Hybrid Mie Resonator Photocatalysts as a Platform for Solar Chemicals: Quantification of Light-Induced Electronic Effect versus Heating Effect

Solar-to-chemical energy conversion via carbon-carbon (C-C) coupling provides a promising route for producing energy-dense molecules under sustainable conditions. Here, we report the design and implementation of hybrid CuO-Pd Mie resonator photocatalysts for the oxidative homocoupling of phenylacetylene to 1,4-diphenylbutadiyne. The integration of Pd nanoclusters with dielectric CuO nanostructures enables efficient light absorption and interfacial charge separation across a Schottky junction, collectively driving enhanced photocatalytic activity. The hybrid nanocatalyst exhibits complete conversion with excellent selectivity under visible-light irradiation, while base-free conditions further highlight its environmental compatibility. We quantified and differentiated light-induced electronic effects from light-induced heating effects. At ambient temperature (∼28 °C), irradiation at 0.3 sun produced a 3.3-fold enhancement in the reaction rate (i.e., 230% increase) relative to dark conditions (∼26 °C), indicating a significant contribution from light-induced electronic effects. Increasing the illumination intensity to 1 sun raises the reaction temperature to ∼115 °C without external heating. Further, it enhances the reaction rate by 4.8-fold (i.e., 380% increase) compared to dark-heating conditions, demonstrating a strong dependence of catalytic activity on photon flux. Control experiments reveal negligible activity for pristine CuO, confirming the essential role of Pd in facilitating bond formation. Transient reflection measurements confirm that interfacial electron transfer from CuO to Pd governs enhanced reactivity. Overall, this work establishes CuO-Pd Mie resonators as an earth-abundant platform for solar light-driven C-C coupling, offering an example pathway to decarbonize chemical synthesis while advancing solar-to-chemical energy conversion technologies.