Oxygen Plasma Triggered Co-O-Fe Motif in Prussian Blue Analogue for Efficient and Robust Alkaline Water Oxidation.

Abstract

In the context of oxygen evolution reaction (OER), the construction of high-valent transition metal sites to trigger the lattice oxygen oxidation mechanism is considered crucial for overcoming the performance limitations of traditional adsorbate evolution mechanism. However, the dynamic evolution of lattice oxygen during the reaction poses significant challenges for the stability of high-valent metal sites, particularly in high-current-density water-splitting systems. Here, we have successfully constructed Co-O-Fe catalytic active motifs in cobalt-iron Prussian blue analogs (CoFe-PBA) through oxygen plasma bombardment, effectively activating lattice oxygen reactivity while sustaining robust stability. Our spectroscopic and theoretical studies reveal that the Co-O-Fe bridged motifs enable a unique double-exchange interaction between Co and Fe atoms, promoting the formation of high-valent Co species as OER active centers while maintaining Fe in a low-valent state, preventing its dissolution. The resultant catalyst (CoFe-PBA-30) requires an overpotential of only 276 mV to achieve 1000 mA cm-2. Furthermore, the assembled alkaline exchange membrane electrolyzer using CoFe-PBA-30 as anode material achieves a high current density of 1 A cm-2 at 1.76 V and continuously operates for 250 hours with negligible degradation. This work provides significant insights for activating lattice oxygen redox without compromising structure stability in practical water electrolyzers.