Zinc-air batteries (ZABs) are gaining attention due to their high energy density and potential for cost-effectiveness in energy storage applications. Recent advancements have focused on improving the performance of air cathodes, electrolytes, and zinc anodes. However, significant challenges remain, including the limited cycle life caused by zinc electrode degradation and dendrite formation, as well as the sluggish oxygen reduction and evolution reactions (ORR/OER) at air the cathode. Additionally, the instability of electrolytes hinders the commercialization of ZABs. Addressing these issues is critical for their future development and widespread adoption.
A cross-disciplinary and multinational effort led by IREC researchers has led to the publication entitled “Active site switching on high entropy phosphides as bifunctional oxygen electrocatalysts for rechargeable/robust Zn–air battery” in the journal Energy & Environmental Science from RSC. The researchers successfully report a new nanoscale FeCoNiPdWP high-entropy phosphide (HEP) particle as the air cathode, demonstrating promising bifunctional electrocatalytic performance in rechargeable ZABs. Meanwhile, the switching role of different metal active sites in high-entropy phosphides in oxygen redox reactions was clarified. This progress not only provides guidance for the design of bifunctional catalysts, but also paves the way for sustainable electric transportation and large-scale energy reserves of the future.
A deep understanding of the nature of active-site catalysis was key to this discovery. During the charge reaction for OER, the surface of the HEPs was reconstructed into a high-entropy oxyhydroxide, where Fe, Co, and Ni with high oxidation states served as the active sites, driving the reaction forward. Meanwhile, Pd and W played crucial roles in modulating the electronic structure, optimizing the adsorption energies of oxygen intermediates and ensuring efficient reaction kinetics. For the discharge reaction for ORR, Pd emerged as the primary active site, with strong d-d orbital coupling. In reconstrued HEPs, Pd, Co, and W fine-tuned electron transfer pathways and enhanced the catalytic efficiency. Each element performs its own function, maximizing the effectiveness of bifunctional catalysis, providing support for the high performance and long-term stability over 700 h of ZABs.
This research, led by Dr. Ren He, Dr. Linlin Yang and Prof. ICREA Andreu Cabot in Functional Nanomaterials Department atCatalonia Institute for Energy Research (IREC), was performed in collaboration with top scientists from Helmholtz-Zentrum Berlin für Materialien und Energie (HZB), National Centre for Nuclear Research (NCBJ), Institute of Science and Technology Austria (ISTA) and other prestigious international research institutions.
Find more details in the publication in Energy & Environmental Science: https://pubs.rsc.org/en/content/articlelanding/2024/ee/d4ee01912a
