Asymmetric Charge Distribution in Atomically Precise Metal Nanoclusters for Boosted CO Reduction Catalysis.

Recently, atomically precise metal nanoclusters (NCs) have been widely applied in CO reduction reaction (CORR), achieving exciting activity and selectivity and revealing structure-performance correlation. However, at present, the efficiency of CORR is still unsatisfactory and cannot meet the requirements of practical applications. One of the main reasons is the difficulty in CO activation due to the chemical inertness of CO. Constructing symmetry-breaking active sites is regarded as an effective strategy to promote CO activation by modulating electronic and geometric structure of CO molecule. In addition, in the subsequent CORR process, asymmetric charge distributed sites can break the charge balance in adjacent adsorbed C intermediates and suppress electrostatic repulsion between dipoles, benefiting for C-C coupling to generate C products. Although compared to single atoms, metal nanoparticles, and inorganic materials the research on the construction of asymmetric catalytic sites in metal NCs is in a newly-developing stage, the precision, adjustability and diversity of metal NCs structure provide many possibilities to build asymmetric sites. This review summarizes several strategies of construction asymmetric charge distribution in metal NCs for boosting CORR, concludes the mechanism investigation paradigm of NCs-based catalysts, and proposes the challenges and opportunities of NCs catalysis.