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Bonding and reactivity at oxide mineral surfaces from model aqueous complexes

机译：模型水性配合物在氧化物矿物表面的键合和反应性

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The kinetic stability of oxide surfaces affects a broad range of physical phenomena, including mineral dissolution and sorp-tion reactions, stable-isotope fractionation, and catalyst support degradation. Our knowledge of the rates of these processes derives mostly from the rates of net mass transfer between the bulk solid and fluid phases. But from such data it is difficult to determine rates of elementary steps that are needed to test theoretical models. Here we determine the rates of oxygen exchange between an aqueous fluid and specific sites on the 'Al_(13)' polyoxocation-AlO_4Al_(12)(OH)_(24)(H_2O)_(12)~(7+)-the structure of which closely resembles the surfaces of some Al-(hydr)oxide minerals in soils and catalyst supports. Extrapolation of these data to 298 K (and near pH 5.3) yields half-lives for oxygen on the complex that range from ～0.6 milliseconds for bound water to 41 seconds and 13 hours for the two distinct, but structurally similar, bridging hydroxyls. This surprisingly large range of labilities (～10~7) indicates that reactivity is very sensitive to molecular structure. Moreover, these results indicate that well chosen aqueous complexes provide important information to relate bonding to reactivity at mineral surfaces.
机译：氧化物表面的动力学稳定性会影响广泛的物理现象，包括矿物溶解和吸附反应，稳定的同位素分馏以及催化剂载体的降解。我们对这些过程速率的了解主要来自于固相和液相之间的净质量转移率。但是从这样的数据很难确定测试理论模型所需的基本步骤的速率。在这里，我们确定了水性流体与'Al_（13）'多氧合-AlO_4Al_（12）（OH）_（24）（H_2O）_（12）〜（7 +）-上的特定位点之间的氧交换速率其结构非常类似于土壤和催化剂载体中某些铝（氢）氧化物矿物的表面。将这些数据外推至298 K（并在pH值5.3附近）时，复合物上的氧气产生半衰期，范围为〜0.6毫秒（结合水）到41秒和13小时（两个截然不同但结构相似的桥连羟基）。如此大的不稳定性（〜10〜7）表明反应性对分子结构非常敏感。此外，这些结果表明，精心选择的水性配合物提供了重要的信息，可将键合与矿物表面的反应性联系起来。

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