Photo‐ and Electrocatalytic CO2 Reduction Based on Stable Lead‐Free Perovskite Cs2PdBr6

All‐inorganic lead‐free palladium (Pd) halogen perovskites with prominent optoelectronic properties provide admirable potential for selective photo‐ and electroreduction of CO2. But it remains unachieved for effectively converting the CO2 to CO with high selectivity on Pd‐based perovskites driven by solar light or electricity. Herein, high‐quality Cs2PdBr6 microcrystals and nanocrystals were synthesized through a facile antisolvent method. Among all the reported pure‐phase perovskites, the Cs2PdBr6 nanocrystals synthesized at 50 °C performed the highest effectiveness on CO2 to CO conversion generating 73.8 μmol g−1 of CO yield with 100% selectivity under visible light illumination (λ > 420 nm) for 3 h. Meanwhile, for the first time, we report a new application of lead‐free perovskites, in which they are applied to electrocatalysis of CO2 reduction reaction. Noticeably, they showed significant electrocatalytic activity (Faradaic yield: 78% for CO) and operation stability (10 h). And the surface reaction intermediates were dynamically monitored and precisely unraveled according to the in situ diffuse reflectance infrared Fourier transform spectra investigation. In combination with the density functional theory calculation, the reaction mechanism and pathways were revealed. This work not only provides significant strategies to enhance the photocatalytic performance of perovskites, but also shows excellent potential for their application in electrocatalysis.