Koch Christopher J, Naglic Jennifer, Kearney Logan, Clairmonte Daniel, Rai Binod, Lauterbach Jochen, Angelette Lucas M, Guin Tyler
Hydrogen Isotope Processing Science, Savannah River National Laboratory, Aiken, South Carolina 29803, United States.
Chemical Sciences Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, United States.
ACS Omega. 2025 Apr 10;10(15):15243-15249. doi: 10.1021/acsomega.4c09968. eCollection 2025 Apr 22.
Ammonia is a promising candidate as a liquid hydrogen energy storage medium, but it requires catalytic decomposition (ammonia cracking) to regenerate hydrogen. Recently developed trimetallic ruthenium-potassium-promoter (RuKM) ammonia decomposition catalysts have exceptionally low ammonia decomposition temperatures, able to perform the decomposition as low as 250 °C, which is significantly lower than other known catalysts that require temperatures above 500 °C. However, the effects of the RuKM precursor on the catalytic activity have not been investigated. We report the observed differences of 3% ruthenium/12% potassium/1% yttrium (RuKY) catalysts on γ-alumina synthesized from chloride-, nitrate-, and acetate-based precursors. Catalysts synthesized from chloride-based precursors demonstrated the lowest ammonia decomposition catalytic activity at lower reaction temperatures. In contrast, those synthesized from nitrate-based precursors demonstrated the highest yield, despite similar metal loading. This difference in reactivity is most apparent between 250 and 400 °C, as the conversion rates of the catalysts synthesized with chloride-free precursors are up to 50% greater than those synthesized with chloride precursors. The observed differences in catalytic activity were much less apparent above 450 °C. The observed activation energies of the catalysts were independent of the precursor utilized, despite the difference in catalytic activity, suggesting that the active site composition was the same for all catalysts. These results suggest a pathway to improved ammonia cracking catalysts by tailoring the precursor used in the synthesis.
氨是一种很有前景的液态氢储能介质候选物，但它需要催化分解（氨裂解）来再生氢气。最近开发的三金属钌 - 钾促进剂（RuKM）氨分解催化剂具有极低的氨分解温度，能够在低至250°C的温度下进行分解，这明显低于其他已知需要500°C以上温度的催化剂。然而，RuKM前驱体对催化活性的影响尚未得到研究。我们报告了由基于氯化物、硝酸盐和乙酸盐的前驱体制备的负载3%钌/12%钾/1%钇（RuKY）的γ - 氧化铝催化剂的观察差异。由氯化物基前驱体制备的催化剂在较低反应温度下表现出最低的氨分解催化活性。相比之下，由硝酸盐基前驱体制备的催化剂尽管金属负载量相似，但产率最高。这种反应性差异在250至400°C之间最为明显，因为由无氯前驱体制备的催化剂的转化率比由氯化物前驱体制备的催化剂高出50%。在450°C以上，观察到的催化活性差异不太明显。尽管催化活性存在差异，但观察到的催化剂活化能与所使用的前驱体无关，这表明所有催化剂的活性位点组成相同。这些结果表明了一条通过调整合成中使用的前驱体来改进氨裂解催化剂的途径。
