(658f) Boosting Ethanol Selectivity in Electrocatalytic CO2 Reduction Reaction through Confinement of Intermediates in Au/Cu Tandem Catalyst

In electro-catalytic reduction of CO₂, achieving high conversion efficiency of multi-carbon (C₂₊) products is crucial. Cu is known to be only metal capable of reducing CO₂ to C₂₊ products. Various studies have shown that increasing local concentration of intermediates such as OH^- and CO*, induced by confined structure like nanowires and nanocavities, is effective in improving the selectivity of C₂₊ products. Recently, combining CO-selective metal such as Au and Ag with Cu catalysts also reported to increase local concentration of CO. This tandem catalyst operates by a sequential reaction where CO produced on the CO-selective metal surface acts as a reactant on the Cu surface.

In this study, we aimed to investigate effect of each confined structure and tandem, and to maximize the local confinement effect by combining both confined and tandem structures. We designed a nanostructure consisting of two parts: a metal film layer on the bottom and a porous Cu layer on top. To investigate confined structure effect, Cu was used for metal film layer (Cu_bottom/Cu_pore) with different pore size. On Cu_bottom/Cu_pore catalyst, selectivity of EtOH was highly influenced by pore size, and highest on 50 nm of pore diameter. To investigate tandem effect, Au was used for metal film layer (Au_bottom/Cu_pore), and combination of confined and tandem effects resulted in increased selectivity of C₂₊ products compare to Cu_bottom/Cu_pore, regardless of pore size. Especially, the selectivity of EtOH reached 50.8 % at -0.9 V vs RHE. The locally confined intermediates and reaction pathway in tandem porous catalyst was inferred through in-situ ATR-SEIRAS.

In summary, the novel nanostructure allowed us to identify the optimal confined structure dimensions for EtOH selectivity, resulting in significant improvement in EtOH selectivity on the tandem confined structure.