From CO2 to value added chemicals: The promise of single atom catalysts

As the research community works towards the development of new catalytic materials aiming to overcome the main problem of today's catalysts (e.g., low selectivity and stability), the recently discovered single atom catalysts (SACs) appear to be promising alternatives to the widely used heterogeneous catalysts composed of nanoparticles of the active metal. SACs have rapidly attracted interest as, for certain reactions such as oxidation, WGSR and selective hydrogenation, they possess numerous advantages (high activity, stability, low cost, etc.) in comparison to their cluster and nanoparticle counterparts. Although, initially, the fabrication of these types of catalysts was considered unattainable, many researchers nowadays have successfully synthesized and tested them in a variety of catalytic reactions (oxidation, hydrogenation, etc.). Among the different reactions, the hydrogenation of CO2 is perhaps the most interesting one since the catalysts that are industrially used today suffer from low activity and stability. This work provides a comprehensive literature review of the single atom catalytic systems that have so far been employed, including both noble and transition metals, focusing exclusively on the CO2 hydrogenation reaction, in an effort to highlight the most promising features of these systems and to aid future research efforts.