Boosting oxygen evolution reaction via Cl−-promoted electrochemical surface reconstruction in Prussian blue analogues

The oxygen evolution reaction (OER) is a vital half-reaction involved in water splitting applications. However, the slow kinetics of its four-electron transfer process have become a bottleneck for performance improvement. Surface engineering has emerged as a pivotal strategy to surmount the inherent kinetic limitations of OER. Herein, this work proposed a simple Cl − -promoted electrochemical surface reconstruction strategy. The as-obtained Ni 3 S 2 -PBA-NaCl-5000s exhibited excellent OER performance, with a low overpotential of 260 mV at 10 mA cm −2 and a small Tafel slope of 38.2 mV dec −1 in alkaline media. The addition of Cl − in the electrolyte not only accelerated the surface activation process but also modulated the structure of the in-situ generated NiFe oxide hydroxides/hydroxyls (NiFeOOH). Compared to the pure KOH condition, the obtained NiFeOOH exhibited a larger surface area, yielded a higher concentration of OH − environment on the surface, which facilitated the OER kinetics rate. Moreover, lattice oxygen is triggered, thus enabling the reaction via a faster lattice oxygen-mediated mechanism (LOM) pathway, which presents lower thermodynamic barriers. This work may offer a fresh perspective on clarifying the OER activity enhancement mechanism by the influence of Cl − in the electrolyte on the electrochemical surface reconstruction process.