Hierarchically Porous CuAg via 3D Printing/Dealloying for Tunable CO₂ Reduction to Syngas

Electrochemical CO₂ reduction reaction (CO₂RR) coupled with hydrogen evolution reaction (HER) is a renewable route to produce syngas (CO + H₂), an essential feedstock for liquid fuel production. However, the development of high-performance electrocatalyst with tunable H₂/CO ratio, high-rate syngas production, and long-term electrochemical stability remains challenging. Here, a metal three-dimensional (3D) printing technique followed by dealloying was utilized to develop three-dimensional hierarchical porous (termed as 3D hp) CuAg catalysts for the concurrent generation of CO and H₂. By purposely designing the precursor compositions, the resultant 3D hp CuAg catalysts with a high density of phase-segregated Ag and Cu nanodomains exhibit a tunable H₂/CO ratio from 3:1 to 1:2. Through further porosity engineering, the 3D hp CuAg catalysts show significantly enhanced syngas production rate of 140 μmol/h/cm² and electrochemical stability up to 140 h (which is the highest value reported so far). The remarkable electrochemical stability of the 3D hp CuAg arises from three-level hierarchical porous configurations, wherein the macroporous structure benefits gas bubble growth and detachment, the microporous structure stabilizes the active nanoporous layer, while the nanoporous structure provides a large active surface area and enables efficient mass transfer. The results of this study offer a new vision for the development of hierarchically porous catalysts for CO₂ reduction.