Self-Supporting FeCoNiCuTiGa High-Entropy Alloy Electrodes for Alkaline Hydrogen and Oxygen Evolution Reactions: Experimental and Theoretical Insights

The preparation of clean and sustainable renewable energy requires the development of bifunctional electrocatalysts with high stability and activity for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Doping of Ga in the catalyst can enhance the catalytic reaction. In this study, we added different amounts of Ga to FeCoNiCuTi HEAs to make (FeCoNiCuTi)100–xGax (x = 1, 2, 3, 5, 10, 16.67) with a cost-effective HER/OER electrocatalyst that showed excellent electrocatalytic activity in the alkaline electrolyte. At a current density of 10 mA/cm2, it has an overpotential of 47 mV, a Tafel slope of 35.75 mV/dec, and an electric double-layer capacitance of 36.8 mF/cm2, which has excellent performance in the HER reaction. At the same current density, the overpotential of the OER is 345.56 mV, the Tafel slope is 33.9 mV/dec, and the electric double-layer capacitance is 31.24 mF/cm2, which is comparable to the overcapacitance of an inert catalyst. This makes it a highly efficient bifunctional electrocatalyst for alkaline integral water splitting. Density functional theory (DFT) calculations have shown that chemical complexity provides a strong synergistic effect for changing the electronic structure. The current work focuses on the possibility of adding Ga elements to high-entropy alloys for HER/OER.