Structure and activity relationship in ACo2O4 (A=Fe, Mn, Ti) spinel oxides for alkaline HER in water splitting

Hydrogen production through water electrolysis is considered one of the most promising strategies for achieving sustainable, clean, and carbon-neutral energy generation. Herein, a series of spinel oxides, FeCo 2 O 4 , MnCo 2 O 4 , and TiCo 2 O 4 , were synthesized through the hydrothermal method followed by calcination. This research investigates the influence of Fe, Mn, and Ti on the cation distribution on the structural and electrocatalytic properties. X-ray analysis revealed the formation of a FeCo 2 O 4 /Fe 2 O 3 composite, while MnCo 2 O 4 resulted in a single-phase spinel, and TiCo 2 O 4 contained a minor TiO 2 impurity phase. Among the synthesized catalysts, FeCo 2 O 4 /Fe 2 O 3 exhibited improved HER activity, with an overpotential of 353 mV at 10 mA cm −2 and a Tafel slope of 73.2 mV dec −1 in an alkaline medium. The enhanced performance is attributed to low charge transfer resistance and increased electrochemically active surface area. These findings demonstrate that cation substitution is an effective strategy for tailoring the structural and electrocatalytic properties of spinel oxides for alkaline hydrogen production, contributing to SDG 7 and SDG 13 by the advancement of clean energy technologies and reduction of carbon emissions.