Unlocking the potential of zero-valent single-atom zinc for high-performance reverse water gas shift catalysis

Single Zn 0 atoms have never been employed as active sites for the reverse water gas shift (RWGS) reaction. Achieving complete CO selectivity at equilibrium CO 2 conversion using single Zn atoms for the RWGS reaction remains a significant challenge. Here, we report zinc single-atom catalysts (Zn SACs) with active species identified as Zn N 4 , Zn N 3 , Zn N 2 , and Zn 0 , synthesized from a ZIF-8 precursor via hydrogen reduction. These catalysts exhibit exceptional RWGS activity, with performance following the order: Zn-N 4  < Zn-N 3  < Zn-N 2  < Zn 0 . The Zn 0 catalyst achieves a remarkable turnover frequency (TOF) of 95.4 mol CO2 mol Zn −1  h −1 . Mechanistic studies reveal that Zn 0 sites selectively chemisorb and dissociate CO 2 into CO and active oxygen, which directly reacts with gaseous H 2 to form H 2 O via the Eley-Rideal ( E -R) mechanism, diverging from the traditional Langmuir-Hinshelwood (L-H) pathway. These findings provide insights into the new active species and reaction mechanisms of Zn SACs, advancing sustainable catalytic systems for CO 2 conversion.