Assessing the local structure and stability of Ni and Cu based single-atom catalysts during hydrogenation reactions by operando XAS

Single-atom catalysts (SACs), consisting of isolated metal active site dispersed on suitable supports, hold great promise for maximized metal utilization, exceptional tunability of the catalytic site, and selectivity. One of their key issues is that, when the metal atom concentration exceeds a certain threshold or the catalyst is exposed to certain experimental conditions, the single atoms tend to aggregate in clusters and nanoparticles, compromising the system selectivity and activity. We propose to investigate by XAS a set of 4 Ni-SACs and 4 Cu-SACs samples, with increasing metal loadings from 0.3 to 3 wt%, supported on C3N4, in selected oxidizing/reducing environments and during the hydrogenation reaction of C2H2 to C2H4. The proposed study will provide a molecular understanding of the mechanisms leading to the aggregation of the single atoms under reaction conditions, helping to design more stable and efficient SACs.