Band Engineering Induced by Sulphur Vacancies in MoS/g-CN or Selective CO Photoreduction to CHOH.

Developing photocatalysts with both high efficiency and reaction pathway selectivity is essential for achieving efficient and sustainable CO conversion. By incorporating sulphur vacancies into MoS, an S-scheme heterojunction photocatalyst (MoS-SVs/g-CN) was developed, achieving efficient and selective CO photoreduction to CHOH. The structural and photoelectronic characterisation of the system shows that the heterogeneous interface between MoS and g-CN is in close contact. The introduction of SVs effectively modulates the electronic structure and surface activity of MoS, which in turn enhances the CO reduction performance. Optical and electronic structure analyses reveal that the heterojunction promotes favourable band alignment and interfacial electric potential gradients, which together suppress charge recombination and enhance directional carrier separation. Under irradiation, the MoS-SVs/g-CN photocatalyst exhibited outstanding photocatalytic CHOH production with a yield of 10.06 μmol·h·g, significantly surpassing the performance of control samples while demonstrating excellent product selectivity and remarkable stability. Mechanistic studies further verify that vacancy-induced energy band modulation with Fermi energy level enhancement significantly reduces the multi-electron transfer barrier, thus preferentially driving the CHOH generation pathway. This work proposes a universal structural design strategy that synergistically coordinates vacancy engineering with band structure modulation, establishing both theoretical principles and practical methodologies for developing selective multi-electron CO reduction systems.