Multiple Active Sites Engineering in Cu/γ-Al₂O₃ Catalyst Enables Selective Electrocatalytic CO₂ Reduction to Methane at High Rates

Abstract

The electrocatalytic reduction of CO₂ (CO₂RR) to methane (CH₄) using renewable electricity represents a pivotal technology for closing the anthropogenic carbon cycle. However, achieving high CH₄ Faradaic efficiency at industrially relevant current density remains challenging. This is primarily due to the complex multiple adsorption, activation, and reaction steps for CH₄ production, in which each process needs to occur efficiently at its matching catalytic active sites, so the kinetic bottlenecks exceed the capacity of single or dual-site catalysts. To address this, we engineered a Cu/Al-based multi-site heterogeneous electrocatalyst featuring atomically dispersed Cu clusters (1.5 wt.%) on a γ-Al₂O₃ matrix. Experimental and theoretical studies reveal that Cu and γ-Al₂O₃ sites predominantly serve as CO₂ (forming *CO) and H₂O molecule (yielding *H) activation centers, respectively, whereas Cu/γ-Al₂O₃ interfacial sites primarily accelerate the *CO and *H coupling to form rate-determining step intermediates (*CHO). The optimized Cu_1.5 wt.%/γ-Al₂O₃ multi-site catalyst exhibited a high CH₄ Faradaic efficiency of 72% at the current density of 500 mA cm⁻², outperforming the reported Cu-based single-site and dual-site catalysts. This study establishes combinatorial site engineering as a paradigm for overcoming scaling relations in multi-step CO₂ hydrogenation, with broad applicability in catalyst design.

Keywords

*CO interfacial hydrogenation / Cu nanoclusters / electrocatalytic CO₂ methanation / multiple sites engineering / γ-Al₂O₃ support

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