Visible-Light-Driven Photocatalytic Water Splitting: Recent Progress and Challenges

Water splitting with sunlight and photocatalysts is a promising means of producing hydrogen as a sustainable future energy supply. New visible-light-responsive photocatalytic materials, such as (oxy)nitrides, (oxy)chalcogenides, oxychlorides, conjugated polymers, and doped or dye-sensitized oxides, have been utilized in one- and two-step-excitation visible-light-driven overall water-splitting systems. The efficiency of the photocatalytic overall water-splitting reaction has been significantly improved but further increases are still needed for practical large-scale applications. Various strategies have been proposed to develop photocatalytic water-splitting systems to allow for practical applications. Sunlight-driven photocatalytic water splitting is one of the most promising approaches to generating renewable hydrogen as an energy source. In recent years, significant progress has been made in the development of photocatalytic water-splitting systems. Among these, the one- and two-step-excitation overall water-splitting processes are most widely investigated. Realization of visible-light-driven overall water splitting is one of the most important goals at present because of the need to obtain systems exhibiting high solar-to-hydrogen energy conversion efficiency for practical applications. The present review focuses on recent progress in the field of photocatalytic water splitting, especially in the research and design of visible-light-driven overall water-splitting systems, and outlines potential strategies to overcome the difficulties related to practical applications. Sunlight-driven photocatalytic water splitting is one of the most promising approaches to generating renewable hydrogen as an energy source. In recent years, significant progress has been made in the development of photocatalytic water-splitting systems. Among these, the one- and two-step-excitation overall water-splitting processes are most widely investigated. Realization of visible-light-driven overall water splitting is one of the most important goals at present because of the need to obtain systems exhibiting high solar-to-hydrogen energy conversion efficiency for practical applications. The present review focuses on recent progress in the field of photocatalytic water splitting, especially in the research and design of visible-light-driven overall water-splitting systems, and outlines potential strategies to overcome the difficulties related to practical applications. the ratio of photons contributing to an intended reaction to the photons irradiated to the photocatalyst. It reflects how efficiently incident photons are utilized in the intended photocatalytic reaction. redox mediators and conducting materials that can transfer electrons between the hydrogen evolution photocatalyst and the oxygen evolution photocatalyst. a process in which only one photocatalyst is excited to produce reactive electrons and holes during photocatalysis. a reversible donor/acceptor ionic couple that can be oxidized by a hydrogen evolution photocatalyst or reduced by an oxygen evolution photocatalyst, respectively. It is often used in the two-step-excitation water-splitting system. the ratio of solar energy stored as hydrogen to the incident solar energy. It reflects how much incident solar energy is harvested via the water-splitting reaction by a photocatalyst. an electron donor or acceptor that is efficiently and irreversibly oxidized or reduced by a photocatalyst. They consume photogenerated holes or electrons, respectively, and can promote the photocatalytic hydrogen or oxygen evolution half-reaction.