Alkali-decorated microenvironments aid Cu single atom catalysts in CO₂ hydrogenation

Since the advent of industrial revolution, the accumulation of carbon dioxide (CO₂) in the Earth's atmosphere has raised significant environmental and climate concerns. As a response to this pressing challenge, the conversion of CO₂ into chemicals and/or fuels through direct hydrogenation has emerged as a widely recognized and imperative strategy for mitigating both CO₂ emissions and fossil fuel consumption.

Among the array of catalysts investigated for CO₂ hydrogenation, copper (Cu)-based catalysts have garnered increasing attention for their promising potential in the production of methanol. However, despite the promising catalytic activity exhibited by Cu-based catalysts, their practical application in CO₂ hydrogenation faces a significant difficulty arising from the intrinsic reduction and aggregation tendencies of the Cu-based active centers, particularly at the elevated operating temperatures.

This propensity for reduction and aggregation could potentially result in larger Cu particles, consequently diminishing the CO₂ hydrogenation activity and leading to the generation of undesired CO byproducts. As a result, this pose a considerable impediment to simultaneously achieving the desired high catalytic activity and methanol selectivity, which are beneficial for large-scale industrial applications.

To address these challenges, the research team led by Professor Hai-Long Jiang from the University of Science and Technology of China (USTC) has proposed a novel strategy aimed at immobilizing and stabilizing single-atom Cu sites within a metal-organic framework-based catalyst by creating the Na⁺ decorated microenvironment in close proximity. The work is published in the journal National Science Review.

Through comprehensive experimental and theoretical calculation investigations, they have uncovered the importance of Na⁺-decorated microenvironment around the single-atom Cu sites. This microenvironment plays a crucial role in maintaining the atomic dispersion of Cu sites during the CO₂ hydrogenation process, even at high temperatures reaching up to 275°C, through the electrostatic interaction between Na⁺ and H^δ- species.

This exceptional stabilization effect of single-atom Cu sites has endowed the catalyst with excellent CO₂ hydrogenation activity (306 g·kg_cat^-1·h^-1), high selectivity to methanol (93%), and long-term stability, far surpassing its counterpart lacking the presence of Na⁺.

This work not only advances the development of Cu-based catalysts for selective CO₂ hydrogenation to methanol, but also introduces an effective strategy for fabricating stable single-atom sites in advanced catalysis by creating alkali-decorated microenvironments in close proximity.