Enhancing photocatalytic CO 2 reduction by coating an ultrathin Al 2 O 3 layer on oxygen deficient TiO 2 nanorods through atomic layer deposition
Enhancing photocatalytic CO 2 reduction by coating an ultrathin Al 2 O 3 layer on oxygen deficient TiO 2 nanorods through atomic layer deposition
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DOI：
10.1016/j.apsusc.2017.01.267
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发表时间：
2017-05
影响因子：
6.7
通讯作者：
Huilei Zhao;Jiatang Chen;G. Rao;Wei Deng;Ying Li
中科院分区：
文献类型：
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作者：
Huilei Zhao;Jiatang Chen;G. Rao;Wei Deng;Ying Li
本工作成功合成了以{100}晶面为主要晶面的TiO 2纳米棒（ANR），用NaBH 4还原ANR，得到了灰色的氧缺陷TiO 2-x（ReANR）。在ReANR的表面上，使用原子层沉积（ALD）沉积薄的Al 2 O3层，并且Al 2 O3的厚度随ALD循环的次数（1、2、5、10、50、100或200）而变化。高分辨TEM分析表明，Al 2 O3的生长速率为0.25 μ m/周期，XRD分析表明Al 2 O3为非晶态结构。所有合成的光催化剂（ANR，ReANR，和Al 2 O3涂层的ReANR）进行了测试CO2光催化还原在水蒸气的存在下，检测到CO作为主要的还原产物和CH 4作为次要产物。与ANR相比，ReANR的CO生成量增加了50%以上，CH 4生成量增加了10倍以上，这可能是由于氧空位增强了CO2的吸附和活化。通过应用少于5个循环的ALD，Al 2 O3涂层的ReANR比未涂层的ReANR提高了CO和CH 4的总体产量，其中2个循环是最佳的，总体产量比ReANR高出约40%。当ALD循环次数超过5次时，CO和CH 4的生成量均随ALD循环次数的增加而降低。光致发光（PL）分析显示，ReANR上的Al 2 O3（ALD的2个循环）涂层能够降低电荷载流子复合速率，这可能是因为表面态的钝化。另一方面，相对厚的Al 2 O3层可用作绝缘层以阻止电子迁移到催化剂表面。这项工作提供了有价值的见解ALD涂层的光催化剂上的应用，以促进CO2光还原燃料。
In this work, anatase nanorods (ANR) of TiO2with active facet {100} as the major facet were successfully synthesized, and reducing the ANR by NaBH4led to the formation of gray colored oxygen deficient TiO2-x(ReANR). On the surface of ReANR, a thin layer of Al2O3was deposited using atomic layer deposition (ALD), and the thickness of Al2O3varied by the number of ALD cycles (1, 2, 5, 10, 50, 100, or 200). The growth rate of Al2O3was determined to be 0.25 Å per cycle based on high-resolution TEM analysis, and the XRD result showed the amorphous structure of Al2O3. All the synthesized photocatalysts (ANR, ReANR, and Al2O3coated ReANR) were tested for CO2photocatalytic reduction in the presence of water vapor, with CO detected as the major reduction product and CH4as the minor product. Compared with ANR, ReANR had more than 50% higher CO production and more than ten times higher CH4production due to the oxygen vacancies that possibly enhanced CO2adsorption and activation. By applying less than 5 cycles of ALD, the Al2O3coated ReANR had enhanced overall production of CO and CH4than uncoated ReANR, with 2 cycles being the optimum, about 40% higher overall production than ReANR. Whereas, both CO and CH4production decreased with increasing number of ALD cycles when more than 5 cycles were applied. Photoluminescence (PL) analysis showed an ultrathin layer of Al2O3(2 cycles of ALD) coating on the ReANR was able to reduce the charge carrier recombination rate, likely because of the passivation of surface states. On the other hand, a relatively thick layer of Al2O3may act as an insulation layer to prohibit electron migration to the catalyst surface. This work gives valuable insights on the application of ALD coating on photocatalysts to promote CO2photoreduction to fuels.