Application of single-atom-based photocatalysts in environmental pollutant removal and renewable energy production

Green and clean photocatalytic technology has been extensively applied to degrade environmental pollutants and produce renewable energy, which is an important mean to solve environmental and energy problems. However, limited to the cost and efficiency of photocatalysts, it is difficult to realize large-scale application. In recent years, the single-atom photocatalysts (SAPCs) have added new vitality into this field. SAPCs have the active homogeneous centers, heterogeneous structures, stability, high catalytic activity and selectivity properties. The related researches on its synthesis, characterization and application have become a hot spot in many fields. In this review, the photocatalytic H2 production, CO2 reduction, nitrogen fixation, NOx removal, volatile organic compounds removal, pollutant degradation, reduction of radionuclides and heavy metal ions using SAPCs are reviewed. The advantages and disadvantages of the six kinds of SAPCs substrates are analyzed, and design strategies are carefully summarized. The mechanisms of photocatalysis, isolated-site reactions, photogenerated e--h(+) transfer and the construction of efficient photoactivation cycles are discussed. Finally, the future development trend of SAPCs is prospected. This review will provide a reference for the design of high efficiency SAPCs.HIGHLIGHTSThe structures, characteristics and synthesis of SAPCs with different substrates are reviewed.The applications of SAPCs and their photocatalytic removal for different pollutants are introduced.The photocatalytic reaction processes and mechanisms for different pollutants are discussed.The development direction and challenges of SAPCs in the field of environmental energy are prospected.