Unraveling the Mechanism of the Zn-Improved Catalytic Activity of Pd-Based Catalysts for Water-Gas Shift Reaction
Unraveling the Mechanism of the Zn-Improved Catalytic Activity of Pd-Based Catalysts for Water-Gas Shift Reaction
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揭示锌提高钯基催化剂水煤气变换反应催化活性的机理
DOI：
10.1021/acs.jpcc.6b07151
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发表时间：
2016
影响因子：
3.7
通讯作者：
Jiang Ruibin
中科院分区：
文献类型：
--
作者：
Hu Jinhui;Guo Wenyue;Liu Zong-Huai;Lu Xiaoqing;Zhu Houyu;Shi Feng;Yan Junqing;Jiang Ruibin
水气转换（WGS）反应在氢经济中起着关键作用。由于反应的放热性质，低温WGS催化剂是非常需要的。zn修饰的pd基催化剂是低温WGS的有希望的候选材料。本文以Pd（111）和PdZn（111）表面为模型，系统研究了添加Zn对WGS催化的影响。Zn的加入使催化剂的电子接受能力减弱，而给电子能力增强。结果表明，电子供体吸附物（H2O、CO、H、顺式cooh、反式cooh和H2）的吸附作用减弱，而电子受体吸附物（O和OH）的吸附作用增强。在Pd（111）和PdZn（111）上发现了相同的最有利反应路径，这是吸附OH辅助羧基脱氢的结合机理。虽然最有利的路径是相同的，但CO吸附的减弱使得CO与OH的结合在Pd（111）上形成顺式cooh到H2O在PdZn（111）上解离的速度决定步骤发生了变化。PdZn（111）上的定速步具有比Pd（111）上的定速步低的能垒。因此，PdZn合金对WGS的促进机制归因于Zn的加入削弱了CO的吸附，从而改变了速率决定步骤。
The water–gas shift (WGS) reaction plays a key role in hydrogen economy. Owing to the exothermic nature of the reaction, low-temperature WGS catalysts are highly desired. Zn-modified Pd-based catalysts are promising candidates for low-temperature WGS. Herein, the effect of Zn addition on the WGS catalysis is systematically studied by using the Pd(111) and PdZn(111) surface as models. Owing to the addition of Zn, the electron-accepting ability of the catalyst is weakened, while the electron-donating ability is increased. As a result, the adsorptions of electron-donor adsorbates, including H2O, CO, H,cis-COOH,trans-COOH, and H2, are weakened, while the adsorptions of electron-acceptor adsorbates, including O and OH, are strengthened. The same most favorable reaction path is found on Pd(111) and PdZn(111), which is the associative mechanism with the carboxyl dehydrogenation assisted by adsorbed OH. Although the most favorable path is the same, the weakening of CO adsorption makes the rate-determining step change from the association of CO and OH formingcis-COOH on Pd(111) to the dissociation of H2O on PdZn(111). The rate-determining step on PdZn(111) has an energy barrier lower than the rate-determining step on Pd(111). The promotion mechanism of the PdZn alloy for WGS is therefore attributed to the fact that the addition of Zn weakens the adsorption of CO and thereby alters the rate-determining step.