Selective Photo-oxidation of Methane to Methanol with Oxygen over Dual-Cocatalyst-Modified Titanium Dioxide,ACS Catalysis

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Selective Photo-oxidation of Methane to Methanol with Oxygen over Dual-Cocatalyst-Modified Titanium Dioxide
ACS Catalysis ( IF 11.3 ) Pub Date : 2020-11-23 , DOI: 10.1021/acscatal.0c04329
Hui Song _{1,

2} , Xianguang Meng _{1,

3} , Shengyao Wang _{1,

4} , Wei Zhou ₅ , Shuang Song ₁ , Tetsuya Kako ₁ , Jinhua Ye _{1,

2,

6}

Affiliation

Direct and selective oxidation of CH₄ with dioxygen to methanol is a “dream reaction” in modern catalysis yet remains a great challenge. Here, we report that TiO₂ loaded with dual cocatalysts, that is, nanometals and cobalt oxide (CoO_x) nanoclusters, is capable of selectively catalyzing CH₄ to CH₃OH at room temperature under photoexcitation using abundant and inexpensive O₂ as an oxidant. The best activity for the formation of the primary products, CH₃OOH and CH₃OH, is up to 50.8 μmol for 2 h with 95% selectivity. Mechanistic studies elucidate that the superior activity and selectivity result from the synergistic effect of nanometals and CoO_x. Nanometals enhance CH₄ conversion by promoting the separation of the photoexcited electron and the reduction of O₂. The CoO_x mediates a mild CH₄ oxidation process by suppressing the formation of highly oxidative ^•OH radicals that can further oxidize CH₃OH to HCHO and CO₂, thereby preserving a high selectivity toward oxygenated products. This work provides a prototype in designing efficient photocatalysts for selective oxidation of CH₄ to CH₃OH with O₂ under mild conditions.

中文翻译：

在双助催化剂修饰的二氧化钛上用氧气将甲烷选择性光氧化为甲醇

在现代催化中，用双氧将CH ₄直接选择性氧化为甲醇是一个“梦想反应”，但仍然是一个巨大的挑战。在此，我们报道了负载有双重助催化剂（即纳米金属和氧化钴（CoO _x）纳米团簇）的TiO ₂能够在室温下在光激发下使用大量廉价的O ₂作为氧化剂选择性催化CH ₄至CH ₃ OH。。形成初级产物CH ₃ OOH和CH ₃的最佳活性OH在2小时内达到50.8μmol，选择性为95％。机理研究表明，优异的活性和选择性是由纳米金属和CoO _x的协同作用产生的。纳米金属通过促进光激发电子的分离和O ₂的还原来增强CH _4的转化。CoO _x通过抑制可进一步将CH ₃ OH氧化为HCHO和CO ₂的高度氧化^• OH自由基的形成，介导了温和的CH ₄氧化过程，从而保持了对氧化产物的高选择性。这项工作为设计用于CH ₄选择性氧化的有效光催化剂提供了一个原型。在温和条件下用O ₂转化为CH ₃ OH 。

更新日期：2020-12-04

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