Atomically Thin Bi₂O₂(OH)_1+x(NO₃)_1–x Nanosheets with Regulated Surface Composition for Enhanced Photocatalytic CO₂ Reduction

Solar-driven CO2 with H2O conversion into valuable chemical fuels has attracted considerable attention. However, the low separation efficiency of photogenerated carriers and deficient surface-active sites on catalysts result in low CO2 reduction activity. Herein, the bulk Bi2O2(OH)(NO3) material was exfoliated to atomically thin nanosheets for shortening the migration distance of photoinduced carriers and enlarging the specific surface area. Photoreduction CO2 test results showed that the CO yield of nanosheets could be enhanced up to nearly six times compared to that of the bulk catalyst. Moreover, a series of ultrathin Bi2O2(OH)1+x(NO3)1–x nanosheets were constructed based on the surface regulation of the OH– concentration on ultrathin nanosheets. The optimized catalyst had an elevated CO yield of 16.7 μmol/g after irradiation for 3 h, about 10 times higher than that of the bulk catalyst. Further theoretical calculations revealed that the superficial NO3– has stronger charge accumulation/depletion behavior with the adjacent Bi atom than surface OH–, conducive to the transfer of photogenerated charge from the bulk phase to the catalyst surface. This work may provide a powerful strategy for the design of a surface-controlled 2D ultrathin photocatalyst for efficient CO2 reduction.