Integration of Quantum Confinement and Alloy Effect to Modulate Electronic Properties of RhW Nanocrystals for Improved Catalytic Performance toward CO₂ Hydrogenation.

Abstract

The d-band center and surface negative charge density generally determine the adsorption and activation of CO₂, thus serving as important descriptors of the catalytic activity toward CO₂ hydrogenation. Herein, we engineered the d-band center and negative charge density of Rh-based catalysts by tuning their dimensions and introducing non-noble metals to form an alloy. During the hydrogenation of CO₂ into methanol, the catalytic activity of Rh₇₅W₂₅ nanosheets was 5.9, 4.0, and 1.7 times as high as that of Rh nanoparticles, Rh nanosheets, and Rh₇₃W₂₇ nanoparticles, respectively. Mechanistic studies reveal that the remarkable activity of Rh₇₅W₂₅ nanosheets is owing to the integration of quantum confinement and alloy effect. Specifically, the quantum confinement in one dimension shifts up the d-band center of Rh₇₅W₂₅ nanosheets, strengthening the adsorption of CO₂. Moreover, the alloy effect not only promotes the activation of CO₂ to form CO₂^δ- but also enhances the adsorption of intermediates to facilitate further hydrogenation of the intermediates into methanol.