Palladium-based catalysts are among the most efficient for H₂ production via HCOOH (FA) dehydrogenation at near-ambient pressure and temperature. Herein, we show that [PdO/Pd⁰/TiO₂] nanocatalysts bearing a tetragonal PdO nanophase can be optimized for enhanced FA dehydrogenation via engineering of the [PdO:Pd⁰] ratio on the TiO₂ support. We have developed a sequential-deposition flame spray pyrolysis (SD-FSP) technique for deposition of Pd on TiO₂ at a high [PdO:Pd⁰] ratio up to 75%. In addition, we have synthesized low-[PdO:Pd⁰]-ratio catalysts using an oxygen-lean FSP protocol. The SD-FSP-made [PdO/Pd⁰/TiO₂] nanocatalysts with a high [PdO:Pd⁰] ratio >70% can achieve a high H₂ gas production rate of 534 mmol/g of Pd/min that supersedes by >300% the efficiency of [Pd⁰/TiO₂] nanocatalysts with low PdO content. The thermodynamic basis of the role of [PdO:Pd⁰] was investigated by an Arrhenius study, which reveals that the activation energy barrier E_a is decreasing significantly, i.e., up to 50%, upon an increase of the [PdO:Pd⁰] ratio. A reduction of surficial PdO toward Pd⁰, by in situ generated H₂, exerts a strong inhibitory effect on the catalyst. Overall, the present data indicate that both [i] maximization of the [PdO:Pd⁰] ratio and [ii] minimization of PdO reduction during H₂ production are key prerequisites for enhanced FA dehydrogenation by TiO₂-supported/Pd catalysts.

中文翻译：

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火焰喷雾热解法制备PdO / Pd ⁰ / TiO ₂纳米催化剂：PCO / Pd ⁰对HCOOH脱氢制H ₂的协同作用及失活机理的研究

钯基催化剂是在接近环境压力和温度下通过HCOOH（FA）脱氢生产H ₂的最有效方法。在这里，我们表明，可以通过设计TiO ₂载体上的[PdO：Pd ⁰ ]比来优化具有四方PdO纳米相的[PdO / Pd ⁰ / TiO ₂ ]纳米催化剂，以增强FA脱氢。我们已经开发了一种顺序沉积火焰喷雾热解（SD-FSP）技术，用于以高达[ 75％的高[PdO：Pd ⁰ ]比率]在TiO ₂上沉积Pd 。此外，我们已经使用贫氧FSP协议合成了低[[PdO：Pd ⁰ ]-比率的催化剂。SD-FSP制[PdO / Pd ⁰[PdO：Pd ⁰ ]比率> 70％的/ TiO ₂ ]纳米催化剂可以实现534 mmol / g Pd / min的H ₂气体高生产率，而它的效率要高于[Pd ⁰ / TiO 2 ]的300％₂ ]低PdO含量的纳米催化剂。通过Arrhenius研究研究了[PdO：Pd ⁰ ]作用的热力学基础，该研究表明，随着[PdO：Pd ⁰的增加，活化能垒E _a显着降低，即降低了50％。]比率。通过原位生成的H ₂将表面PdO还原为Pd ⁰，对催化剂有很强的抑制作用。总的来说，本数据表明[i] [PdO：Pd ⁰ ]比的最大化和[ii] H ₂生产过程中PdO还原的最小化都是TiO ₂负载的/ Pd催化剂增强FA脱氢的关键前提。