Soft selective light absorber for efficient photothermal chemical processes in complex reactor geometries

Abstract

Photothermal chemical processes are expected to solve the dilemma of fossil energy consumption, but the sunlight-irradiated temperatures of reactors are ∼200 °C, which is insufficient to drive chemical processes. Herein, we have designed a large-scale soft, selective light absorber by spray-coating a two-dimensional MXene layer on Al foil. By optimising the MXene layer thickness, the material achieves 88% solar absorption while limiting infrared radiation to one-fifth. Meanwhile, the excellent flexibility enables the soft, selective light absorber to encapsulate various chemical process reactors (disc, conical, spiral tube), allowing them to reach sunlight-irradiated temperatures of ∼400 °C, more than double those of reactors coated with carbon black powder. Consequently, the three reactors are applied for photothermal gas-state reverse water-gas shift reaction, solid-state CO₂ desorption, and liquid-state methanol reforming reactions, which showed a CO generation rate of >1200 mol g⁻¹ h⁻¹, a CO₂ desorption rate of >3 mL min⁻¹, and a H₂ generation rate of >300 mmol g⁻¹ h⁻¹, respectively, at least 10 times higher than for the reactors coated with carbon black. This work reports retrofitting soft, selective light absorbers to chemical process reactors for the first time, producing efficient photothermal reactors and providing a solid foundation for the future development of the sunlight-driven chemical industry.