The use of visible photon fluxes to influence catalytic reactions on metal nanoparticle surfaces has attracted attention based on observations of reaction mechanisms and selectivity not observed under equilibrium heating. These observations suggest that photon fluxes can selectively impact the rates of certain elementary steps, creating nonequilibrium energy distributions among various reaction pathways. However, quantitative studies validating these hypotheses on metal nanoparticle surfaces are lacking. We examine the influence of continuous wave visible photon fluxes on the CO desorption rates from 1 to 2 nm diameter Pt and Pd nanoparticle surfaces supported on γ-Al₂O₃. Temperature-programmed desorption measurements quantified via diffuse reflectance infrared Fourier transform spectroscopy demonstrate that visible photon fluxes significantly enhanced the rate of CO desorption from Pt nanoparticles in a wavelength-dependent manner. 440 nm photons most efficiently promoted CO desorption from Pt nanoparticle surfaces, aligning with the excitation energy for the interfacial electronic transition within the Pt–CO bond. Conversely, visible photon fluxes had no measurable influence on CO desorption rates from Pd nanoparticle surfaces after accounting for photon-induced heating. Density functional theory calculations demonstrate that the Pt–CO bond exhibits a narrower LUMO resonance, stronger coupling between the photoexcitation and forces induced on the metal–C bond, and vibrational energy dissipation that more effectively couples to desorption as compared to Pd–CO. These results demonstrate the specificity photons provide in facilitating chemical reactions on metal nanoparticle surfaces and substantiate the idea that photon fluxes can steer processes and outcomes of catalytic reactions in ways not achievable by equilibrium heating.

中文翻译：

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金属纳米粒子表面的键选择性光化学：Pt 和 Pd 中的 CO 解吸

基于对平衡加热下未观察到的反应机制和选择性的观察，利用可见光子通量影响金属纳米粒子表面的催化反应引起了人们的关注。这些观察结果表明，光子通量可以选择性地影响某些基本步骤的速率，从而在各种反应途径之间产生不平衡的能量分布。然而，缺乏在金属纳米粒子表面验证这些假设的定量研究。我们研究了连续波可见光子通量对负载在 γ-Al ₂ O ₃上的 1 至 2 nm 直径 Pt 和 Pd 纳米粒子表面的 CO 解吸速率的影响。通过漫反射红外傅里叶变换光谱量化的程序升温解吸测量表明，可见光子通量以波长依赖的方式显着提高了 Pt 纳米粒子的 CO 解吸速率。 440 nm 光子最有效地促进 CO 从 Pt 纳米颗粒表面解吸，与 Pt-CO 键内界面电子跃迁的激发能一致。相反，在考虑光子诱导加热后，可见光子通量对 Pd 纳米粒子表面的 CO 解吸速率没有可测量的影响。密度泛函理论计算表明，与 Pd-CO 相比，Pt-CO 键表现出更窄的 LUMO 共振、光激发和金属-C 键上感应力之间更强的耦合，以及更有效地耦合到解吸的振动能量耗散。这些结果证明了光子在促进金属纳米粒子表面的化学反应方面提供的特异性，并证实了光子通量可以以平衡加热无法实现的方式引导催化反应的过程和结果的想法。