Stand‐Alone Photoelectrochemical Energy Conversions

The photoelectrochemical (PEC) conversions of water and atmospheric CO 2 to value‐added fuels, such as H 2 , CH 4 , and CH 3 OH, can provide potential alternative sources for clean and environment‐friendly solar fuels. Several efforts are reported on the designing and developing stand‐alone PEC cells that efficiently produce H 2 and O 2 from water and minimize atmospheric CO 2 via conversion to fuels under only sunlight. However, in reality, high overpotential, poor product‐selectivity, competitive side‐reactions, and self‐reduction of a catalyst limit the performance of the PEC cells, thereby requiring high power inputs. The choice of electrode materials and architectures of PEC cells are very important for designing stand‐alone and durable PEC cells with high solar‐to‐fuels conversion efficiency ( Eff STF ) and high selectivity. The present review provides a complete account of recent published works on stand‐alone PEC systems with different architectures; development of electrode materials for high Eff STF , selectivity, and stability; and the current challenges. Furthermore, this review describes the future outlook on stand‐alone PEC systems for future production of clean solar fuels and mitigation of atmospheric CO 2 levels by utilizing only solar energy.