Kinetic Effect of Surface Chemisorbed Oxygen on Platinum-Catalyzed Hydrogen Peroxide Decomposition
Kinetic Effect of Surface Chemisorbed Oxygen on Platinum-Catalyzed Hydrogen Peroxide Decomposition
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DOI：
10.1007/s10562-020-03280-2
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发表时间：
2020-06-06
影响因子：
2.8
通讯作者：
Michel, F. Marc
中科院分区：
文献类型：
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作者：
Serra-Maia, Rui;Rimstidt, J. Donald;Michel, F. Marc
由铂纳米催化剂催化的H2 O2化学分解为H2O和O-2在许多技术中是重要的，例如蒸汽推进、生物传感器、燃料电池和合成化学。表面化学吸附的氧强烈地影响该反应的动力学。然而，这种表面物种的影响还没有被量化的上下文中的反应机制。本研究测定了铂纳米催化剂上H2 O2分解的基元反应步骤的速率常数。为此，对具有不同表面化学吸附氧（Pt（O））丰度的样品进行了过氧化氢分解率测量分析。反应级数在表面Pt（O）丰度方面为0.83，这表明H2 O2分解速率的近一级效应。该结果与涉及两个循环步骤的H2 O2在铂上分解的反应机理一致，其中步骤1是限速步骤。步骤1 Pt + H2 O2->（k=0.0028）H2O + Pt（O）步骤2 Pt + H2 O2->（k=0.038）Pt + H2O + H2O/k= 0.037总2H（2）O（2）->（k=0.037）O-2 + 2 H（2）O在反应温度T = 295 K时，步骤2的速率常数（k）比步骤1的速率常数（k）高14倍。这与步骤1的4.4倍大的活化能一致。在具有更多表面Pt（O）位点的样品上，反应速率最初更快，因为这些位点在反应的第一循环中通过步骤2分解H2 O2。在较高温度下，步骤1和步骤2的相对速率变小。在这项研究中提出的方法可用于确定许多其他化学反应的中间反应步骤的速率常数，这些化学反应对于许多科学和技术应用是重要的。[图形]。
The chemical decomposition of H2O2 to H2O and O-2 catalyzed by platinum nanocatalysts is important in many technologies such as steam propulsion, biosensors, fuel cells, and synthetic chemistry. Surface chemisorbed oxygen strongly impacts the kinetics of this reaction. However, the effect of this surface species has not been quantified in the context of the reaction mechanism. This study determined the rate constants of the elementary reaction steps of H2O2 decomposition on platinum nanocatalysts. For that, hydrogen peroxide decomposition rate measurements were analyzed on samples with variable surface chemisorbed oxygen (Pt(O)) abundance. The order of reaction in terms of surface Pt(O) abundance is 0.83, which indicates a nearly first order effect on the rate of H2O2 decomposition. This result is consistent with a reaction mechanism for H2O2 decomposition on platinum that involves two cyclic steps, where step 1 is the rate limiting step.Step 1 Pt + H2O2 ->(k=0.0028) H2O + Pt(O)Step 2 Pt + H2O2 ->(k=0.038) Pt + H2O + H2O/k=0.037Overall 2H(2)O(2)->(k=0.037) O-2 + 2H(2)OThe rate constant (k) of step 2 is 14 times higher than that of step 1 at a reaction temperature T = 295 K. This is consistent with a 4.4 time larger activation energy for step 1. Reaction rates are initially faster on samples with more surface Pt(O) sites because these sites decompose H2O2 through step 2 in the first cycle of the reaction. The relative rates of step 1 and step 2 become smaller at higher temperature. The method presented in this study can be used for determining the rate constants of the intermediate reaction steps of many other chemical reactions that are important for numerous scientific and technological applications.[GRAPHICS].