A Strategy for Synergistic Photothermal-Photocatalytic: Contactless Photocatalytic Reactor for CO 2 Reduction with Seawater or Wastewater into HCOOH

<title>Abstract</title> <p>Herein, a synergistic photothermal-photocatalytic strategy is developed by designing a contactless photocatalytic reactor that concurrently synchronizes and enhances mass transfer while expanding the scope of usable water sources. Specifically, heat radiation-induced evaporation is exploited to accelerate the transport of both reactants and products, thereby relaxing the purity requirements for the water feedstock and sustaining efficient CO₂ reduction rates even with seawater and wastewater. Importantly, the diffusion rates of vaporized H₂O and CO₂ reach the same order of magnitude, effectively eliminating the mass-transfer mismatch. Under full-spectrum irradiation in a reactor with a 1 cm² irradiation area, the CO₂-to-formic acid production rates using pure water, simulated seawater, and simulated wastewater reach 680.7, 645.3, and 663.0 µmol g⁻¹ h⁻¹, respectively. This work not only demonstrates the valorization of wastewater resources but also opens a new avenue for integrated photocatalysis and photothermal conversion.</p>