Highly Aqueous Stability of Metal Oxides Encapsulated CsPbBr₃ Nanocrystals via A Generalized Core-Shell Engineering

Metal halide perovskite nanocrystals (NCs) are promising luminescent materials for optoelectronic applications. However, the highly sensitive nature of the perovskite lattice to water significantly limits the perovskite NCs for photocatalysis in aqueous phase. Here, we present a core-shell engineering strategy based on an epoxide-mediated sol-gel process to grow metal oxides on the surfaces of perovskite NCs. Benefit from the versatile inorganic metal salts, different metal oxides (such as SnO₂, Al₂O_3, and Eu₂O₃) are deposited onto the perovskite core under ambient conditions. Owing to the protection of dense metal oxide shell, the exemplified SnO₂@CsPbBr₃ NCs display intense emission after annealing and slightly photoluminescence (PL) quenching in water over 30 days. Interestingly, they additionally behave outstanding dispersibility in water (with a zeta potential of ∼42 mV). These features, combined with the type II band alignment of SnO₂@CsPbBr₃ NCs facilitating the photo-generated charge separation, result in a NH₄ ⁺ production rate of 47 µmol g^-1·h^-1 without any sacrificial agents. This work explores a generalized approach to produce core-shell structured perovskite NCs to enhance their aqueous stability. Besides, it also expands the aqueous applications of perovskite communities and gives a guideline for designing novel nitrogen fixation photocatalysts.