Toward highly accessible Fe-N4 sites via rational design of metal chelated ionic liquids for ORR, OER and HER trifunctional electrocatalysis

The development of efficient non-precious, atomically dispersed single-atom catalysts (SACs) is vital for advancing fuel cell and water electrolyzer technologies. Here, we rationally designed a metal-chelated ionic liquid (M-IL) as a cornerstone (single source) to synthesize highly efficient M-SAC electrocatalysts via a robust and straightforward approach for ORR, OER, and HER reactions. The effect of temperature, as well as various metals (Fe, Co, Cu, Ni), on the formation of the M-SAC catalyst, was meticulously investigated. Among the designed single-atom catalysts, IL-Fe-SAC-8 delivered superior methanol tolerance toward ORR with a higher half-wave potential (0.90 V vs. RHE) and lower overpotential values of −0.127 V and 1.511 V vs. RHE, achieving a benchmark current density of 10 mA cm−2 toward HER and OER reactions. Thanks to the optimal graphitization, abundant defects, enhanced surface area, and high atomic coordination (supported by HAADF & XANES) of IL-Fe-SAC-8. Furthermore, the flexible DMFC assembled using IL-Fe-SAC-8 cathode delivered 2.5 times higher power density than the Pt/C-based cathode. When we tested a bifunctional IL-Fe-SAC-8||IL-Fe-SAC-8 electrolyzer, it achieved 1.58 V to deliver 10 mA cm−2. Moreover, for the real-time demonstration, we powered an H-type membrane water electrolyzer (separated by AEM) with a windmill and measured the hydrogen and oxygen produced concerning wind speeds. Furthermore, the produced hydrogen gas is used to power the lab-scale hydrogen fuel cell vehicle. This overall study demonstrates a new pathway to prepare unexplored atomically dispersed catalysts through a single source and template-free approach for next-generation energy technologies.