Fine Ru-Ru<sub>2</sub>P Heterostructure Enables Highly Active and Selective CO<sub>2</sub> Hydrogenation to CO
Shidong Bao, Lanqing Yang, Heyun Fu, Xiaolei Qu, Shourong Zheng
Abstract
The reverse water–gas shift (RWGS) reaction is a promising pathway for CO 2 utilization, while discovering optimal active species remains a significant challenge. Here we fabricated an ultrasmall Ru-Ru 2 P heterostructure, in which the Ru nanoparticle is in close contact with the Ru 2 P nanoparticle and modified by Ru 2 P species. Through exploring the catalytic performance of ruthenium phosphides, we found that the product selectivity for CO 2 hydrogenation can be completely tuned from CH 4 to CO through phosphidation of a SiO 2 -supported Ru catalyst because the distinctive surface structure of ruthenium phosphides interdicts the deep hydrogenation of the strongly bonded CO intermediate to CH 4 . Enhanced catalytic activity is achieved on the Ru-Ru 2 P heterostructure compared to pure Ru 2 P and RuP owing to its stronger capability to adsorb and activate CO 2 and H 2 . Following a 100 h high-temperature reaction, the Ru-Ru 2 P heterostructure remained stable with a nearly constant CO production rate and 100% CO selectivity. Furthermore, an in situ diffuse reflectance infrared Fourier transform spectroscopy study unveils that the RWGS reaction on the ruthenium phosphides proceeds through the redox mechanism. Our work demonstrates that the Ru-Ru 2 P heterostructure acts as the optimized active species with high activity and CO selectivity and highlights that the inert catalytic activity for CO intermediate hydrogenation plays a more crucial role in determining CO selectivity in catalytic CO 2 hydrogenation than the generally considered weak CO adsorption.