Engineering high-coordinated cerium single-atom sites on carbon nitride nanosheets for efficient photocatalytic amine oxidation and water splitting into hydrogen

Developing highly-active rare-earth single atom photocatalysts have attracted extensive attention due to their excellent catalytic properties. Herein, we prepared a single-atom Ce-SA-C 3 N 4 catalyst composed of atomically dispersed rare-earth cerium (Ce) on C 3 N 4 nanosheets by the pyrolysis of cerium-incorporated layered precursor. The atomic distribution and high-coordinated environment of Ce sites were disclosed by aberration-corrected scanning transmission electron microscopy, electron energy-loss spectra, X-ray absorption spectroscopy, and theoretical calculations. In Ce-SA-C 3 N 4 , Ce single atoms are coordinated by four N atoms and six O atoms (Ce-N 4 /O 6 ). The cooperation of single-atom Ce-N 4 /O 6 active sites in C 3 N 4 nanosheets tunes the electronic structure and the surface trap states, resulting in accelerated charge transfer/separation and extended lifetime of photoinduced electrons. Meanwhile, the high-coordinated Ce-N 4 /O 6 active sites could promote the production of superoxide radicals ( • O 2 − ) and C = N bond, thus, the optimized single-atom Ce-SA-C 3 N 4 photocatalyst exhibits highly efficient photocatalytic oxidation of amines under visible light irradiation. Furthermore, the fabricated single-atom Ce-SA-C 3 N 4 photocatalysts are applied to split water into hydrogen, producing the maximum hydrogen yield of 33.5 mmol h −1 g −1 . The apparent quantum efficiency for hydrogen evolution achieves 32.6% at 420 nm. This study provides a guideline for rationally designing efficient high-coordinated rare-earth single-atom active sites for efficient solar energy conversion and utilization.