Excitonic quantum superlattices for efficient photocatalytic water splitting

Producing clean hydrogen directly from sunlight and water has emerged as a promising path for achieving carbon neutrality and environmental sustainability. However, the inefficient utilization of photogenerated charge carriers in photocatalysts hinders the solar-to-hydrogen efficiency. Here we show the use of excitonic quantum superlattice structures, consisting of nanometer-scale gallium nitride (GaN) and indium gallium nitride (InGaN), to achieve ideal charge steering for photocatalytic overall water splitting (OWS). With this structure, the lifetime of photogenerated indirect excitons, composed of electrons and holes via Coulomb interaction, can be significantly prolonged by exploiting the prominent quantum-confined Stark effect (QCSE) As a result, carriers excited can be near-perfectly utilized for surface reactions, achieving high external quantum efficiency (EQE) extended to visible light and a high STH efficiency of 3.16% under room temperature and ambient pressure. Furthermore, outdoor scale-up demonstration achieved an average STH efficiency of 1.64% under 204-fold sunlight intensity.