Lanthanide single atom modified catalysts are rarely reported because the roles of lanthanide in photocatalysis are difficult to explain clearly. Based on the construction of Er single atom modified black phosphorus/SnNb2O6 (BP/SNO) heterojunctions, the synergistic effect of 4f levels of Er and heterostructures was studied by combining steady-state, transient, and ultrafast spectral analysis techniques with DFT theoretical calculations. According to the Judd-Ofelt theory of lanthanide ions, the CO2 photoreduction test under single wavelength excitation verifies that the 4F7/2/2H11/2 → 4I15/2 emissions of Er in BPEr/SNOEr can be more easily absorbed by SNO and BP, further proving the role of the 4f levels. As a result, the CO and CH4 yields of BPEr/SNOEr-10 under visible light irradiation are 10.7 and 10.1 times higher than those of pure BP, respectively, and 3.4 and 1.5 times higher than those of SNO. The results of DFT calculations show that the Er single atoms can cause surface reconstruction, regulate the active sites of BP, and reduce the energy change value in the key steps (CO2* + H+ + e- → COOH* and COOH* → CO* + H2O). This work provides novel insights into the design of lanthanide single atom photocatalysts for CO2 reduction.
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