Jin Hua, Zhou Hegen, Zhang Yongfan
College of Chemistry and Biology Engineering, Yichun University, Yichun 336000, China.
Engineering Center of Jiangxi University for Lithium Energy, Yichun University, Yichun 336000, China.
Sensors (Basel). 2017 Aug 17;17(8):1898. doi: 10.3390/s17081898.
The mechanism of CO oxidation on the WO₃(001) surface for gas sensing performance has been systematically investigated by means of first principles density functional theory (DFT) calculations. Our results show that the oxidation of CO molecule on the perfect WO₃(001) surface induces the formation of surface oxygen vacancies, which results in an increase of the surface conductance. This defective WO₃(001) surface can be re-oxidized by the O₂ molecules in the atmosphere. During this step, the active O₂ species is generated, accompanied with the obvious charge transfer from the surface to O₂ molecule, and correspondingly, the surface conductivity is reduced. The O₂ species tends to take part in the subsequent reaction with the CO molecule, and after releasing CO₂ molecule, the perfect WO₃(001) surface is finally reproduced. The activation energy barriers and the reaction energies associated with above surface reactions are determined, and from the kinetics viewpoint, the oxidation of CO molecule on the perfect WO₃(001) surface is the rate-limiting step with an activation barrier of about 0.91 eV.
通过第一性原理密度泛函理论（DFT）计算，系统研究了WO₃(001)表面上CO氧化对气敏性能的作用机制。我们的结果表明，CO分子在完美的WO₃(001)表面上的氧化会诱导表面氧空位的形成，这导致表面电导率增加。这种有缺陷的WO₃(001)表面可被大气中的O₂分子重新氧化。在此步骤中，会生成活性O₂物种，同时伴随着从表面到O₂分子的明显电荷转移，相应地，表面电导率降低。O₂物种倾向于参与随后与CO分子的反应，在释放出CO₂分子后，最终重现完美的WO₃(001)表面。确定了与上述表面反应相关的活化能垒和反应能量，从动力学角度来看，CO分子在完美的WO₃(001)表面上的氧化是速率限制步骤，活化能垒约为0.91 eV。
