Electrodeposition of FeCoNiCuMn high-entropy alloy nanoparticles as efficient bifunctional electrolytic water catalyst

Electrolyzed water can cope with the energy crisis very well, but the slow reaction velocity has severely hindered its development. So, it is imperative to establish an efficient, stable, and reserves-rich catalyst to accelerate the electrolysis of water. In this work, FeCoNiCuMn high-entropy alloy (HEA) particles around 5 nm in size are loaded on copper foam (CF) utilizing immediate current electrodeposition, which is applied to the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in potassium hydroxide solution. The loading of FeCoNiCuMn@CF HEAs is 19.8 mg cm−2, and the catalysts exhibit superior OER performance by electrochemical testing. It possesses a smaller overpotential (260 mV at 100 mA cm−2), a steeper Tafel slope (28 mV dec−1), and cycle stability of 30 h, which outperforms the catalytic activity of advanced precious metal catalyst RuO2. Meanwhile, the HER overpotential of FeCoNiCuMn@CF HEAs was -190 mV at a current density of 100 mA cm−2. These are primarily due to the increase in active sites generated by the size reduction and the lattice distortion of HEAs. This work shows that high catalytic activity relies not only on the changes of special surface but also on the intrinsic activity and structure of the catalyst. It offers new insight into the performance improvement of the catalysts in the electrolyzed water field.