Steering Heat and Molecules: Directional Freeze-Cast Aerogel Shells Boost Photothermal CO2 Methanation

Abstract

Developing integrated systems that merge efficient CO2 capture with rapid photothermal catalysis (PTC) remains a formidable challenge in sustainable catalysis. Herein, the developed 3D-microporous chitosan aerogel (CA) encapsulated Ni/ZrO2 catalyst (Ni/ZrO2@CA) not only maximizes photothermal harvesting through multiple light-scattering effects but also provides abundant, atom-dispersed −NH2 sites that function as Lewis basic centers for CO2 capture and activation, forming carbamate intermediates. Under simulated solar irradiation (2400 mW·cm–2), Ni/ZrO2@CA achieved CH4 production rates up to 297.0 mmol·gcat–1·h–1 with 99.8% selectivity, representing up to a 10–16-fold enhancement over pristine Ni/ZrO2. In situ DRIFTS detected carbamate species under reaction conditions, and DFT calculations suggest an NH2-mediated capture–hydrogenation–displacement pathway that may circumvent high-energy barriers associated with direct CO2 activation. This work establishes a new design paradigm in which the organic overlayer acts as a molecular cocatalyst, transforming integrated CO2 capture and utilization into a single photothermal microreactor platform.