Photo-induced CO₂ Reduction with GaN Electrode in Aqueous System

CO 2 reduction with water and light illumination is realized using a gallium nitride (GaN) photoelectrode in which excited electrons induce CO 2 conversion at the counter electrode. For the counter electrode, a copper (Cu) plate was chosen. The low affinity and wide gap of the nitride semiconductor enable us to create an electron–hole pair which has a sufficient energy for both CO 2 reduction and water oxidation, in spite of the fact that a high energy for CO 2 reduction is required. Within this system, the generation of formic acid (HCOOH) with 3% Faradic efficiency was confirmed by light illumination alone.