Carbon Encapsulation of Organic–Inorganic Hybrid Perovskite toward Efficient and Stable Photo‐Electrochemical Carbon Dioxide Reduction

Abstract Photo‐electrochemical (PEC) carbon dioxide reduction to chemicals or fuels has been regarded as an attractive strategy that can close the anthropogenic carbon cycle. However, identifying a PEC system capable of driving efficient and durable CO 2 conversion remains a critical challenge. Herein, the fabrication of a sandwich‐like organic–inorganic hybrid perovskite‐based photocathode with carbon encapsulation for PEC CO 2 reduction is reported. The carbon encapsulation not only affords protection to the perovskite, but also allows for efficient conductance of photogenerated electrons. When decorated with a cobalt phthalocyanine molecular catalyst, the photocathode shows an onset potential at 0.58 V versus reversible hydrogen electrode (RHE) and a high photocurrent density of −15.5 mA cm −2 at −0.11 V versus RHE in CO 2 ‐saturated 0.5 m KHCO 3 under AM 1.5G illumination (100 mW cm −2 ), which represents state‐of‐the‐art performance in this field. Moreover, the photocathode remains stable during a continuous reaction that lasted for 25 h. Unbiased PEC CO 2 reduction is further realized by integrating the photocathode with an amorphous Si photoanode in tandem, delivering a solar‐to‐CO energy conversion efficiency of 3.34% and a total solar‐to‐fuel energy conversion efficiency of 3.85%.