Low Potential Electrochemical CO2 Reduction to Methanol over Nickel-Based Hollow 0D Carbon Superstructure

Abstract

Electrochemical carbon dioxide reduction reaction (CO₂RR) to valuable fuels and chemical feedstock is a sustainable strategy to lower the anthropogenic CO₂ concentration, thereby dynamising the carbon cycle in the environment. CH₃OH on the other hand is undoubtedly the most desirable C₁ product of CO₂RR. However, selective electroreduction of CO₂-to-CH₃OH is very challenging and only limited catalysts are reported in literature. Pyrolyzing metal-organic frameworks (MOFs) to generate carbon matrix impregnated with metal nanoparticles, heralds exciting electrocatalytic properties. This study unveiled the morphological evolution of a mixed-ligand Ni-MOF (Ni-OBBA-Bpy) during pyrolysis, to generate Ni nanoparticles anchored 0D porous hollow carbon superstructures (Pyr-CP-800 and Pyr-CP-600). This unique morphology invokes high specific surface area and surface roughness to the materials, which synergistically facilitates the selective electroreduction of CO₂-to-CH₃OH. In comparison to most of the previously reported Ni electrocatalysts that mainly produced CO, Pyr-CP-800 selectively yielded CH₃OH with Faradaic efficiency (FE) of 32.46% at −0.60 V versus RHE (reversible hydrogen electrode) in 1.0 M KOH solution, which is highest among other reported Ni-based electrocatalysts in the literature, to best of our knowledge. Additionally, insights from density functional theory (DFT) calculations revealed that Ni (111) plane to be the active site toward the electrochemical. CO₂-to-CH₃OH formation.