Recent research has demonstrated that transition metal nanoparticles on insulating oxide supports can utilize visible photon fluxes to drive a wide range of chemical transformations. These observations have been accompanied by debate on the mechanism of photon-driven catalytic reactions: either equilibrium heating of the catalyst bed or photochemical mechanisms mediated by transient charge transfer to adsorbates. Here, we demonstrate that for ammonia (NH₃) decomposition at low NH₃ pressure (∼0.01 bar) over Ru/Al₂O₃ catalysts, the promotion of NH₃ decomposition rate by visible photon illumination (0–5.5 W cm^–2 of 440–635 nm photons) can be fully explained by photon-induced heating of the catalyst bed. This conclusion is supported by catalytic rate measurements collected under a range of conditions─with and without photo illumination, at different wavelengths, and with varying amounts of cofed H₂─and through the use of a thermocouple placed in the catalyst bed to report the local temperature. Further, we can confirm that CuRu/Al₂O₃ exhibits a non-thermal mechanism in photon-driven NH₃ decomposition. Ultimately, the successful distinction of thermal and non-thermal contributions for low-pressure NH₃ decomposition on Ru/Al₂O₃ appears to be an effective control system to validate experimental approaches for distinguishing between thermal and photochemical contributions in photon-driven catalysis.

中文翻译：

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Ru/Al2O3 上可见光光子介导的 NH3 分解除了加热之外是否还有明显的光化学效应？

最近的研究表明，绝缘氧化物载体上的过渡金属纳米粒子可以利用可见光子通量来驱动各种化学转变。这些观察结果伴随着对光子驱动催化反应机制的争论：催化剂床的平衡加热或由瞬态电荷转移到吸附物介导的光化学机制。在这里，我们证明了在Ru/Al ₂ O ₃催化剂上低 NH _{3压力（∼0.01 bar）下氨（NH 3} ）分解时，可见光子照射（0–5.5 W cm ^–2）可促进 NH ₃分解速率440–635 nm 光子）可以通过催化剂床的光子诱导加热来充分解释。这一结论得到了在一系列条件下（有或没有光照射、不同波长以及不同量的 cofed H ₂ ）收集的催化速率测量的支持，并通过使用放置在催化剂床中的热电偶来报告局部催化速率。温度。此外，我们可以证实CuRu/Al ₂ O _{3在光子驱动的NH 3}分解中表现出非热机制。最终， Ru/Al ₂ O ₃上低压NH ₃分解的热和非热贡献的成功区分似乎是验证在光子驱动催化中区分热和光化学贡献的实验方法的有效控制系统。