Photoelectrochemical water splitting: Materials design, deposition strategies, and efficiency limitations

Abstract

Photoelectrochemical (PEC) water splitting is a promising technology for producing clean hydrogen by directly converting sunlight into chemical energy. This review provides a comprehensive overview of the working principles, material requirements, and fabrication techniques that influence PEC performance, with particular emphasis on semiconductor photoelectrodes and thin-film coating methods. It discusses the key challenges associated with charge transport, reaction kinetics, and solar-to-hydrogen (STH) conversion efficiency. Common fabrication approaches, including hydrothermal synthesis, chemical vapor deposition, electrochemical deposition, sol-gel processing, spin coating, and spray pyrolysis, are critically compared in terms of photocurrent, cost, scalability, film quality, and reproducibility. Since photocurrent values reported in the literature are often measured under different experimental conditions, the review also evaluates standard performance metrics such as applied bias photon-to-current efficiency (ABPE), incident photon-to-current Efficiency (IPCE), Faradaic efficiency and STH efficiency. Recent advances in interface engineering, defect control and tandem PEC systems are highlighted. Although spin-coated photoelectrodes often deliver excellent performance, electrochemical deposition methods offer important advantages for large-scale and cost-effective photoelectrode fabrication. The review concludes by identifying key challenges and future research directions needed to achieve efficient, stable and commercially viable PEC hydrogen production.