{"title":"Impact of copper on activity, selectivity, and deactivation in the photocatalytic reduction of CO2 over TiO2","authors":"","doi":"10.1016/j.jphotochem.2024.115914","DOIUrl":null,"url":null,"abstract":"<div><p>The photocatalytic reduction of CO<sub>2</sub> to hydrocarbons may be a promising mechanistic route to reduce greenhouse gas CO<sub>2</sub>, convert it into useful products, and limit the direct emission of CO<sub>2</sub>. The photocatalytic reduction of CO<sub>2</sub> is a reaction in which photons activate the photocatalyst by generating reduced and oxidized sites, that are re-oxidized and re-reduced by the reactants. The photocatalytic reduction of CO<sub>2</sub> can produce various products, including CO, formic acid, formaldehyde, methanol, methane, etc.</p><p>Here, the activity/selectivity of produced hydrocarbons in the presence of oxygen on various photocatalysts (TiO<sub>2</sub>, 5 wt%Cu-TiO<sub>2</sub>, 5 wt%Cu-C-TiO<sub>2</sub>) was determined.<!--> <!-->The reaction rate increased with increasing reaction time up to the first half an hour of the reaction but then started to decrease with photocatalysts, indicating photocatalyst deactivation, a rate-limiting step by hydroxyl radicals and adsorption of intermediates on TiO<sub>2</sub>. Carbon deposition as the origin of photocatalyst deactivation was confirmed using the TGA of the spent photocatalyst. Additionally, absorption of intermediates on spent catalysts were confirmed by FTIR. On the other hand, the conversion increased with time when copper was used as a promoter on a TiO<sub>2</sub> compared with TiO<sub>2</sub> due to its larger surface area and having more active sites.</p><p>The photocatalysts were characterized using BET, ICP-OES, XRD, TGA, XPS, Fourier-Transform Infrared Spectroscopy (FTIR), and UV–Vis. The focus of this study was to determine the activity and efficacy of different photocatalysts (TiO<sub>2</sub>, 5 wt%Cu-TiO<sub>2</sub>, 5 wt%Cu-C-TiO<sub>2</sub>) by gas phase measurement, with a particular emphasis on obtaining reproducible data on conversion and selectivity as a function of irradiation time.</p><p>The copper on TiO<sub>2</sub> was found to be more selective towards sodium formate/formic acid with a maximum selectivity of ∼90 % in 4 h and had higher activity (74.3 µmol g<sub>cat</sub><sup>-1 h-1</sup>). A maximum CO with a selectivity of 86 % was found when TiO<sub>2</sub> was used in 4 h.</p><p>Copper transfer electrons on the TiO<sub>2</sub> surface enhance CO<sub>2</sub> adsorption on the catalytic surface and is the reason for having higher valuable product on Cu-C-TiO<sub>2</sub> and Cu-TiO<sub>2</sub> compared with TiO<sub>2</sub>. Carbon in this experiment did not have a role and its effect was negligible.</p></div>","PeriodicalId":16782,"journal":{"name":"Journal of Photochemistry and Photobiology A-chemistry","volume":null,"pages":null},"PeriodicalIF":4.1000,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Photochemistry and Photobiology A-chemistry","FirstCategoryId":"92","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S1010603024004581","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
引用次数: 0
Abstract
The photocatalytic reduction of CO2 to hydrocarbons may be a promising mechanistic route to reduce greenhouse gas CO2, convert it into useful products, and limit the direct emission of CO2. The photocatalytic reduction of CO2 is a reaction in which photons activate the photocatalyst by generating reduced and oxidized sites, that are re-oxidized and re-reduced by the reactants. The photocatalytic reduction of CO2 can produce various products, including CO, formic acid, formaldehyde, methanol, methane, etc.
Here, the activity/selectivity of produced hydrocarbons in the presence of oxygen on various photocatalysts (TiO2, 5 wt%Cu-TiO2, 5 wt%Cu-C-TiO2) was determined. The reaction rate increased with increasing reaction time up to the first half an hour of the reaction but then started to decrease with photocatalysts, indicating photocatalyst deactivation, a rate-limiting step by hydroxyl radicals and adsorption of intermediates on TiO2. Carbon deposition as the origin of photocatalyst deactivation was confirmed using the TGA of the spent photocatalyst. Additionally, absorption of intermediates on spent catalysts were confirmed by FTIR. On the other hand, the conversion increased with time when copper was used as a promoter on a TiO2 compared with TiO2 due to its larger surface area and having more active sites.
The photocatalysts were characterized using BET, ICP-OES, XRD, TGA, XPS, Fourier-Transform Infrared Spectroscopy (FTIR), and UV–Vis. The focus of this study was to determine the activity and efficacy of different photocatalysts (TiO2, 5 wt%Cu-TiO2, 5 wt%Cu-C-TiO2) by gas phase measurement, with a particular emphasis on obtaining reproducible data on conversion and selectivity as a function of irradiation time.
The copper on TiO2 was found to be more selective towards sodium formate/formic acid with a maximum selectivity of ∼90 % in 4 h and had higher activity (74.3 µmol gcat-1 h-1). A maximum CO with a selectivity of 86 % was found when TiO2 was used in 4 h.
Copper transfer electrons on the TiO2 surface enhance CO2 adsorption on the catalytic surface and is the reason for having higher valuable product on Cu-C-TiO2 and Cu-TiO2 compared with TiO2. Carbon in this experiment did not have a role and its effect was negligible.
期刊介绍:
JPPA publishes the results of fundamental studies on all aspects of chemical phenomena induced by interactions between light and molecules/matter of all kinds.
All systems capable of being described at the molecular or integrated multimolecular level are appropriate for the journal. This includes all molecular chemical species as well as biomolecular, supramolecular, polymer and other macromolecular systems, as well as solid state photochemistry. In addition, the journal publishes studies of semiconductor and other photoactive organic and inorganic materials, photocatalysis (organic, inorganic, supramolecular and superconductor).
The scope includes condensed and gas phase photochemistry, as well as synchrotron radiation chemistry. A broad range of processes and techniques in photochemistry are covered such as light induced energy, electron and proton transfer; nonlinear photochemical behavior; mechanistic investigation of photochemical reactions and identification of the products of photochemical reactions; quantum yield determinations and measurements of rate constants for primary and secondary photochemical processes; steady-state and time-resolved emission, ultrafast spectroscopic methods, single molecule spectroscopy, time resolved X-ray diffraction, luminescence microscopy, and scattering spectroscopy applied to photochemistry. Papers in emerging and applied areas such as luminescent sensors, electroluminescence, solar energy conversion, atmospheric photochemistry, environmental remediation, and related photocatalytic chemistry are also welcome.