Solar remediation of wastewater and saline water with concurrent production of value-added chemicals

Significant efforts have been undertaken to develop high-efficiency photoconversion materials and devices for the decentralized in situ production of carbon-neutral chemicals. Notably, photoconversion efficiency is a top priority assuming a ceaseless supply of artificially well-defined water. However, the production of treated water using existing processes is energy-intensive and generates a high carbon footprint. For the practical application of photoconversion systems, the use of untreated water is inevitable. Many organic and inorganic substrates present in untreated water actively participate in the production process of value-added chemicals and interfere with proton–electron transfer kinetics and mechanisms. From this perspective, solar splitting systems with contaminated water and saline water are introduced and the photoconversion systems are classified into photocatalysis, photoelectrocatalysis, and photovoltaic-assisted electrocatalysis. The oxidation and reduction reactions are separately discussed for each system, and hybrid devices developed for treating wastewater and saline water are examined in terms of their mechanism and efficiency.