Rational design of precious tetrametallic single-cluster catalysts for electrocatalytic nitrate reduction reaction

Abstract

Single cluster catalysts (SCCs) with high metal loading can exhibit extraordinary catalytic activity in electrocatalytic reactions, but the rational design of active sites remains a challenge. Herein, we proposed a series of SCCs with pyramid-shaped precious tetrametallic clusters anchored on g-CN monolayer (M4/g-CN) as efficient catalysts for the electrochemical reduction of nitrate to ammonia (NO3RR). By means of first-principle computations, the stability, catalytic mechanism and activity, as well as selectivity of these SCCs are systematically investigated. The calculation results show that most SCCs (Ru4/g-CN, Rh4/g-CN, Pd4/g-CN, Os4/g-CN, Ir4/g-CN, Pt4/g-CN) are thermodynamically stable due to the strong binding energy and significant charge transfer behavior between tetrametallic clusters and g-CN support. More important, the volcano curve between limiting potentials and adsorption free energy of NO3‾ can be established, in which Ir4/g-CN can exhibit optimal NO3RR activity due to its location of volcano top. Further analysis of electronic structures reveals that the special pyramid configuration can significantly promote the enrichment of charge on active site and elevate its d-band center, and thus facilitates the NO3RR. This finding pours new vigor into the development of the SCCs family.