Recent Improvements in the Production of Solar Fuels: From CO2 Reduction to Water Splitting and Artificial Photosynthesis

This account deals with recent trends and challenges regarding photo(electro)chemical solar fuels produced by CO2 reduction and water splitting. The CO2 reduction process is limited by product selectivity, catalyst stability, and its complex reaction mechanism. A variety of catalysts-including thermocatalysts, photocatalysts, electrocatalysts, and combinations of photo-and electrocatalysts-have been employed to facilitate selective and durable CO2 reduction. In addition, the roles of the supporting electrolyte, pH, reaction temperature, chemical environment, and catalyst surface chemistry in efficient CO2 reduction have been thoroughly studied in recent years. Effective use of solar light is a significant part of realizing efficient solar-to-hydrogen conversion during the water splitting process, and so the response of photo(electro) systems to visible light is key. To this end, several strategies have been studied in detail, including band engineering of photocatalysts, photocatalytic systems that mimic natural photosynthesis, and the development of photoanodes and their combination with photovoltaic systems. Here, we summarize recent developments surrounding the CO2-reduction and water-splitting reactions and progress towards achieving artificial photosynthesis.