Preparation and Electrocatalytic Hydrogen Evolution Performance of FeCoNiCrMo High-Entropy Alloy Porous Electrode with Different Pore-Forming Agent Content

The electrocatalytic hydrogen evolution performance of FeCoNiCrMo high-entropy alloy (HEA) coating with different porosity prepared by plasma spray was investigated in this study. The feedstock powder is prepared by atomization method and mechanically mixed with an additional content of Al powder. The plasma spray prepares the mixture coatings on the Cu substrate. The porous electrocatalytic electrodes are obtained by the dealloying method. The porous HEA electrodes present the major FCC phase, the phase FeCrNiMo, and the phase Al 2 O 3 , wherein the Al 2 O 3 formed due to the residual of the Al element. The oxides on the surface composed of Fe 2 O 3 , FeO, Co 2 O 3 , CoO, NiO, Ni 2 O 3 , Cr 2 O 3 , MoO 2 , and MoO 3 . Adding Al content increases the porosity, approaching 13.19%, 29.68%, and 47.34%. The pores are fine and dispersed in the 30 vol.% Al HEA coating, expected to present high performance. The electrochemical tests revealed that the 30 vol.% Al HEA coating presents the lowest overpotential, − 0.174 V, and the lowest charge transfer resistance, 61.91Ω, corresponding to the highest HER electrocatalytic activity. In addition, after 1000 and 2000 cycles of the CV test, the overpotential is still − 0.181 and − 0.19 V, respectively, which indicates the porous HEA coating exhibits outstanding stability. To sum up, the FeCoNiCrMo HEA system shows a potential for electrocatalyzing HER. Meanwhile, the plasma spray followed by dealloying is a feasible method to prepare the porous catalytic electrode with a high performance. This study will provide a new idea for organizing and designing catalytic electrodes.