Ag/Ag_2WO_4等离子体共振催化剂可见光催化还原CO_2

Ag/Ag_2WO_4 Plasmonic Catalyst for Photocatalytic Reduction of CO_2 under Visible Light

转化CO_2为有机组分是缓解全球变暖和保障持续能源供给的有效方法之一.采用简易的离子交换结合水合肼还原法制备了一系列不同晶相Ag_2WO_4载银(Ag/Ag_2WO_4)的等离子共振光催化剂,并用X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜-能量色散X射线光谱(SEM-EDS)、紫外-可见(UV-ViS)吸收光谱和比表面积测试对催化剂进行了表征.较之Ag_2WO_4,Ag/Ag_2WO_4在可见光催化还原CO_2生成CH_4时显示了明显提高的量子产率(QY)、能量投入产出比(EROEI)、转换数(TON),就Ag/α-Ag_2WO_4,Ag/β-Ag_2WO_4和Ag/γ-Ag_2WO_4而言,最佳催化剂为Ag/β-Ag_2WO_4,其实际最佳Ag:Ag_2WO_4摩尔比为4:96,该催化剂还原CO_2为CH_4的QY、EROEI、TON和拟一级反应速率常数分别为0.145%、0.067%、9.61和1.96×10^(-6)min^(-1).此外制备的等离子共振Ag/Ag_2WO_4光催化剂在可见光辐照下进行循环反应仍能保持稳定性.局域表面等离子共振效应是强化Ag/Ag_2WO_4光催化剂活性和稳定性的主要原因.

The conversion of CO2 into organic compounds is a promising method to mitigate global warming and assist in sustaining energy resources. A series of plasmonic photocatalysts, comprised of Ag supported on Ag2WO, （Ag/Ag2WO4） with different crystalline phases, are fabricated by a facile ion-exchange method and subsequent reduction with hydrazine hydrate. The catalysts are characterized using X-ray diffraction （XRD） spectroscopy, X-ray photoelectron spectroscopy （XPS）, scanning electron microscopy with energy-dispersive X-ray spectroscopy （SEM-EDS）, UV-Vis absorption spectroscopy, and Brunauer-Emmett-Teller analyses. Compared with Ag2WO4, the Ag/Ag2WO,exhibits a markedly improved quantum yield （QY）, energy returned on energy invested （EROEI）, and turnover number （TON） for CO2 reduction to CH4 under visible-light irradiation. Among Ag/cr-Ag2WO,, Ag/β-Ag2WO,, and Ag/y-Ag2WO, catalysts, the highest activity for CO2 photoreduction to CH, is obtained for Ag/β-Ag2WO, with an actual molar composition of 4% Ag and 96% Ag2WO4. Correspondingly the QY, EROEI, TON, and pseudo first-order rate constant are 0.145%, 0.067%, 9.61, and 1.96 × 10-6 min-1, respectively. Moreover, the plasmonic Ag/Ag2WO, photocatalysts are stable after repeated reaction cycles under visible-light irradiation. It is proposed that the localized surface plasma resonance effect of surface- deposited Ag contributed to the enhanced activities and stabilities of the Ag/Ag2WO4 photocatalysts.