K+-Intercalated carbon nitride with electron storage property for high-efficiency visible light driven nitrogen fixation

Photocatalytic nitrogen fixation is one of the most promising sustainable energy conversion technologies and might serve as a cheaper and more energy-efficient alternative to the capital- and energy-intensive Haber-Bosch process. However, the solution to solve the nitrogen fixation kinetic problem induced by high reduction potential of intermediates remains a grand challenge. In this work, the kinetic problem of nitrogen fixation is addressed under ambient conditions using K+-intercalated crystalline carbon nitride (KCCN) with an electron storage property. Combined with vigorous N2 chemisorption and activation properties of nitrogen vacancies (NVs), a photocatalytic nitrogen fixation system is constructed, where the NVs on KCCN chemisorb and activate N2 molecule, and subsequently reduce it to NH3 by multielectron reactions facilitated by the stored electrons of KCCN. The unique structure of KCCN-NVs demonstrates a high NH3 production rate of 3.51 mmol h−1 g−1 under visible light irradiation and an apparent quantum yield of 2.05% at λ = 430 nm. This work offers an intriguing solution toward the development of nitrogen-fixing photocatalysts.