Switching CO₂ Electroreduction Selectivity on Silver Nanoparticles from CO to Formate by Polyamidoamine Encapsulation

Silver (Ag) nanomaterials are known as attractive catalyst candidates in electrochemical CO₂ reduction reaction (CO₂RR), while achieving high selectivities beyond carbon monoxide (CO) remains a great challenge. In this work, it is demonstrated that NH₂-terminated polyamidoamine (PAMAM) dendrimer can be functionalized on Ag surface to construct an interfacial hydrogen-bond rich network, enabling to acceleration water transport and promoting water dissociation. Such a hydrogen-bond-rich interface can stabilize the key intermediates (^*HCOO, ^*OCHO^*, etc.) and trigger unique formate selectivity. As a result, the PAMAM-encapsulated Ag nanoparticles allow for switching the electrocatalytic CO₂RR selectivity from CO to formate, with a Faradaic efficiency of ≈51% (corresponding to a selectivity of 85% among carbon-based products) at -1.55 V versus reversible hydrogen electrode, significantly different from the unfunctionalized Ag nanoparticles that can only result in the CO product. The findings suggest a new perspective into the CO₂RR mechanism, and supplement a promising strategy for tuning product distributions.