Nanoscale greenhouse effect for promoting solar-driven CO2 reduction with water to CH4

Improvement of solar-to-chemical energy conversion in photocatalytic CO 2 reduction remains fundamentally constrained by insufficient utilization of solar energy, particularly low-energy photons. Here we report a nanoscale greenhouse structure (Bi@Fe 2 O 3 ) that enables cascaded utilization of full solar spectrum. The Bi nanocore primarily absorbs low-energy photons, generating localized nanoheating via non-radiative heating through localized surface plasmon resonance effects and energetic hot electrons. Meanwhile, the oxygen-vacancy-rich loose Fe 2 O 3 shell absorbs high-energy photons and serves as the catalytic bed, where injected hot electrons and confined heat synergistically promote CO 2 activation and deep hydrogenation. Benefiting from the interplay between photochemical and photothermal effects, the system achieves a CH 4 production rate of 273.81 μmol g –1 h –1 with 98.60% selectivity and an apparent quantum efficiency of 0.64% at 850 nm illumination without any external heating or sacrificial agents. This work paves a way for the efficient utilization of the entire solar spectrum.