Tuning the d-Band Center in Prussian Blue Analogues via Modulated Carbon and Nitrogen Coordinated Metals for Boosted Bi-Functional Oxygen Electrocatalytic Activity

The d-band center is a promising descriptor to understand trends in electrocatalysis extensively studied in transition metal oxides but largely unexplored in metal organic frameworks (MOFs). Herein, we present our systematic study aimed at developing a mini-volcano plot demonstrating dependence of bifunctional oxygen electrocatalytic activity of Prussian blue analogues (PBAs) on their d-band center. Our results from ex-situ core level and valence band XPS, Raman, and FTIR spectroscopy suggest that the tuning of the d-band center via modulated N and C-coordinated metal centers dictates their electrocatalytic OER and ORR activities. Among PBAs, the CoCo PBA exhibits highest activity due to its optimal position of d-band center and abundant Co³⁺ active sites. Moreover, M-Co PBAs showcased superior performance compared to M-Fe PBAs, attributed to facile formation of surface-active sites, i.e., metal oxy(hydroxide). The study advances the understanding of the influence of metal center tuning in PBAs on the intermediate energies and catalytic activity.