Total Water Splitting Catalyzed by Co@Ir Core–Shell Nanoparticles Encapsulated in Nitrogen-Doped Porous Carbon Derived from Metal–Organic Frameworks

Developing bifunctional electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) toward overall water splitting with high efficiency and robust durability is highly desirable but very challenging. Herein, we report a highly efficient and robust bifunctional electrocatalyst for overall water splitting based on Co@Ir core–shell nanoparticles encapsulated in nitrogen-doped porous carbon derived from metal–organic frameworks. The series of Co@Ir/NC- x samples were prepared through a galvanic replacement of IrCl 3 with Co/NC, which was obtained by calcination of zeolitic imidazolate framework 67 (ZIF-67). In the electrocatalytic characterizations toward OER and HER, Co@Ir/NC-10% exhibited the best performance among the series, with an overpotential of 280 mV at a current density of 10 mA cm –2 for OER, superior to the benchmark IrO 2 catalyst, and an overpotential of −121 mV at a current density of 10 mA cm –2 for HER in 1 M KOH. Moreover, Co@Ir/NC-10% also demonstrated markedly higher long-term stability than IrO 2 for OER and superior long-term durability than Pt/C for HER. Finally, the overall water splitting catalyzed by the series of composites was explored and visually observed.