Interfacial Photoelectrochemical Catalysis: Solar-Induced Green Synthesis of Organic Molecules

Many oxidation and reduction reactions in conventional organic synthesis rely on harsh conditions, toxic or corrosive substances, and environmentally damaging chemicals. In addition, competing reactions may take place, some of which produce hazardous waste products and, therefore, reaction selectivity suffers. To overcome such synthetic drawbacks, an enormous effort is being devoted to find alternative processes that operate much more efficiently, requiring milder conditions to contribute to a greener economy and provide urgently needed new pathways with enhanced selectivity. Fortunately, there is a strategy that has attracted global interest from multiple disciplines that involves the use of sunlight to perform artificial photosynthesis, in which a photoelectrochemical cell splits water into hydrogen fuel, reduces CO₂ into "solar" fuels, and more recently, convert organic chemicals into higher value products. Recently, photoanode and photocathode materials have emerged as useful tools to perform organic oxidations and reductions for the synthesis of important molecules, other than just hydrogen or oxygen. Whereas many studies have focused on the degradation of unwanted and dangerous chemicals, solar-induced organic transformations have attracted much less attention. This Minireview summarizes some of latest research efforts in using photoelectrochemical cells to facilitate organic oxidation and reduction reactions to avoid valuable substances while avoiding toxic reagents and expensive precious metal catalysts. Future developments that will enable such technologies to broaden their scope are also considered.