Enhanced solar-driven hydrogen evolution over ultrathin g-C3N4/ReSe2 heterojunction-like nanosheets with surface selenium vacancies

The design of composite photocatalytic materials is essential for efficient photocatalytic hydrogen production. In the present work, we have successfully designed a simple synthetic process to ultrathin ReSe ₂ nanosheets using an ultrasound-assisted liquid-phase synthetic route through self-assembling ReSe ₂ onto g-C ₃N ₄ (shortened as g-C ₃N ₄/ReSe ₂ nanosheets) to improve photocatalytic performance. Based on density functional theory (DFT) estimation along with experimental characterization, it is found that the integrated heterojunction-like ultrathin g-C ₃N ₄/ReSe ₂ nanosheets possess more edge active sites, enhanced electron transfer efficiency and conductivities, which significantly accelerates the dissociation and migration of photogenerated electron-hole pairs. Meanwhile, selenium vacancies could be introduced into nanosheets via controlling the synthetic procedure with a reduced Se source that will favor to enhance the photocatalytic efficiency. The ultrathin g-C ₃N ₄/ReSe ₂ heterojunction with Se vacancies performed highly improved photocatalytic hydrogen production. In typical, the H ₂ production of the g-C ₃N ₄/ReSe ₂ nanosheets under visible light is 1055.50 μmol g ⁻¹ h ⁻¹, which is 21 times higher than that of bare g-C ₃N ₄, indicating that it overcomes the high charge complexation rate of g-C ₃N ₄. These results do not only provide insight into the application of two-dimensional ReSe ₂ nanosheets in photocatalysis, but also open up new avenues for the rational design of two-dimensional hybrid materials in solar energy conversion.