Bifunctional g-GaN/Si9C15 S-scheme heterojunction for efficient photocatalytic hydrogen evolution and photodetector

S-scheme heterojunctions are commonly applied in optoelectronic devices and photocatalytic materials to achieve effective charge separation and enhance photocatalytic activity. In this study, the electronic, optical, and electrical behaviors as well as the photocatalytic water splitting performance of the g-GaN/Si9C15 S-scheme heterojunction have been researched using first-principles. The results suggest that the g-GaN/Si9C15 heterojunction is energetically, thermally, and dynamically stable. The g-GaN/Si9C15 heterojunction belongs to the S-scheme photocatalyst with the g-GaN as the oxidant and the Si9C15 as the reductant, and its band edge positions cross the standard water oxidation and reduction potentials. The g-GaN/Si9C15 heterojunction has a power conversion efficiency of 11.03 % and a large carrier mobility of 20.98 × 103 cm2 V−1 s−1. The small overpotential of 0.076 V is favorable for the occurrence of the hydrogen evolution reaction, and the oxygen evolution reaction of the g-GaN/Si9C15 heterojunction can spontaneously proceed when U = 1.23 V. The g-GaN/Si9C15 heterojunction exhibits a large solar-to-hydrogen efficiency of 25.58 %. Moreover, the g-GaN/Si9C15 heterojunction has a high photocurrent and a large extinction ratio. In conclusion, the g-GaN/Si9C15 heterojunction holds potential applications in photocatalytic water splitting and photodetector.