Co-Catalyst Free Efficient Photocatalytic CO2 Reduction Using Facet-Engineered Polyhedral CsPbBr3 Perovskite Nanocrystals

In the quest for efficient photocatalysts, cancrystal shape engineering outperform size reduction in enhancing photocatalytic performance? This is investigated using CsPbBr<inf>3</inf> perovskite nanocrystals (PNC) by comparing conventional amine-capped, 6-facet cubic morphology with newly developed 26-facet polyhedral nanocrystals synthesized via an amine-free approach. Surprisingly, the larger polyhedral PNCs are far better at converting CO<inf>2</inf> into CO, despite their lower surface-to-volume ratio than the 6-facet cubic PNCs. They achieve a total CO yield of 394 µmol g⁻¹ with a conversion rate of 35.81 µmol g⁻¹ h⁻¹ without any help from extra co-catalysts. To the best of the author's knowledge, this represents the highest reported CO evolution rate using 3-dimensional PNCs as the sole photocatalyst, with performance comparable to or exceeding systems employing co-catalysts. This enhanced activity arises from longer excited-state lifetimes, improved charge transport, larger electrochemical surface area (ECSA), and a higher density of charge carriers, as confirmed by optical and electrochemical studies. Computational studies show that some specific facets of this polyhedra bind CO<inf>2</inf> molecules more strongly and provide the optimized binding energy to efficiently release the final product(CO). With excellent 12-h stability, these shape-controlled nanocrystals enable a pathway toward sustainable energy technology applications worldwide.