Rational design of septenary high-entropy alloy for direct ethanol fuel cells

Promoting C–C bond cleavage of ethanol by a complete 12-electron (12e) ethanol oxidation reaction (EOR) is a grand challenge for the development of highly efficient direct ethanol fuel cells (DEFCs). Most state-of-the-art catalysts only implement the EOR in an incomplete 4e or 2e pathway because of the poisoning of the catalysts by strongly adsorbed CO, leading to the poor output performance and low cell efficiency of DEFCs. Herein, a septenary PtPdFeCoNiSnMn high-entropy alloy (PtPd HEA) with a PtPd-rich surface but super-low platinum group metals loading was developed. We identified and proved the functions of each element in the PtPd HEA. The DEFCs assembled with the PtPd HEA (0.12 mgPtPd.cm−2) achieved a maximum power density of 0.72 W cm−2 and a durable operation for 1,200 h, which outperforms state-of-the-art catalysts for DEFCs. This work will be a design principle for nanostructured alloy development for renewable energy and sustainability applications. [Display omitted] •A septenary high-entropy alloy is developed for the direct ethanol fuel cell•The functional roles of each element in the PtPd HEA are identified•PtPd HEA exhibited a maximum power density of 0.72 W cm−2 for DEFCs•The DEFC assembled with PtPd HEA can be stably operated for 1,200 h Direct-ethanol-fuel-cell (DEFC) technology represents an effective and alternative method to obtain high power density with low carbon emissions. However, the complete ethanol oxidation reaction (EOR) at the anode side is still a big challenge due to the high activation-energy barrier to break the C–C bond. The oxygen reduction reaction (ORR) at the cathode side also faces slow reaction kinetics. Developing highly active and stable EOR and ORR catalysts with low-platinum-group-metal (PGM) content is urgent. In this work, a septenary PtPd HEA with a PtPd-rich surface was rationally designed. The PtPd HEA shows excellent activity and stability for the EOR and ORR respectively, which delivers a record-breaking performance with a maximum power density of 0.72 W cm−2 and steady operation for over 1,200 h for DEFCs. This work will establish a design principle for nanostructured alloy development for renewable energy and sustainability applications. A septenary PtPdFeCoNiSnMn high-entropy alloy (PtPd HEA) with a PtPd-rich surface was developed for the direct ethanol fuel cell. Pt and Pd are the active sites to catalyze the EOR, while the non-PGM elements can not only regulate the electronic structure of Pt and P