Alternatives to Water Photooxidation for Photoelectrochemical Solar Energy Conversion and Green H_2 Production

摘要

Photoelectrochemical (PEC) water splitting is considered a promisingtechnology to produce renewable hydrogen, a clean fuel or energy carrierto replace conventional carbon-based fossil-fuel sources. Nevertheless,the overall solar-to-hydrogen efficiency and the cost-effectiveness of thistechnology are still unsatisfactory for practical implementation. This can beprimarily attributed to the sluggish kinetics of the anodic oxygen evolutionreaction (OER) and the relatively low economic value of cogenerated O_2 production.Over the past decades, there are extensive efforts to explore morekinetically favorable photooxidation reactions, which coupled with hydrogenevolution reaction (HER) can simultaneously improve H_2 production yieldand produce higher valuable alternatives to conventional O_2. This reviewaims to present recent progress on the alternative anodic choices to OER.Here, the fundamental of PEC water splitting and the critical componentsrequired for this system are first shortly summarized. Then the benefits andissues of alternative photooxidation reactions including photooxidation ofwater to hydrogen peroxide, chlorine, alcohol, 5-hydroxymethylfurfural, orurea oxidation when combined with the concurrent HER, are reviewed andanalyzed. This review is concluded by presenting a critical evaluation of thechallenges and opportunities of these alternative HER-coupled photooxidationreactions for solar energy production and environmental treatment.