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

Improvement of solar-to-chemical energy conversion in photocatalytic CO2 reduction remains fundamentally constrained by insufficient utilization of solar energy, particularly low-energy photons. Here we report a nanoscale greenhouse structure (Bi@Fe2O3) 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 Fe2O3 shell absorbs high-energy photons and serves as the catalytic bed, where injected hot electrons and confined heat synergistically promote CO2 activation and deep hydrogenation. Benefiting from the interplay between photochemical and photothermal effects, the system achieves a CH4 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.