LAUSR

Sunlight-powered reduction of CO2 to fuels and chemicals is a promising strategy to close the carbon loop and facilitate the energy transition. In this research, we demonstrate that Au nanoparticles supported on TiO2 are an efficient plasmonic catalyst for the sunlight-powered reverse water-gas shift (rWGS) reaction. A maximum CO production rate of 429 mmol ·gAu 1 ·h 1 with a selectivity of 98% and an apparent quantum efficiency of 4.7% were achieved using mildly concentrated sunlight (1.44 W·cm 2 equals 14.4 sun). The CO production rate showed an exponential increase with increasing light intensity, suggesting that the process is mainly promoted by a photothermal effect. Thermal reference experiments with the same catalysts promoted CH4 formation, dropping the CO selectivity to 70%. Thus, mildly concentrated sunlight can efficiently and selectively enhance the promotion of the rWGS reaction without using external heating. Reduction of CO2 to fuels and chemicals is an important technology that will contribute to achieving a carbon neutral society. CO2 can be considered as a non-toxic, cheap and abundant feedstock to make synthetic fuels and chemicals. However, its activation requires high amounts of energy. Several technologies to convert CO2 into fuels and chemicals have emerged in the last decades, such as biochemical, electrochemical, thermochemical, plasma chemical and photochemical. Photocatalysis aims to directly harvest (sun) light and transfer its energy to convert CO2 into fuels and chemicals. Different products can be targeted through (sun) light-powered CO2 hydrogenation, with methane (CH4) and carbon monoxide (CO) as the main target products. Recently, plasmonic hydrogenation of CO2 to CH4 [Sabatier reaction, Eq. (1)] has been reported with high production rates using Ru and Ni based catalysts at low catalyst bed temperatures. CO is an interesting product to target due to the great potential it offers as a building block to synthesize long chain hydrocarbons through the well-established FischerTropsch synthesis (FTS). CO2 is hydrogenated to CO via the reverse water-gas shift (rWGS) reaction [Eq. (2)]. The combination of the rWGS reaction and the FTS constitutes a two-step process which has potential to become a green technology for the production of synthetic fuels with large demand using CO2 as a feedstock.