Photocatalytic back-conversion of CO2 into oxygenate fuels using an efficient ZnO/CuO/carbon nanotube solar-energy-material: Artificial photosynthesis

•A solar-based atomistic-hydrogenation strategy for CO2 conversion to oxygenate fuels.•In the presence of CNT, artificial photosynthesis could be appreciably enhanced.•Eco-friendly low-price solar-energy-materials for CO2 photoconversion using water H source.•A facile hydrothermal route for the synthesis of efficient nanocomposite photocatalysts.

Fuel shortage, energy crisis and boundless dumping of greenhouse gases into the atmosphere, are some challenging issues of human societies. To overcome these energy-related/environmental problems, solar conversion of CO2 to carbon-based fuels is a promising route, which is achievable through the atomistic hydrogenation of CO2 molecules inside semiconductor-assisted water-photosplitting reactors. In this paper, using a facile hydrothermal method, an eco-friendly, low-price, nanocomposite solar-energy-material was synthesized in the absence and presence of carbon nanotube (CNT), and applied in aqueous media for the photochemical synthesis of ethanol, oxalic acid and formaldehyde. The enhancing power of CNT on the photocatalyst performance was explained in detail in terms of its ability to harvest more incident photons, temporarily store H atoms, increase the surface area and improve the charge separation phenomenon. Based on atomistic hydrogenation hypothesis, a reaction scheme was finally proposed for each photochemically synthesized product.