Metal-Oxide Nanotube Channel Microenvironment Inducing Strong Metal-Oxide Interplay: A Case Study with CO<sub>2</sub> Hydrogenation to Methanol
Ying Zhang, Guijun Liu, Linghui Bian, Wenjing Sun, Xiaomin Hu, Gao Yanhao, Fengying Gao, Xin Zhang, Biaohua Chen, Ning Wang
Abstract
Nanoconfined architectures and interfacial electronic modulation are essential strategies for enhancing catalytic performance in multistep reactions. While carbon nanotubes (CNTs) are commonly used for confinement, their chemical inertness limits the formation of synergistic active sites and optimization of the reaction environment. Replacing CNTs with metal-oxide nanotubes offers significant improvements in electronic metal–support interaction (EMSI), tunable structure, mass transfer, and stability. Nevertheless, research on confinement effects in metal-oxide nanotubes remains underexplored. Herein, using the CO 2 hydrogenation as the model reaction, we engineered two distinct palladium–titania nanotube configurations: Pd@TiO 2 NTs (with Pd confined within nanotubes) and Pd/TiO 2 NTs (with Pd deposited on external surfaces). Density functional theory (DFT) calculations reveal that Pd@TiO 2 NTs exhibit enhanced EMSI, suppress the reverse water gas shift (RWGS) reaction, and promote methanol production more than Pd/TiO 2 NTs. Consistently, experimental results show that Pd@TiO 2 NTs achieve a 3.7-fold higher methanol selectivity and 2.4-fold higher CO 2 conversion compared with Pd/TiO 2 NTs. Moreover, Pd@TiO 2 NTs also demonstrates a space–time yield of 0.56 mmol g cat –1 h –1, approximately 9 times higher than that of Pd/TiO 2 NTs. This significant finding provides critical guidance for engineering spatially confined catalysts utilizing metal-oxide nanotubes in heterogeneous catalytic systems.