Seeding Atomic Silver into Internal Lattice Sites of Transition Metal Oxide for Advanced Electrocatalysis

Transition metal oxides (TMOs) are widely studied for loading of various catalysts due to their low cost and high structure flexibility. However, the prevailing close-packed nature of most TMOs crystals has restricted the available loading sites to surface only, while their internal bulk lattice remains unactuated due to the inaccessible narrow space that blocks out most key reactants and/or particulate catalysts. Herein, using tunnel-structured MnO₂, this study demonstrates how TMO's internal lattice space can be activated as extra loading sites for atomic Ag in addition to the conventional surface-only loading, via which a dual-form Ag catalyst within MnO₂ skeleton is established. In this design, not only faceted Ag nanoparticles are confined onto MnO₂ surface by coherent lattice-sharing, Ag atomic strings are also seeded deep into the sub-nanoscale MnO₂ tunnel lattice, enriching the catalytically active sites. Tested for electrochemical CO₂ reduction reaction (eCO₂RR), such dual-form catalyst exhibits a high Faradaic efficiency (94%), yield (67.3 mol g^-1 h^-1) and durability (≈48 h) for CO production, exceeding commercial Ag nanoparticles and most Ag-based electrocatalysts. Theoretical calculations further reveal the concurrent effect of such dual-form catalyst featuring facet-dependent eCO₂RR for Ag nanoparticles and lattice-confined eCO₂RR for Ag atomic strings, inspiring the future design of catalyst-substrate configuration.