Pt助剂的尺寸调控及其对光催化CO2制CH4性能的影响

Size regulation of Pt cocatalysts and its effect on the performance of photocatalytic CO2 transformation to CH4

  • 摘要: 铂是光催化二氧化碳(CO2)还原制甲烷(CH4)最有效的助催化剂之一,但仍面临CO2还原速率和CH4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/TiO2催化剂并将其用于光催化还原CO2制CH4反应。Pt/TiO2催化CO2还原速率和CH4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(71.9 μmol/(g·h))且没有检测到H2的生成;烷烃产物(CH4、C2H6、C3H8)选择性为100%,CH4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、CO2-TPD、H2O-TPD、H2-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CO2能力、合适的活化H2O能力和较高的氢脱附温度,使H2O活化生成活性氢速率与CO2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CO2还原催化剂具有重要参考价值。

     

    Abstract: Platinum is one of the most efficient cocatalysts for photocatalytic reduction of carbon dioxide (CO2) to methane (CH4), but it still suffers from low CO2 reduction rate and low selectivity of CH4. In this study, Pt/TiO2 catalysts with adjustable Pt particle size (0.55−1.80 nm) were prepared by atomic layer deposition (ALD) and used for photocatalytic reduction of CO2 to CH4. The CH4 yield and selectivity of the Pt/TiO2 catalysts showed a volcanic variation trend with the increase of Pt particle size. The 10Pt/TiO2 with Pt particle size of 1.35 nm exhibit the highest methane yield (71.9 μmol/(g·h)). Especially, a high electron-based selectivity of 81.69% for CH4 (product-based selectivity of 90.20%), and 100% for hydrocarbons (CH4, C2H6 and C3H8) are achieved, no H2 formation was detected. The CO-DRIFTS, XPS, CO2-TPD, H2O-TPD, and H2-TPD characterizations suggest that the 10Pt/TiO2 exhibited optimal CO2 adsorption/activation capacity, suitable H2O activation capacity, and higher hydrogen desorption temperature, making the generation rate of active hydrogen species from H2O matches their consumption rate for CO2 hydrogenation. This study opens an avenue for rationally designing highly efficient and selective photocatalysts for photocatalytic CO2 reduction.

     

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