Co‐Catalyst Free Efficient Photocatalytic CO 2 Reduction Using Facet‐Engineered Polyhedral CsPbBr 3 Perovskite Nanocrystals

Abstract In the quest for efficient photocatalysts, cancrystal shape engineering outperform size reduction in enhancing photocatalytic performance? This is investigated using CsPbBr 3 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 2 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 2 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.