氢能因清洁高效、可再生等优点，被视为21世纪最具发展潜力的清洁能源。水煤气变换反应是工业上常用的反应，在将CO废气回收利用的同时也是一种重要的制氢手段，具有治理环境和节能减排的双重优点。α-MoC作为一种催化载体，显示出优异的特性。Pd,Ni,Pt基催化剂是水煤气变换反应常用的催化剂。为了进一步了解α-MoC载体在水煤气变换反应中的作用和其负载不同金属时的催化性能，密度泛函理论和动力学蒙特卡洛方法考察了Ni4/α-MoC(111)，Pd4/α-MoC(111)和Pt4/α-MoC(111)上的反应机理和活性。研究结果显示，在Ni4/α-MoC(111)和Pd4/α-MoC(111)，水煤气变换反应为氧化还原路径:CO直接与H2O分解产生的氧结合，生成CO2;在Pt4/α-MoC(111)催化剂上，水煤气变换反应通过羧酸盐路径发生:CO与H2O分解产生的羟基结合，生成羧酸盐中间体，最后分解成CO2。Ni4/α-MoC(111)和Pd4/α-MoC(111)催化剂上水煤气变换反应的能垒较高，因此催化剂活性和H2的转换频率较低。Pt4/α-MoC(111)催化剂上，由于CO的强稳定性导致活性位点被其覆盖，反应活性较低;随着反应温度的升高，CO的脱附能降低，催化活性随之增高。总体来说，标准大气压下，反应温度在400~500 K内，H2O与CO的物质的量之比为1时，Pt4/α-MoC (111)催化剂H2的转换频率最高。相比Pt/Al2O3和Pt/TiO2催化剂，Pt/α-MoC是最佳的水煤气变换反应催化剂。

Hydrogen energy is regarded as the most promising clean energy in the 21st century due to its advantages of clean,efficient and renewable.Water-gas shift (WGS) reaction is a commonly employed reaction in the industry.It is also an important means of hydrogen production while recycling CO waste gas.Besides,it has the dual advantages of environmental governance and energy saving and emission reduction.As a catalyst support,α-MOC shows excellent properties.Pd,Ni and Pt based catalysts are commonly used in the WGS reaction.In order to further understand the role of α-MoC support in the WGS reaction and its catalytic performance under different metal loadings,the reaction mechanism and activities of Ni4/α-MoC (111),Pd4/α-MoC (111) and Pt4/α-MoC (111) were investigated by using density function theory (DFT) and kinetic Monte Carlo (KMC) simulation.The results show that the WGS reaction on Ni4/α-MoC (111) and Pd4/α-MoC (111) is redox mechanism,of which *CO combines with atomic oxygen from water decomposition to generate CO2;the WGS reaction on Pt4/α-MoC (111) occurs via the carboxyl pathway,of which carboxylate intermediate is formation from *CO reacts with *OH produced from water decomposition.Ni4/α-MoC (111) and Pd4/α-MoC (111) show low catalytic activity because of the high energy barrier.At a low temperature,Pt4/α-MoC (111) also shows low a catalytic activity due to strong stability of *CO,of which the active sites are covered by *CO.With the reaction temperature increasing,the desorption energy of *CO decreases,and the catalytic activity increases.At the reaction temperature varied from 400 to 500 K,Pt4/α-MoC (111) shows the highest H2 turnover frequency at 1 atm with a CO:H2O ratio of 1.Compared with the Pt/Al2O3 and Pt/TiO2,Pt/α-MoC shows the highest H2 turnover frequency.

1 计算方法和模型

2 结果与讨论

3 结论