Selective CO2 photoreduction to acetate enabled by charge-enriched interface sites confined in metal nanoclusters.

Supported metal nanoclusters, recognized for their distinct electronic properties and high density of exposed active sites, present promising prospects for CO2 photoconversion. Nevertheless, achieving efficient C-C coupling toward C2 products remains a considerable challenge due to the inherently high energy barrier involved. The rational design of such catalysts is further hindered by the absence of effective descriptors. In this work, we establish for the first time that the work function can serve as a key descriptor to predict the C-C coupling barrier. It is revealed that supported metal nanoclusters with moderate work functions facilitate the formation of electron-enriched interface sites, which substantially lower the C-C coupling barrier and steer the reaction pathway away from CO* desorption or over-hydrogenation toward selective C2 generation. Guided by this principle, Pt clusters supported on reduced graphene oxide (Pt-rGO) were designed, featuring an optimal work function of 4.546 eV, and were successfully synthesized via a controlled photodeposition method. The resulting Pt-rGO catalyst achieves an exceptional acetate production rate of 29.63 μmol g-1 h-1 with 91.8% selectivity. Mechanistic studies including quasi in-situ synchrotron-radiation X-ray photoelectron spectra, charge density analysis, and crystal orbital overlap population calculations confirm that the electron-rich Pt sites at the interface promote CO2 activation and stabilize key C2 intermediates through enhanced electron donation. This work underscores the critical role of electron-rich metal-support interfaces in directing CO2 photoreduction toward multi-carbon products, paving the way for descriptor-driven catalyst design.