Electrocatalyst/Semiconductor Interfaces in Photoelectrocatalysts: Mechanistic Analysis of the Impact of Nanoparticle...

Interfaces between metal nanoparticle electrocatalysts (np-EC) and semiconductors (SC) play a key role in photovoltage generation in photoelectrochemical np-EC/SC water splitting systems. In this contribution, we investigate how the coverage of np-EC on SC influences the performance of photoelectrodes. We focus on a case study of np-Ni/n-Si photoelectrocatalysts for the oxygen evolution reaction (OER). By systematically varying Ni coverage, we show that np-EC coverage not only impacts light absorption and electrocatalytic activity but also governs the chemical evolution of the EC/SC interface under operating conditions by dictating the terminal thickness of interfacial insulating SiO_x layers that form during system operation. We demonstrate that this evolution of the interfacial SiO_x ultimately governs the system performance. We shed light on the underlying processes that govern the rate of growth for these interfacial oxide layers and describe how catalyst coverage impacts these processes. These findings highlight reaction environment-induced changes to the EC/SC interface as a critical parameter that affects the performance of photoelectrochemical systems.