Catalytic consequences of the identity of surface reactive intermediates during direct hydrogen peroxide formation on Pd particles
Catalytic consequences of the identity of surface reactive intermediates during direct hydrogen peroxide formation on Pd particles
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DOI：
10.1016/j.jcat.2019.07.047
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Han Yi-Fan
中科院分区：
文献类型：
--
作者：
Tu Weifeng;Li Xinli;Wang Renquan;Malhi Haripal Singh;Ran Jingyu;Shi Yanling;Han Yi-Fan
H2O2 formation directly from H2 and O2 on Pd particles in water has proven to proceed via two different kinetic regimes defined by the operating H2/O2 ratios using kinetics, isotopic experiments and variation of particle sizes under conditions of kinetic control. These kinetic regimes exhibit different rate equations, kinetic isotope effects and structure sensitivity, while a transition among regimes occurs as the surface reactive intermediates changing from nearly uncovered to saturated with chemisorbed hydrogen (H*) with the increasing of H2/O2 ratio. On nearly bare Pd surfaces, irreversible H2 dissociation limits the rates of H2O2 formation and H2 conversion, thus, rates increase proportionally with H2 pressure but independent of O2 pressure. On H* saturated Pd surfaces, H2 dissociation approaches to chemical equilibrium and the H* mediated HOOH* formation step becomes the sole kinetically relevant step, therefore, rates become insensitive to H2 pressure but are linearly proportional to O2 pressure. The first-order rate coefficients for H2O2 formation become a single-valued function of the operating H2/O2 ratio.
