中国科学技术大学熊宇杰团队揭示了Pd修饰的ZnO-Au杂化材料高效光催化甲烷转化为乙烯的中间体形成和脱氢过程。相关研究成果于2020年12月29日发表在国际顶尖学术期刊《美国化学会志》。

光催化为在温和条件下将甲烷转化为多碳化合物(C2+)提供了一种有趣的方法；然而，由于甲基自由基是唯一的反应中间体，目前的C2+产品主要是乙烷，对乙烯的选择性可以忽略不计，而乙烯是一种关键的化工原料，具有比乙烷更高的附加值。

该文中，研究人员开发了一种直接的光催化甲烷转化为乙烯的途径，涉及在Pd修饰的ZnO–Au杂化催化剂上烷氧基（即甲氧基和乙氧基）中间体的形成和脱氢。在各种原位表征的基础上，揭示了催化剂的Pd诱导脱氢能力是开启该途径的关键。在反应过程中，甲烷分子在钯的辅助下首先在氧化锌表面分解成甲氧基。这些中间产物可与乙烯进一步偶联成甲氧基，然后再与乙氧基脱氢。

结果表明，经过优化的ZnO-AuPd杂化材料在光照8h后，甲烷转化率为536.0μmol g^-1，C2+化合物选择性为96.0%（C2H4和C2H6的总生成量分别为39.7%和54.9%）。

该工作为温和条件下甲烷转化途径提供了新的见解，并强调了脱氢对于增强光催化活性和不饱和烃产物选择性的重要性。

附：英文原文

Title: Pd-Modified ZnO–Au Enabling Alkoxy Intermediates Formation and Dehydrogenation for Photocatalytic Conversion of Methane to Ethylene

Author: Wenbin Jiang, Jingxiang Low, Keke Mao, Delong Duan, Shuangming Chen, Wei Liu, Chih-Wen Pao, Jun Ma, Shuaikang Sang, Chang Shu, Xiaoyi Zhan, Zeming Qi, Hui Zhang, Zhi Liu, Xiaojun Wu, Ran Long, Li Song, Yujie Xiong

Issue&Volume: December 29, 2020

Abstract: Photocatalysis provides an intriguing approach for the conversion of methane to multicarbon (C2+) compounds under mild conditions; however, with methyl radicals as the sole reaction intermediate, the current C2+ products are dominated by ethane, with a negligible selectivity toward ethylene, which, as a key chemical feedstock, possesses higher added value than ethane. Herein, we report a direct photocatalytic methane-to-ethylene conversion pathway involving the formation and dehydrogenation of alkoxy (i.e., methoxy and ethoxy) intermediates over a Pd-modified ZnO–Au hybrid catalyst. On the basis of various in situ characterizations, it is revealed that the Pd-induced dehydrogenation capability of the catalyst holds the key to turning on the pathway. During the reaction, methane molecules are first dissociated into methoxy on the surface of ZnO under the assistance of Pd. Then these methoxy intermediates are further dehydrogenated and coupled with methyl radical into ethoxy, which can be subsequently converted into ethylene through dehydrogenation. As a result, the optimized ZnO–AuPd hybrid with atomically dispersed Pd sites in the Au lattice achieves a methane conversion of 536.0 μmol g–1 with a C2+ compound selectivity of 96.0% (39.7% C2H4 and 54.9% C2H6 in total produced C2+ compounds) after 8 h of light irradiation. This work provides fresh insight into the methane conversion pathway under mild conditions and highlights the significance of dehydrogenation for enhanced photocatalytic activity and unsaturated hydrocarbon product selectivity.

DOI: 10.1021/jacs.0c10369

Source: https://pubs.acs.org/doi/10.1021/jacs.0c10369