Bi₂O₃ as a Promoter for Cu/TiO₂ Photocatalysts for the Selective Conversion of Carbon Dioxide into Methane

Abstract

[a] As ignificantly enhancedg as-phase photocatalytic conversion of carbon dioxide into methane on Cu/TiO 2 nanoparticles upon introducing Bi 2 O 3 as ap romoter in the vicinity of Cu was observed. The maximum rate of CH 4 generation of 11.90 mmol g À1 h À1 recorded in the case of Cu-Bi 2 O 3 /TiO 2 is approximately one order of magnitude higher than that obtained with Cu/TiO 2 nanoparticles. The enhanced performance was attributed to facilitated migration of CO* from Cu to the Bi 2 O 3 surface.The increasing concentrationo fa tmospheric carbond ioxide (CO 2 )i saconcern, as the relatively high heat capacity of carbon dioxide is consideredt or esulti na ccelerated global warming. [1][2][3] As am eanst om itigate issues originating from elevated CO 2 concentrations, many researchers have pursued methods for the direct reduction of CO 2 to hydrocarbon fuels by utilizing solar energy or electrochemical potential. [4,5] Highly efficient photocatalytic conversion of CO 2 demands the design of photocatalystst hat offer strong adhesion to CO 2 and the reaction intermediates. [6,7] Of particulari mportance is the design of metal cocatalysts that can draw photogenerated electrons from the semiconductor and enhancea dsorption of CO 2 and intermediate species, forexample, CO*,ont he surface. [8][9][10] Despite significant progress in the electrochemical reduction of CO 2 , [11][12][13][14][15][16] high-activitya nd high-selectivity photocatalysts are still being pursued. Onen otable discussion in the fieldo fe lectrocatalytic conversion involves the binding strengtho fC Ot o the catalystsurface, in asense that the adsorption strength determines the activity and selectivityo fC O 2 reduction. [17,18] For example, Kuhl et al. reported that CO is apredominant product for cases in which Au, Ag, and Zn, which bind to CO weakly, are used, whereas hydrogen is the main product for cases in which Pt, Ni, and Fe, which are strongC Oa dsorbers, are used.[11] The use of Cu, whichhas moderate CO binding, results in the production of hydrocarbons. Notably,i th as been suggested that bimetallic alloy catalysts, such as AuCu and AuPt, give rise to the production of hydrocarbons, asa lloyinge nables control of the CO binding strength. [18,19] However,t hese tacticst od esign metal cocatalysts have not seen great success in the study of photocatalysis.In the case of electrocatalysis, faradaic efficiency is relatively high for hydrocarbonsi fC ui su sed as am etal cocatalyst. In contrast, photocatalytic conversion on Cu results in the productiono fC O. [20,21] To address the issue of selectivity,b inary alloy cocatalysts andc ore-shell structuresh ave been utilized and investigated. [22][23][24] However,the mechanism by which intermediate speciesi nteract with the surfacer emains unclear, which ultimately hinders progress in the design of high-efficiency photocatalysts.In this study,w ei nvestigate the role of Bi 2 O 3 as ap romoter for Cu cocatalysts anchored on TiO 2 nanoparticles. The ability to tune the composition ratio betweenB i 2 ...

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Multi-Layered Mesoporous TiO2 Thin Films: Photoelectrodes with Improved Activity and Stability

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Copper‐Decorated Microsized Nanoporous Titanium Dioxide Photocatalysts for Carbon Dioxide Reduction by Water

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