Dehydrogenation of ammonia on free-standing and epitaxial hexagonal boron nitride.
Dehydrogenation of ammonia on free-standing and epitaxial hexagonal boron nitride.
复制标题
氨在独立外延六方氮化硼上脱氢。
DOI：
10.1039/d2cp01392d
复制
发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Payne AJR
中科院分区：
文献类型：
--
作者：
Payne AJR
我们报道了一种热力学上可行的以hBN为催化剂由NH3生成H2的机理。二维催化剂具有特殊的表面积，具有独特的热和电子性质，适合于催化。无金属的二维催化剂是非常理想的材料，它比普遍使用的贵金属和过渡金属催化剂更具可持续性。本文利用密度泛函理论（DFT）计算，证明了无金属六方氮化硼（hBN）是一种有效的贵金属催化剂，可用于产生具有硼氮价差（VBN）的氨的H2via反应。结果表明，氨的分解在单层hBN上进行，活化能势垒为0.52 eV。此外，我们还研究了氨与外延生长的hBN在Ru（0001）衬底上的反应，我们观察到类似的NH3分解能垒（0.61 eV），但更容易的H2结合解吸能垒（0.69 eV vs 5.89 eV）。而独立的单分子膜则通过3.36 eV的扩散过程生成H2。对反应路径上的电子密度和电荷分布进行了详细的分析，以合理地解释底物对催化反应的影响。
We report a thermodynamically feasible mechanism for producing H2 from NH3 using hBN as a catalyst. 2D catalysts have exceptional surface areas with unique thermal and electronic properties suited for catalysis. Metal-free, 2D catalysts, are highly desirable materials that can be more sustainable than the ubiquitously employed precious and transition metal-based catalysts. Here, using density functional theory (DFT) calculations, we demonstrate that metal-free hexagonal boron nitride (hBN) is a valid alternative to precious metal catalysts for producing H2via reaction of ammonia with a boron and nitrogen divacancy (VBN). Our results show that the decomposition of ammonia proceeds on monolayer hBN with an activation energy barrier of 0.52 eV. Furthermore, the reaction of ammonia with epitaxially grown hBN on a Ru(0001) substrate was investigated, and we observed similar NH3 decomposition energy barriers (0.61 eV), but a much more facile H2 associative desorption barrier (0.69 eV vs 5.89 eV). H2 generation from the free-standing monolayer would instead occur through a diffusion process with an energy barrier of 3.36 eV. A detailed analysis of the electron density and charge distribution along the reaction pathways was carried out to rationalise the substrate effects on the catalytic reaction.