Boosting CO_(2)photoreduction by synergistic optimization of multiple processes through metal vacancy engineering

The photoreduction of greenhouse gas CO_(2)using photocatalytic technologies not only benefits en-vironmental remediation but also facilitates the production of raw materials for chemicals.Howev-er,the efficiency of CO_(2)photoreduction remains generally low due to the challenging activation of CO_(2)and the limited light absorption and separation of charge.Defect engineering of catalysts rep-resents a pivotal strategy to enhance the photocatalytic activity for CO_(2),with most research on met-al oxide catalysts focusing on the creation of anionic vacancies.The exploration of metal vacancies and their effects,however,is still underexplored.In this study,we prepared an In2O3 catalyst with indium vacancies(VIn)through defect engineering for CO_(2)photoreduction.Experimental and theo-retical calculations results demonstrate that VIn not only facilitate light absorption and charge sepa-ration in the catalyst but also enhance CO_(2)adsorption and reduce the energy barrier for the for-mation of the key intermediate*COOH during CO_(2)reduction.Through metal vacancy engineering,the activity of the catalyst was 7.4 times,reaching an outstanding rate of 841.32μmol g(-1)h^(-1).This work unveils the mechanism of metal vacancies in CO_(2)photoreduction and provides theoretical guidance for the development of novel CO_(2)photoreduction catalysts.

氮掺杂TiO2可见光响应的机理

TiO2是一种良好的光催化剂,具有稳定性好、光效率高和不产生二次污染等特点.但TiO2是宽禁带半导体,只有在紫外光下才具有活性,N掺杂能够明显延长TiO2的吸收光谱至可见光区,但其机理仍有争议.本文介绍了N掺杂TiO2具有可见光活性的几种有争议的机理,包括杂化能带减小理论、杂质能级理论和氧空缺理论,并指出了今后N掺杂TiO2机理的研究方向.

Enhanced ambient ammonia photosynthesis by Mo-doped Bi_(5)O_(7)Br nanosheets with light-switchable oxygen vacancies

The fabrication of efficient catalysts to reduce nitrogen(N_(2))to ammonia(NH3)is a significant challenge for artificial N_(2) fixation under mild conditions.In this work,we demonstrated that the simultaneous introduction of oxygen vacancies(OVs)and Mo dopants into Bi_(5)O_(7)Br nanosheets can significantly increase the activity for photocatalytic N_(2) fixation.The 1 mol% Mo-doped Bi_(5)O_(7)Br nanosheets exhibited an optimal NH_(3) generation rate of 122.9μmol g^(-1) h^(-1) and durable stability,which is attributed to their optimized conduction band position,suitable absorption edge,large number of light-switchable OVs,and improved charge carrier separation.This work provides a promising approach to design photocatalysts with light-switchable OVs for N_(2) reduction to NH_(3) under mild conditions,highlighting the wide application scope of nanostructured BiOBr-based photocatalysts as effective N_(2) fixation systems.

Photoluminescence Properties and Photoactivities of N-doped TiO_2 Nano-powders with Oxygen Vacancies

In order to study the effect mechanism of N-doping on the visible-light photoactivity of TiO2,N-doped and un-doped TiO2 nano-powders were prepared by an acid-catalyzed sol-gel method and characterized by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),electron spin resonance(ESR),UV-Vis diffuse reflection spectra(DRS),and photoluminescence spectra(PL)techniques.Their photoactivities are evaluated by the photocatalytic degradation of methylene blue(MB)in aqueous solution under UV light and visible-light irradiation,respectively.The results reveal that the as-prepared N-doped sample with single anatase exhibits a good visible-light photoactivity,whereas its UV photoactivity decreases slightly,compared with the un-doped sample.The N-doping increases surface hydroxyl groups and forms abundant oxygen vacancies bounding single electrons.The visible-light response of the N-doped sample can be ascribed to a synergetic effect of impurity energy levels due to the substitutional N-doping and defect energy levels owing to the formation of oxygen vacancies.The separation of the photo-generated electron and hole can be promoted by the increase in both oxygen vacancies and surface hydroxyl groups,which are conducive for enhancement of photoactivity.The increase in visible-light photoactivity of the N-doped sample is related with the decrease in its PL spectral intensity in visible-light region.

Effects of Surface Defects on Adsorption of CO and Methyl Groups on Rutile TiO_(2)(110)

The interaction of reactants with catalysts has always been an important subject for catalytic reactions.As a promising catalyst with versatile applications,titania has been intensively studied for decades.In this work we have investigated the role of bridge bonded oxygen vacancy(O_(v))in methyl groups and carbon monoxide(CO)adsorption on rutile TiO_(2)(110)(R-TiO_(2)(110))with the temperature programmed desorption technique.The results show a clear different tendency of the desorption of methyl groups adsorbed on bridge bonded oxygen(O_(b)),and CO molecules on the five coordinate Ti^(4+)sites(Ti_(5c))as the Ovconcentration changes,suggesting that the surface defects may have crucial influence on the absorption of species on different sites of R-TiO_(2)(110).

A highly-efficient oxygen evolution electrode based on defective nickel-iron layered double hydroxide

Exploring efficient and cost-effective electro- catalysts for oxygen evolution reaction （OER） is critical to water splitting. While nickel-iron layered double hydroxide （NiFe LDH） has been long recognized as a promising non- precious electrocatalyst for OER, its intrinsic activity needs further improvement. Herein, we design a highly-efficient oxygen evolution electrode based on defective NiFe LDH na- noarray. By combing the merits of the modulated electronic structure, more exposed active sites, and the conductive elec- trode, the defective NiFe LDH electrocatalysts show a low onset potential of 1.40 V （vs. RHE）. An overpotential of only 200 mV is required for 10 mA cm-2, which is 48 mV lower than that of pristine NiFe-LDH. Density functional theory plus U （DFT＋U） calculations are further employed for the origin of this OER activity enhancement. We find the introduction of oxygen vacancies leads to a lower valance state of Fe and the narrowed bandgap, which means the electrons tend to be ea- sily excited into the conduction band, resulting in the lowered reaction overpotential and enhanced OER performance.