Fabricating 2D/2D/2D heterojunction of graphene oxide mediated g-C3N4 and ZnV2O6 composite with kinetic modelling for photocatalytic CO2 reduction to fuels under UV and visible light

Abstract

Two dimensional (2D) reduced-graphene-oxide/g-C3N4 modified 2D ZnV2O6 heterojunction for enhanced photocatalytic CO2 reduction has been investigated. The catalysts were fabricated using one-pot solvothermal method and were tested in a fixed-bed reactor under visible and UV-light. The ZnV2O6/RGO/g-C3N4 composite catalyst demonstrated excellent photoactivity for CO2 reduction to CO and hydrocarbons under visible light. The maximum CO yield rate of 2802.9 µmol g-1 h-1 was obtained over the composite, which is 7.4 and 1.7 times higher than using g-C3N4 and ZnV2O6, respectively. The improved activity attributing to synergistic effect of 2D layer heterojunction with enhanced charges separation by RGO mediator under visible light. Comparatively, 2 times lower productivity was obtained under UV-light than visible-light due to higher visible-light absorption. The time-dependent kinetic-model was further developed to understand the influence of photocatalytic oxidation and reduction processes on the reaction chemistry. The model is based on Langmuir–Hinshelwood (L–H) mechanism to understand the formation rates of products during photocatalytic CO2 conversion with water vapours. Kinetic reveals surface reaction is a rate limiting step, which depends on the generation of charge carrier with higher light absorption. The findings from the experimental and kinetic-model would be useful to understand photo-catalytic reaction engineering in solar energy applications. Graphical abstract: [Figure not available: see fulltext.]