Efficient electrochemical conversion of CO2 into formic acid using colloidal NiCo@rGO catalyst

A simple approach was used to synthesize a catalyst based on colloidal NiCo with rGO support. The catalyst was uniformly deposited on acid-treated Sn foil using drop-casting method. The prepared NiCo@rGO catalyst was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The XRD measurements confirmed the development of a homogenously immersed structure with a specific NiCo composition. The different ratios of Ni and Co in the NiCo@rGO catalyst were further confirmed by XPS and SEM-EDX. The catalyst was tested for the electrochemical reduction of CO2 to produce formic acid (HCOOH) and resulted in a significantly higher faradaic efficiency at −50 mA current compared to the simple Co nanoparticle, rGO, Sn foil, Ni nanoparticles, and NiCo composite. The colloidal NiCo bimetallic structure, combined with the rGO support on the treated Sn foil, played an important role in enhancing the catalytic activity and selectivity towards formic acid. When comparing the NiCo@rGO catalyst with other catalysts, especially Ni, Co, Sn foil, NiCo, and rGO, the NiCo@rGO catalyst showed superior CO2 electrochemical chemical reduction performance. The results suggest that the synergic effect of combining Ni with Co along with using acid-treated Sn foil as a support is responsible for the high activity towards formic acid production. The experimental results demonstrated the formation of formic acid with low energy consumption and good faradic efficiency.