Pt助剂的尺寸调控及其对光催化CO_(2)制CH_(4)性能的影响

Size regulation of Pt cocatalysts and its effect on the performance of photocatalytic CO_(2)transformation to CH_(4)

铂是光催化二氧化碳(CO_(2))还原制甲烷(CH_(4))最有效的助催化剂之一,但仍面临CO_(2)还原速率和CH_(4)选择性低的难题。本研究利用原子层沉积(ALD)制备了Pt颗粒尺寸可调(0.55-1.80 nm)的Pt/TiO_(2)催化剂并将其用于光催化还原CO_(2)制CH_(4)反应。Pt/TiO_(2)催化CO_(2)还原速率和CH_(4)选择性随Pt颗粒尺寸增加呈现出先增加后降低的火山型趋势,其中,Pt颗粒尺寸为1.35 nm时,催化剂的甲烷收率最高(71.9μmol/(g·h))且没有检测到H_(2)的生成;烷烃产物(CH_(4)、C_(2)H_(6)、C_(3)H_(8))选择性为100%,CH_(4)的电子选择性和碳基产物选择性分别高达81.69%和90.20%。CO-DRIFTS、XPS、CO_(2)-TPD、H_(2)O-TPD、H_(2)-TPD等分析结果表明,Pt颗粒尺寸为1.35 nm时,具有最优的活化CO_(2)能力、合适的活化H_(2)O能力和较高的氢脱附温度,使H_(2)O活化生成活性氢速率与CO_(2)还原消耗活性氢速率相匹配,展示出最佳性能。本研究对开发高活性和高选择性的光催化CO_(2)还原催化剂具有重要参考价值。

Platinum is one of the most efficient cocatalysts for photocatalytic reduction of carbon dioxide(CO_(2))to methane(CH_(4)),but it still suffers from low CO_(2)reduction rate and low selectivity of CH_(4).In this study,Pt/TiO_(2)catalysts with adjustable Pt particle size(0.55-1.80 nm)were prepared by atomic layer deposition(ALD)and used for photocatalytic reduction of CO_(2)to CH_(4).The CH_(4)yield and selectivity of the Pt/TiO_(2)catalysts showed a volcanic variation trend with the increase of Pt particle size.The 10Pt/TiO_(2)with Pt particle size of 1.35 nm exhibit the highest methane yield(71.9μmol/(g·h)).Especially,a high electron-based selectivity of 81.69%for CH_(4)(product-based selectivity of 90.20%),and 100%for hydrocarbons(CH_(4),C_(2)H_(6) and C_(3)H_(8))are achieved,no H_(2)formation was detected.The CO-DRIFTS,XPS,CO_(2)-TPD,H_(2)O-TPD,and H_(2)-TPD characterizations suggest that the 10Pt/TiO_(2)exhibited optimal CO_(2)adsorption/activation capacity,suitable H_(2)O activation capacity,and higher hydrogen desorption temperature,making the generation rate of active hydrogen species from H_(2)O matches their consumption rate for CO_(2)hydrogenation.This study opens an avenue for rationally designing highly efficient and selective photocatalysts for photocatalytic CO_(2)reduction.