NiO/MWCNT Catalysts for Electrochemical Reduction of CO₂

This communication reports the electrochemical reduction of CO₂ on high surface area NiO/multi-walled carbon nanotube (MWCNT) catalysts. The catalysts are prepared by an incipient wetness technique with different NiO loadings. The prepared catalysts are characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) techniques. A conventional two compartments half-cell and a reverse fuel cell are employed to establish the effects of variation of NiO loading on MWCNT. The characterization results indicate that high surface area of MWCNT provides good NiO dispersion on the catalyst surface. The NiO on MWCNT also shows high electrical conductivity in the fuel cells. In CO₂ reduction, the catalysts demonstrate good CO₂ conversion activity and produce high-pressure effects even at ambient conditions. The reduction product mainly contains syngas (CO and H₂). In half-cell evaluation, an increase in current is observed with increasing NiO content up to 20 wt%. Further increase of NiO loading shows no significant increase in current density. Among the studied catalysts, NiO (20 wt%)/MWCNT displays optimum activity in both the half-cell and reverse fuel cell evaluations. With this catalyst, the total faradaic efficiency of 35.2 % is obtained at the potential of −1.7 V versus normal hydrogen electrode (NHE).