Explaining the structure sensitivity of Pt and Rh for aqueous-phase hydrogenation of phenol
Explaining the structure sensitivity of Pt and Rh for aqueous-phase hydrogenation of phenol
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DOI：
10.1063/5.0085298
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发表时间：
2022-03-14
影响因子：
4.4
通讯作者：
Goldsmith, Bryan R.
中科院分区：
文献类型：
--
作者：
Barth, Isaiah;Akinola, James;Goldsmith, Bryan R.
苯酚是了解生物质热催化（TCH）和电催化加氢（ECH）制生物燃料的重要模型化合物。虽然Pt和Rh是研究最多的水相苯酚加氢催化剂，但某些方面对ECH和TCH有活性的原因尚不完全清楚。在此，我们确定了Pt和Rh催化剂对苯酚水相加氢的活性方面，并解释了Pt和Rh纳米颗粒的大小依赖的活性趋势的起源。通过拟合动力学数据，提取了Pt和Rh纳米颗粒在碳上的活性位点对苯酚的吸附能，表明活性位点对苯酚的吸附能力较弱。基于密度泛函理论模型和平均场微动力学模拟，我们预测Pt（111）和Rh（111）台阶上苯酚加氢生成环己酮的周转率（tof）高于（221）台阶上的周转率。（111）梯田的活性较高是由于其活化能较低，对苯酚的吸附较弱，阻止了苯酚的高覆盖抑制氢的吸附。我们测量到，相对于可逆氢电极，在298 K和-0.1 V下，Rh纳米颗粒直径从2 nm增加到10 nm，苯酚的ECH的TOF增加，在质量上与先前报道的Pt纳米颗粒相匹配。随着Pt和Rh纳米颗粒直径的增加，实验tof的增加是由于较大颗粒上的阶地比例较大。这些发现阐明了Pt和Rh对苯酚加氢反应的结构敏感性和活性位点，并将为生物油加氢催化剂的设计提供信息。由AIP出版社独家授权出版。
Phenol is an important model compound to understand the thermocatalytic (TCH) and electrocatalytic hydrogenation (ECH) of biomass to biofuels. Although Pt and Rh are among the most studied catalysts for aqueous-phase phenol hydrogenation, the reason why certain facets are active for ECH and TCH is not fully understood. Herein, we identify the active facet of Pt and Rh catalysts for aqueous-phase hydrogenation of phenol and explain the origin of the size-dependent activity trends of Pt and Rh nanoparticles. Phenol adsorption energies extracted on the active sites of Pt and Rh nanoparticles on carbon by fitting kinetic data show that the active sites adsorb phenol weakly. We predict that the turnover frequencies (TOFs) for the hydrogenation of phenol to cyclohexanone on Pt(111) and Rh(111) terraces are higher than those on (221) stepped facets based on density functional theory modeling and mean-field microkinetic simulations. The higher activities of the (111) terraces are due to lower activation energies and weaker phenol adsorption, preventing high coverages of phenol from inhibiting hydrogen adsorption. We measure that the TOF for ECH of phenol increases as the Rh nanoparticle diameter increases from 2 to 10 nm at 298 K and -0.1 V vs the reversible hydrogen electrode, qualitatively matching prior reports for Pt nanoparticles. The increase in experimental TOFs as Pt and Rh nanoparticle diameters increase is due to a larger fraction of terraces on larger particles. These findings clarify the structure sensitivity and active site of Pt and Rh for the hydrogenation of phenol and will inform the catalyst design for the hydrogenation of bio-oils. Published under an exclusive license by AIP Publishing.