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The design of efficient and stable photocatalysts for robust CO2 reduction without sacrifice reagent or extra photosensitizer is still challenging. Herein, a single-atom catalyst of isolated single atom cobalt incorporated into Bi3O4Br atomic layers is successfully prepared. The cobalt single atoms in the Bi3O4Br favors the charge transition, carrier separation, CO2 adsorption and activation. It can lower the CO2 activation energy barrier through stabilizing the COOH* intermediates and tune the rate-limiting step from the formation of adsorbed intermediate COOH* to be CO* desorption. Taking advantage of cobalt single atoms and two-dimensional ultrathin Bi3O4Br atomic layers, the optimized catalyst can perform light-driven CO2 reduction with a selective CO formation rate of 107.1 µmol g−1 h−1, roughly 4 and 32 times higher than that of atomic layer Bi3O4Br and bulk Bi3O4Br, respectively.

Solar-driven reduction of CO2 , which converts inexhaustible solar energy into value-added fuels, has been recognized as a promising sustainable energy conversion technology. However, the overall conversion efficiency is significantly limited by the inefficient charge separation and sluggish interfacial reaction dynamics, which resulted from a lack of sufficient active sites. Herein, Bi12 O17 Cl2 superfine nanotubes with a bilayer thickness of the tube wall are designed to achieve structural distortion for the creation of surface oxygen defects, thus accelerating the carrier migration and facilitating CO2 activation. Without cocatalyst and sacrificing reagent, Bi12 O17 Cl2 nanotubes deliver high selectivity CO evolution rate of 48.6 μmol g-1 h-1 in water (16.8 times than of bulk Bi12 O17 Cl2 ), while maintaining stability even after 12 h of testing. This paves the way to design efficient photocatalysts with collaborative optimizing charge separation and CO2 activation towards CO2 photoreduction.

Photocatalytic CO2 reduction has been regarded as an appealing pathway for CO2 conversion to hydrocarbon fuels. To boost the CO2 photoreduction performance, developing suitable cocatalyst on the photocatalysts is an efficient strategy. Herein, Co2N is employed as novel noble-metal-free cocatalyst to promote the CO2 photoreduction performance of BiOBr ultrathin nanosheets. The optimal Co2N/BiOBr delivers a high selectivity CO formation rate of 67.8 µmol g−1 h−1 in pure water without sacrificial reagent or extra photosensitizer, roughly 6 times higher than BiOBr. Co2N can create strong electronic interactions with BiOBr, steering the electron transfer from BiOBr, across the interface to metallic Co2N and finally to the surface. Apart from the charge separation steering, the activation energy barrier can be lowered on Co2N surface via stabilize COOH* intermediates, tuning the rate-limiting step from the formation of COOH* on BiOBr to the formation of CO* on Co2N, jointly optimize the CO2 photoreduction activity. This strategy affords an accessible pathway for designing cocatalysts for efficient CO2 photoreduction.

Photocatalytic CO2 reduction suffers from the weakness of high energy barrier, low efficiency and poor selectivity. Exploring effective strategy to enhance the adsorption and activation behavior of CO2 molecules is an alternative approach to boost CO2 photoreduction performance. In this work, abundant oxygen vacancies (VO) are introduced onto Bi2Sn2O7 nanoparticles (NPs) by decreasing their size down to about 4 nm. The VO mediated NPs exhibit a tremendous 8.1 times enhanced performance than the bulk counterpart towards CO2-to−CO conversion in pure water. This is attributed to fast charge diffusion and abundant Vo for effective CO2 adsorption and activation in the ultra-small nanoparticles. The VO mediated Bi2Sn2O7 NPs have electron back donation nature and optimized electronic structure for effectively activating CO2, which were demonstrated by density functional theory calculations. During the reduction process, the Vo can effeciently stabilize the COOH* intermediates, and also lower the energy barrier of CO desorption determining step.