Strategic design of cellulose nanofibers@zeolitic imidazolate frameworks derived mesoporous carbon-supported nanoscale CoFe2O4/CoFe hybrid composition as trifunctional electrocatalyst for Zn-air battery and self-powered overall water-splitting

A novel “Nucleation growth & Spatial isolation” strategy is reported to construct the high-efficient multifunctional electrocatalyst via pyrolysis of the cellulose nanofibers (CNFs) coating with Fe embedded bimetal-zeolitic imidazolate frameworks (ZIFs) of ZIF-67/ZIF-8. Taking advantages of strategically structural design effectively inhibits Fe/Co metal species migration and agglomeration during the pyrolysis process, deriving the nanoscale-dispersed CoFe2O4/CoFe active sites and abundant mesoporous structure which ensures more effective exposure in the optimized FeZn4Co@CNFs sample. With a half-wave potential E1/2 of 0.84 V for oxygen reduction reaction (ORR), small overpotential 0.36 V and 0.20 V for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively, FeZn4Co@CNFs presents the one of most Fe/Co-based trifunctional electrocatalysts reported to date, also is comparable to the benchmark Pt/C and RuO2 catalysts. Furthermore, a rechargeable FeZn4Co@CNFs-based Zn-air battery endows a high power density of 107.6 mW cm−2 and an outstanding cycling stability. Remarkably, the overall water-splitting is successfully driven by FeZn4Co@CNFs-based Zn-air batteries for generating H2 and O2 bubbles. Our finding provides a new guidance to strategic design and develop nanoscale-dispersed active sites in non-noble metal trifunctional electrocatalysts.