Internal electric field modulation by copper vacancy concentration of cuprous sulfide nanosheets for enhanced selective CO_(2) photoreduction

Although the internal electric field(IEF)of photocatalysts is acknowledged as a potent driving force for photocharge separation,modulating the IEF intensity to achieve enhanced photocatalytic performances remains a challenge.Herein,cuprous sulfide nanosheets with different Cu vacancy concentration were employed to study IEF modulation and corresponding direct charge transfer.Among the samples,Cu_(1.8)S nanosheets possessed intensified IEF intensity compared with those of Cu_(2)S and Cu_(1.95)S nanosheets,suggesting that an enhanced IEF intensity could be achieved by introducing more Cu vacancies.This intensified IEF of Cu_(1.8)S nanosheets induced numerous photogenerated electrons to migrate to its surface,and the dissociative electrons were then captured by Cu vacancies,resulting in efficient charge separation spatially.In addition,the Cu vacancies on Cu_(1.8)S nanosheets accumulated electrons as active sites to lower the energy barrier of rate-determining step of CO_(2)photoreduction,leading to the selective conversion of CO_(2)to CO.Herein,the manipulation of IEF intensity through Cu vacancy concentration regulation of cuprous sulfide photocatalysts for efficient charge separation has been discussed,providing a scientific strategy to rationally improve photocata lytic performances for solar energy conversion.

Tensile stress enhanced dynamic oxygen vacancies on interlayer stretched Bi_(2)O_(2)CO_(3) as pivotal knobs to promote sustainable selective CO_(2) photoreduction

Surface oxygen vacancies(OVs) with abundant localized electrons on bismuth-oxygen based photocatalysts are proved to have the ability to capture and activate CO_(2).However,the surface OVs are easily filled with oxygen-containing species and destroyed,losing their effects as active sites and hindering the subsequent CO_(2)photoreduction.For realistic and sustainable CO_(2)photoreduction,constructing sustainable and stable surface OVs as active sites on photocatalysts is essential.This work shows the synthesis of interlayer stretched Bi_(2)O_(2)CO_(3) ultrathin nanosheets with tensile stress,which are beneficial to continuously generating light-induced dynamic OVs.With sufficient active sites,excellent,stable,and selective photoreduction of CO_(2)to CO under simulated solar light is achieved.The light-induced OVs can reduce the energy barrier of rate-determining step,resulting in the 100% product selectivity.The results presented herein demonstrate the effect of dynamic OVs induced by interlayer tensile strain on catalysts for the enhanced selective CO_(2)photoreduction process.

Dynamic Active Sites in Bi_(5)O_(7)I Promoted by Surface Tensile Strain Enable Selective Visible Light CO_(2)Photoreduction

Surface defects with abundant localized electrons on bismuth oxyhalide catalysts are proved to have the capability to capture and activate CO_(2).However,bismuth oxyhalide materials are susceptible to photocorrosion,making the surface defects easily deactivated and therefore losing their function as active sites.Construction of deactivation-resistant surface defects on catalyst is essential for stable CO_(2)photoreduction,but is a universal challenge.In this work,the Bi_(5)O_(7)I nanotubes with surface tensile strain are synthesized,which are favorable for the visible light-induced dynamic I defects generation.The CO_(2)molecules absorbed on I defects are constantly reduced by the incoming photogenerated electrons from I-deficient Bi_(5)O_(7)I nanotubes and the successive protonation of CO_(2)molecules is thus highly promoted,realizing the selective CO_(2)conversion process via the route of CO_(2)-COOH^(-)-CO.The efficient and stable photoreduction of CO_(2)into CO with 100%selectivity can be achieved even under visible light(>420 nm)irradiation benefited from the dynamic I defects as active sites.The results presented herein demonstrate the unique action mechanism of light-induced dynamic defects during CO_(2)photoreduction process and provide a new strategy into rational design of deactivation-resistant catalysts for selective CO_(2)photoreduction.

Promoting ring-opening efficiency for suppressing toxic intermediates during photocatalytic toluene degradation via surface oxygen vacancies

Aromatic ring-opening process is well recognized as the rate-determining step for catalytic toluene degradation. In photocatalytic toluene degradation, the toxic intermediates w让h harmful effects may be generated. To clarify the precise reaction mechanism and control the toxic intermediates generation, a closely combined in situ DRIFTS and DFT calculation is utilized to address these important issues. We construct the BiOCl w让h oxygen vacancies (OVs) and reveal the structure of OVs. The defect level caused by oxygen vacancies could promote the light adsorption and charge separation, which further boosts the activation of ring-opening species and enhances the generation process of free radicals. The reaction energy barriers of four possible ring-opening processes on defective BiOCl (OVBOC) are all declined in comparison with perfect BiOCl (BOC). The existence of oxygen vacancies could smooth the ratedetermining step so the ring-opening efficiency of photocatalytic toluene degradation is highly increased. Most importantly, the methyl species would be further oxidized and tend to open the benzene-ring at benzoic acid on BOC while the ring would be broken at the benzyl alcohol on OVBOC. These results indicate that the toluene degradation pathway is shortened via the surface OVs, which enables the production of radicals with high oxidation capability for the accelerated chain scission of the ring-opening intermediates. Finally, the efficiency of the key ring-opening process could be enormously improved and toxic intermediates are effectively restrained. The present work could provide new insights into the design of high-performance photocatalysts for efficient and safe degradation of VOCs in air.

Light-induced halogen defects as dynamic active sites for CO_(2) photoreduction to CO with 100%selectivity

Dynamic defects on halide perovskite materials,caused by ion dissociation and migration under light illumination,typically result in undesirable energy dissipation and limited energy conversion efficiency.However,in this work,we demonstrated that dynamic halogen defects generated by the same process in bismuth oxyhalide(Bi_(5)O_(7)Cl)materials can act as active sites to promote charge separation and photocatalytic efficiency.Mechanistic studies and density functional theory calculations revealed that dynamic Cl defects affected the electronic structure of Bi_(5)O_(7)Cl and photocatalytic CO_(2)reduction process.As active sites,these defects promoted charge transfer,leading to the activation of adsorbed CO_(2)molecules and reduction of the energy barrier of the rate-determining step.Thus,CO_(2)was spontaneously converted into COOH−intermediate and finally reduced to CO with a high efficiency of 108.60μmol g^(−1) and selectivity of 100%after 4-h of CO_(2)photoreduction.This work is highly instructive and valuable to the exploration of dynamic defects on halide-containing materials applied in solar energy conversion.