Identifying Reactive Sites and Surface Traps in Chalcopyrite Photocathodes

Gathering information on the atomic nature of reactive sites and trap states is key to fine tuning catalysis and suppressing deleterious surface voltage losses in photoelectrochemical technologies. Here, spectroelectrochemical and computational methods were combined to investigate a model photocathode from the promising chalcopyrite family: CuIn0.3Ga0.7S2. We found that voltage losses are linked to traps induced by surface Ga and In vacancies, whereas operando Raman spectroscopy revealed that catalysis occurred at Ga, In, and S sites. This study allows establishing a bridge between the chalcopyrite's performance and its surface's chemistry, where avoiding formation of Ga and In vacancies is crucial for achieving high activity.
Spectroelectrochemical and computational methods are combined to shed light on the promising reactivity of semiconductor chalcopyrites towards hydrogen production via photoelectrochemical (PEC) water splitting. A direct correlation between the PEC response and the chemical nature of the catalytic interface is presented, providing guidelines for engineering the performance of chalcopyrites.