Integrated electrochemical synthesis of Sn/rGO and Cu/rGO composite electrodes for CO2 electroreduction

CO₂ electrochemical reduction reaction (CO₂RR) enables CO₂ conversion into liquid and gaseous products, alleviating CO₂ concentration in the atmosphere while generating high-value compounds. Graphene-based materials have emerged as promising candidates among catalysts for CO₂RR. However, improvements in reaction kinetics and products selectivity are still needed, along with efforts to streamline catalyst synthesis, which remains energy and resource intensive. In this study, a simple, sequential electrodeposition method was developed to synthesise metal nanoparticles (Sn or Cu) directly onto reduced graphene oxide (rGO) on glassy carbon (GC) supports. Through adjustment of the deposition conditions, metal nanoparticles were deposited on the surface of GC electrodes, modified with rGO, resulting in a significant performance enhancement of the CO₂RR compared to the control tests. Not only rGO allowed an increase of electrode surface area available for nanoparticle deposition (up to 760% increase relative to the GC support area), but it also enhanced the catalytic activity through metal-support interactions. The Sn_120 s/rGO_40cyc/GC composite achieved formate production rate of 0.110 mmol h⁻¹ cm⁻², corresponding to 66% faradaic efficiency (at −1.4 V vs RHE and a current density of 8 mA cm⁻²), while the Cu_60 s/rGO_40cyc/GC electrode exhibited potential to generate a broader range of products, including carbon monoxide, formate, ethylene and methane. Although noting that further improvements are needed, this work provides a straightforward method to synthesise effective electrodes using an efficient, rapid, and cost-effective approach, demonstrating versatility in producing a wide range of CO₂RR products achieved via the controlled deposition of metal nanoparticles on in-situ rGO.