Deciphering the Synergistic Effect in Strong Metal–Support Interaction toward Surface Reconstruction of Prussian Blue Analogue-Based Pre-Catalysts for Boosted Bifunctional Oxygen Electrocatalysis via Operando Raman Spectroscopy

The strong metal–support interaction (SMSI) effect in Prussian blue analogues (PBAs) has been widely investigated and is credited for the enhanced activity, selectivity, and durability for electrocatalysis reactions. However, deciphering the contribution of individual components and identifying the active sites in PBA-based pre-catalysts for electrocatalysts are seldom realized. Herein, we report the unraveling of the synergism in a cobalt hexacyanoferrate (CoHCF) PBA pre-catalyst-decorated three-dimensional (3D) network of interlinked graphene oxide and functionalized carbon nanotubes (GO/f-CNT) for the boosted bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). We find that the SMSI between CoHCF and GO/f-CNT modulates the surface reconstruction of the PBA pre-catalyst for boosted activity and durability. Besides, the SMSI effect leads to a change in the rate-determining step (RDS) from surface-adsorption-limited over CoHCF to charge-transfer-controlled over CoHCF/GO/f-CNT during the ORR. Operando Raman spectroscopy confirms this finding and demonstrates the lowered overpotential for the ORR over GO/f-CNT predominantly due to efficient adsorption of O 2 – (an ORR intermediate), while CoHCF provides a 4-electron ORR pathway. In the OER, the leaching of Fe­(CN)6 species from the CoHCF pre-catalyst under alkaline conditions generates OER-active CoOOH/FeOOH on the surface.