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

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 CO₂ conversion remains a critical challenge. Herein, the fabrication of a sandwich-like organic–inorganic hybrid perovskite-based photocathode with carbon encapsulation for PEC CO₂ 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 CO₂-saturated 0.5 m KHCO₃ 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 CO₂ 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%.