Role of transition-metal electrocatalysts for oxygen evolution with Si-based photoanodes

Abstract A comprehensive understanding of the role of the electrocatalyst in photoelectrochemical (PEC) water splitting is central to improving its performance. Herein, taking the Si-based photoanodes (n+p-Si/SiOx/Fe/FeOx/MOOH, M = Fe, Co, Ni) as a model system, we investigate the effect of the transition-metal electrocatalysts on the oxygen evolution reaction (OER). Among the photoanodes with the three different electrocatalysts, the best OER activity, with a low-onset potential of ∼1.01 VRHE, a high photocurrent density of 24.10 mA cm−2 at 1.23 VRHE, and a remarkable saturation photocurrent density of 38.82 mA cm−2, was obtained with the NiOOH overlayer under AM 1.5G simulated sunlight (100 mW cm−2) in 1 M KOH electrolyte. The optimal interfacial engineering for electrocatalysts plays a key role for achieving high performance because it promotes interfacial charge transport, provides a larger number of surface active sites, and results in higher OER activity, compared to other electrocatalysts. This study provides insights into how electrocatalysts function in water-splitting devices to guide future studies of solar energy conversion.