Photoelectrochemical CO₂ Reduction into Syngas with the Metal/Oxide Interface

Photoelectrochemical (PEC) reduction of CO₂ with H₂O not only provides an opportunity for reducing net CO₂ emissions but also produces value-added chemical feedstocks and fuels. Syngas, a mixture of CO and H₂, is a key feedstock for the production of methanol and other commodity hydrocarbons in industry. However, it is challenging to achieve efficient and stable PEC CO₂ reduction into syngas with controlled composition owing to the difficulties associated with the chemical inertness of CO₂ and complex reaction network of CO₂ conversion. Herein, by employing a metal/oxide interface to spontaneously activate CO₂ molecule and stabilize the key reaction intermediates, we report a benchmarking solar-to-syngas efficiency of 0.87% and a high turnover number of 24 800, as well as a desirable high stability of 10 h. Moreover, the CO/H₂ ratios in the composition can be tuned in a wide range between 4:1 and 1:6 with a total unity Faradaic efficiency. On the basis of experimental measurements and theoretical calculations, we present that the metal/oxide interface provides multifunctional catalytic sites with complementary chemical properties for CO₂ activation and conversion, leading to a unique pathway that is inaccessible with the individual components. The present approach opens new opportunities to rationally develop high-performance PEC systems for selective CO₂ reduction into valuable carbon-based chemicals and fuels.