Cao Yuehan, Yang Yuantao, Yu Wang, Li Gao, Rao Zhiqiang, Huang Zeai, Wang Fang, Yuan Chengdong, Zhou Ying
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China.
Institute of Carbon Neutrality, School of New Energy and Materials, Southwest Petroleum University, Chengdu 610500, China.
ACS Appl Mater Interfaces. 2022 Mar 23;14(11):13344-13351. doi: 10.1021/acsami.1c25203. Epub 2022 Mar 14.
The key scientific challenge for methane (CH) direct conversion to methanol (CHOH) is considered to be the prevention of overoxidation of target products, which is restrained by the difficulty in the well-controlled process of selective dehydrogenation. Herein, we take single noble metal atom-anchored hexagonal boron nitride nanosheets with B vacancies (M/BN) as the model materials and first propose that the dehydrogenation in the direct conversion of CH to CHOH is highly dependent on the spin state of the noble metal. The results reveal that the noble metal with a higher spin magnetic moment is beneficial to the formation of the spin channels for electron transfer, which boosts the dissociation of C-H bonds. The promoted process of dehydrogenation will lead not only to the effective activation of CH but also to the easy overoxidation of CHOH. More importantly, it is found that the spin state of noble metals can be regulated by the introduction of hydroxyl (OH), which realizes the selective dehydrogenation in the process of CH direct conversion to CHOH. Among them, Ag/BN exhibits the best performance owing to the dynamic regulation spin state of a single Ag atom by OH. On the one hand, the introduction of OH significantly reduces the energy barrier of C-H bond dissociation by the increase in the spin magnetic moment. On the other hand, the high spin magnetic moment of a single Ag atom during the process of subsequent dehydrogenation can be modulated to nearly zero. As a result, the spin channel for electron transfer between the adsorbed CHOH and reactive sites is broken, which hinders its overoxidation. This work opens a new path to designing catalysts for selective dehydrogenation by tuning the spin state of local electronic structures.
甲烷（CH₄）直接转化为甲醇（CH₃OH）的关键科学挑战被认为是防止目标产物的过度氧化，这受到选择性脱氢过程难以精确控制的限制。在此，我们以具有B空位的单贵金属原子锚定六方氮化硼纳米片（M/BN）作为模型材料，首次提出CH₄直接转化为CH₃OH过程中的脱氢高度依赖于贵金属的自旋态。结果表明，具有较高自旋磁矩的贵金属有利于形成电子转移的自旋通道，从而促进C-H键的解离。脱氢过程的促进不仅会导致CH₄的有效活化，还会使CH₃OH易于过度氧化。更重要的是，发现可以通过引入羟基（OH）来调节贵金属的自旋态，从而在CH₄直接转化为CH₃OH的过程中实现选择性脱氢。其中，Ag/BN由于单个Ag原子被OH动态调节自旋态而表现出最佳性能。一方面，OH的引入通过增加自旋磁矩显著降低了C-H键解离的能垒。另一方面，在后续脱氢过程中单个Ag原子的高自旋磁矩可以被调节到接近零。结果，吸附的CH₃OH与反应位点之间的电子转移自旋通道被打破，从而阻碍了其过度氧化。这项工作为通过调节局部电子结构的自旋态来设计选择性脱氢催化剂开辟了一条新途径。
