Efficient photoelectrochemical conversion of CO2 to syngas by photocathode engineering

Abstract

The synthesis of renewable chemical fuels from CO2 and H2O via photoelectrochemical (PEC) route reprensents a promising room-temperature approach for transforming greenhouse gas into value-added chemicals (e.g., syngas), but to date it has been hampered by the lack of efficient photocathode for CO2 reduction. Herein, we report efficient PEC CO2 reduction into syngas by photocathode engineering. The photocathode is consisting of a planar p-n Si junction for strong light harvesting, GaN nanowires for efficient electron extraction and transfer, and Au/TiO2 for rapid electrocatalytic syngas production. The photocathode yields a record-high solar energy conversion efficiency of 2.3%. Furthermore, desirable syngas compositions with CO/H2 ratios such as 1:2 and 1:1 can be produced by simply varying the size of Au nanoparticle. Theoretical calculations reveal that the active sites for CO and H2 generation are the facet and undercoordinated sites of Au particles, respectively.

Keywords

• Photoelectrocatalysis
• CO2 reduction
• Syngas
• Size effect
• GaN nanowires