Programming CO and syngas production under large current density via lanthanide family-guided doped silver aerogels in electrochemical CO2 reduction

Controlling product selectivity and tunability in the electrochemical reduction of CO 2 (eCO 2 RR) is crucial for enabling large-scale production of CO and syngas as carbon-neutral feedstocks. Here, we introduce a lanthanide (Ln)-directed strategy. We demonstrate that different Ln-oxide dopants exhibit distinct 4f-derived electronic effects, with CO selectivity increasing from Ce to Eu and then declining toward Tm. This Ln-oxide dopant-dependent modulation enables superior performance at industrially relevant current densities, where Ag 95 Eu 5 delivers benchmark CO production (CO selectivity = 96%, carbon utilization ≈70%, current density = 500 mA/cm 2 ) with excellent stability, while Ag 95 Ce 5 generates tunable syngas with an H 2 /CO ratio of 2.1 at both 100 mA/cm 2 and 1.5 at 500 mA/cm 2 . Density functional theory (DFT) reveals that Eu-oxide doping donates interfacial electron density to the bulk Ag 100 slabs through its occupied 4f orbital, slightly elevating the local Fermi level electronic density and stabilizing *COOH and *CO intermediates, lowering the eCO 2 RR energy barriers and favouring CO formation. In contrast, Ce-oxide doping produces an electron-deficient interface with unoccupied 4f states positioned above the Fermi level that weakens the *CO binding and subsequently facilitates syngas production. Our study establishes the use of Ln-oxides for modulating the electronic structure of a catalyst, resulting in a highly versatile and tunable catalytic system.