Nickel ion and single-atom solution addition and electrolyzer retrofitting to enhance CO2 reduction to methane

Abstract

Electrochemical reduction of carbon dioxide to CH₄ is a key technology for achieving carbon neutrality, but its progress remains limited by insufficient product selectivity. Thus, this study systematically reveals the precise control mechanism for converting CO₂ into CH₄ by introducing Ni²⁺ and single-atom solutions as electrolyte additives. Ni²⁺ induces an electron effect by forming Cu–Ni bimetallic sites, while the single-atom solution provides an in situ proton source to promote the hydrogenation pathway, significantly enhancing conversion performance. The structure of the electrolytic cell and the electrochemical testing approach were optimized to enhance mass transfer within the reaction system. Stability experiments in flow cells reveal that at a Ni²⁺ concentration of 0.001 mol L⁻¹ in the electrolyte, the faradaic efficiency of methane reaches 48.97% at an optimized potential of −0.8 V. The maximum FE_CH4 value reaches 63.46% when using single-atom solutions as electrolyte additives. Furthermore, long-term stability experiments demonstrate that this system can sustainably produce methane for approximately 18 hours.