE)) and smaller Tafel slope (76 mV/dec) than that of the Co2GeO4 (1.65 V (vs. RHE), 79 mV/dec), 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 these of the Co2GeO4. Hence, Fe2GeO4 showed 5.49 times higher H2 peak intensity than that of Co2GeO4, indicating higher efficiency of H2 production.