Facile synthesis of new, highly efficient SnO2/carbon nitride composite photocatalysts for the hydrogen evolution reaction

Abstract

Novel SnO₂/carbon nitride photocatalysts having surface areas up to 220 m² g⁻¹ were prepared for the first time by condensation of dicyandiamide in alkali metal chloride/SnCl₂-containing salt melts at 550 °C, without the use of hard templates. XRD and HR-TEM investigations showed that the obtained materials are composed of 5–10 nm SnO₂ nanoparticles deposited onto nanosheets set up from 1D-melon ribbons. The morphology and crystalline structure of products appear to be greatly dependent on the synthesis temperature. SnO₂/carbon nitride composites are found to be highly efficient in the photocatalytic reactions, as exemplified by Rhodamine B degradation and water reduction using Pt as a co-catalyst. Under the optimized synthesis conditions, these composite photocatalysts achieve hydrogen evolution rates more than 2 times higher than the mesoporous carbon nitride (mp-CN) under visible light irradiation. In principle, this new method based on utilization of MCl/SnCl₂ salt melts as a reaction medium allows carrying out various polymerization reactions in the presence of the mild Lewis acid in the solution phase in the wide temperature range of 180–550 °C. Moreover, SnCl₂ eutectics are even suitable for post-synthesis modification of the bulk carbon nitride to tune its morphology and greatly increase the surface area and photocatalytic activity.