Adsorption Energies of Oxygenated Aromatics and Organics on Rhodium and Platinum in Aqueous Phase
Adsorption Energies of Oxygenated Aromatics and Organics on Rhodium and Platinum in Aqueous Phase
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DOI：
10.1021/acscatal.0c00803
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发表时间：
2020-05-01
期刊：
影响因子：
12.9
通讯作者：
Singh, Nirala
中科院分区：
文献类型：
--
作者：
Akinola, James;Barth, Isaiah;Singh, Nirala
准确预测水相中含氧芳香族和有机分子在金属催化剂上的吸附能是具有挑战性的，尽管其与许多催化反应如生物质加氢和加氢脱氧相关。在这里，我们报告了苯酚，苯甲醛，糠醛，苯甲醇，和环己醇的多晶Pt和Rh通过实验等温线和密度泛函理论建模确定的水相吸附的吸附等温线和自由能。所有有机物的实验水溶液吸附热比计算的气相吸附热低50 ~ 250 kJ mol（-1），Rh的降低幅度大于Pt。与气相不同，苯酚和其他芳香族有机物在水相中以类似的强度吸附在Pt和Rh上。苯酚和苯甲醛在Pt和Rh上的相似的水吸附强度解释了它们的可比水相氢化活性，其受Langmuir-Hinshelwood表面反应的速率限制。一个广泛使用的隐式溶剂化模型在很大程度上高估了所有有机物的吸附热与实验测量相比。然而，占有机吸附后，使用键加性模型的置换多个水分子的水溶性罚款给出了一个更接近的实验测量和预测的吸附热之间的协议。这种键加和模型解释了有机物在水相中Pt和Rh上的相似吸附强度是由于水对Rh的粘附力比Pt强，从而抵消了Rh上较强的气相有机物吸附能。本文报道的数据也提供了一个有价值的资源基准方法预测CS/C6有机物在金属表面上的水相吸附能。
Accurately predicting adsorption energies of oxygenated aromatic and organic molecules on metal catalysts in the aqueous phase is challenging despite its relevance to many catalytic reactions such as biomass hydrogenation and hydrodeoxygenation. Here, we report the aqueous-phase adsorption enthalpies and free energies of phenol, benzaldehyde, furfural, benzyl alcohol, and cyclohexanol on polycrystalline Pt and Rh determined via experimental isotherms and density functional theory modeling. The experimental aqueous heats of adsorption for all organics are similar to 50 to 250 kJ mol(-1) lower than calculated gas-phase heats of adsorption, with a larger decrease for Rh compared with that for Pt. Unlike in gas phase, phenol and other aromatic organics adsorb with similar strength on Pt and Rh in aqueous phase. The similar aqueous adsorption strength of phenol and benzaldehyde on Pt and Rh explains their comparable aqueous-phase hydrogenation activities, which are rate-limited by a Langmuir-Hinshelwood surface reaction. A widely used implicit solvation model largely overpredicts the heats of adsorption for all organics compared with experimental measurements. However, accounting for the enthalpic penalty of displacing multiple water molecules upon organic adsorption using a bond-additivity model gives a much closer agreement between experimental measurements and predicted heats of adsorption. This bond-additivity model explains that the similar adsorption strength of organics on Pt and Rh in aqueous phase is due to the stronger adhesion of water to Rh than that on Pt, which offsets the stronger gas-phase organic adsorption energy on Rh. The data reported herein also provides a valuable resource for benchmarking methods for predicting aqueous-phase adsorption energies of CS/C6 organics on metal surfaces.