Photoelectrochemical CO2 electrolyzers: From photoelectrode fabrication to reactor configuration

The photoelectrochemical conversion of CO2 into value-added products emerges as an attractive approach to alleviate climate change. One of the main challenges in deploying this technology is, however, the development and optimization of (photo)electrodes and photoelectrolyzers. This review focuses on the fabrication processes, structure, and characterization of (photo)electrodes, covering a wide range of fabrication techniques, from rudimentary to automated fabrication processes. The work also highlights the most relevant features of (photo)electrodes, with special emphasis on how to measure and optimize them. Finally, the review analyses the integration of (photo)electrodes in different photoelectrolyzer architectures, analyzing the most recent research work that comprises photocathode, photoanode, photocathode-photoanode, and tandem photoelectrolyzer configurations to ideally achieve self-sustained CO2 conversion systems. Overall, comprehensive guidelines are provided for future advancements in developing effective devices for CO2 conversion, bridging the gap towards the use of sunlight as the unique energy input and practical applications.