Organic Upgrading through Photoelectrochemical Reactions: Toward Higher Profits

Aqueous photoelectrochemical (PEC) cells have long been considered a promising technology to convert solar energy into hydrogen. However, the solar-to-H-2 (STH) efficiency and cost-effectiveness of PEC water splitting are significantly limited by sluggish oxygen evolution reaction (OER) kinetics and the low economic value of the produced O-2, hindering the practical commercialization of PEC cells. Recently, organic upgrading PEC reactions, especially for alternative OERs, have received tremendous attention, which improves not only the STH efficiency but also the economic effectiveness of the overall reaction. In this review, PEC reaction fundamentals and reactant-product cost analysis of organic upgrading reactions are briefly reviewed, recent advances made in organic upgrading reactions, which are categorized by their reactant substrates, such as methanol, ethanol, glycol, glycerol, and complex hydrocarbons, are then summarized and discussed. Finally, the current status, further outlooks, and challenges toward industrial applications are discussed.