Beyond Water Splitting: Developing Economic Friendly Photoelectrochemical Value-added Reactions for Green Solar-to-Chemical Energy Conversions

Facing climate change and the fossil fuel crisis, the global need for clean energy is more urgent than ever. Converting solar energy to produce green hydrogen fuel through photoelectrochemical (PEC) water splitting is a feasible strategy for utilizing solar energy, aligning with the increasing global demand for clean energy production. However, the energy conversion efficiency and overall economic benefit are severely limited by the slow kinetics of the oxygen evolution reaction (OER) and the low profitability of oxygen production, hindering the commercial utilization of PEC energy conversion technology. In the past few years, studies focusing on replacing the OER with PEC value-added reactions, which can produce high-value products, have received great attention. This not only improves the economic benefits of the general reaction system but also enhances the energy conversion efficiency. In this review, the basic principles of PEC value-added reactions and feedstock-product cost analysis are introduced first. Then, the latest research progress on PEC glycerol oxidation, H₂O₂ production, and ammonia splitting is summarized and discussed in detail. Finally, the status of commercial applications, further prospects, and challenges are discussed.