A photothermal catalysis flow cell represents a sophisticated fusion of solar-thermal energy and chemical engineering. While standard photoelectrochemical (PEC) cells use sunlight to move electrons, photothermal systems use the entire solar spectrum (UV, visible, and Infrared) to generate intense localized heat on a catalyst surface. This heat lowers the activation energy of chemical reactions, allowing for "thermal" catalysis—like the Sabatier reaction or CO₂ hydrogenation—to occur using only concentrated sunlight, without the need for external furnaces or high-pressure steam. 

In a continuous flow cell for photothermal generation, the stack is designed to trap heat while moving gases or liquids. (1) Optical Window: A double-pane quartz or high-borosilicate window is used. The gap between panes is often vacuum-sealed to provide thermal insulation, preventing the "greenhouse" heat from escaping the reactor. (2) Photothermal Absorber/Catalyst: This is the heart of the cell. It is typically a flow-through porous matrix (like a ceramic foam, metallic sponge, or carbon felt) coated with "black" plasmonic nanoparticles (e.g., Ru, Ni, or Au) or semiconductors like black TiO₂. These materials are engineered to have near-perfect solar absorbance (low reflectance). (3) Heat Localization: Unlike a standard oven that heats the whole room, these cells use nanoscale heating. The photons strike the nanoparticles, causing "localized surface plasmon resonance" (LSPR) or vibrational excitation, heating the catalyst surface to hundreds of degrees Celsius while the surrounding reactor body stays relatively cool.

References:

1. X. Wang, et al., A nonmetallic plasmonic catalyst for photothermal CO2 flow conversion with high activity, selectivity and durability, Nature Communications, 2024, 15, 1273. 

2. H. He, et al. Continuous Flow Photothermal Catalytic CO2 Reduction: Materials, Mechanisms, and System Design, ACS Catal. 2025, 15, 12, 10480–10520.