Refining Mn–Ni synergy for the design of efficient catalysts in electrochemical ethanol oxidation

Abstract

Developing catalysts based on non-precious metals is crucial for the electrochemical oxidation of ethanol, a pivotal anodic reaction in direct ethanol fuel cells. In this study, we crafted a series of Mn oxyhydroxides/Ni catalysts via a straightforward electrochemical deposition of Mn onto Ni foam. By carefully modulating the concentration of Mn²⁺ during electrodeposition, we achieved a tunable surface Mn/Ni ratio and Mn–Ni synergy. It is observed that with increasing Mn/Ni ratio, the electrochemically active surface area (ECSA) increases monotonously, while the intrinsic activity increased first and then decreased. Consequently, electrodes with surface ratios of 6.1 and 8.6 exhibit relatively lower intrinsic activity but higher ECSA, ultimately attaining the highest apparent activity (94–98 mA cm⁻² peak current density at 1.50 V vs. reversible hydrogen electrode) for ethanol oxidation. This work provides an accessible approach to tailor Mn–Ni synergy, paving the way for the design of highly efficient catalysts for electrochemical ethanol oxidation.