Turning solar energy into Hydrogen with cuprous oxide

Solar water splitting could convert intermittent solar energy into clean hydrogen. This process requires efficient and cheap photoelectrodes like cuprous oxide with a large photovoltage. Theoretically, cuprous oxide photoelectrodes can reach targets of 14.7 milliamperes per square centimeter and 1.6 Volts — still a significant distance away from the current electrodes, which have reached 10 milliamperes per square centimeter and 1 volt.

Cheng et al. reviewed the current research progress of cost-effective cuprous oxide photoelectrodes applied to solar water splitting, describing factors that limit the improvement of photocurrent density, photovoltage and stability, and the current strategies for overcoming these challenges. The authors also summarize the application of cuprous oxide as top and rear photoelectrodes in unassisted water splitting devices, which do not require external bias to split water and so are more conducive to realizing carbon neutrality.

“For the unbiased tandem device, the advantages and challenges using cuprous oxide as the top electrode and rear electrode need to be clarified, and the development of corresponding strategies is crucial to fully benefit the solar-fuel conversion,” author Jingshan Luo said.

“Our review not only helps the reader quickly understand the research status of cuprous oxide photoelectrodes, but also serves as a valuable reference for modifying other photoelectrode or photovoltaic materials,” author Jinshui Cheng added.

The authors hope to highlight several directions in cuprous-oxide materials for readers, such as the effects of defects on properties such as photocurrent density and photovoltage, optimization of unbiased tandem device structures, and the replacement of oxygen production with higher value-added reactions such as biomass oxidation.

Source: “Cuprous oxide photocathodes for solar water splitting,” by Jinshui Cheng, Linxiao Wu, and Jingshan Luo, Chemical Physics Reviews (2022). The article can be accessed at https://doi.org/10.1063/5.0095088 .