Abstract
This study highlights the importance of CO2 supply method and impact of electrolyte alkalinity in aqueous electrochemical CO2 reduction using CuxO catalyst. Two different CO2 supply methods using a two-chamber (2C) cell with CO2 purging into catholyte and a CO2 gas diffusion electrode (GDE) cell were compared. Faradaic efficiency (FE) of carbonaceous products in GDE cell was more than 3-folds higher than the 2C cell due to improved CO2 mass transfer. From the investigation of alkaline catholyte in GDE cell, the higher catholyte alkalinity led to higher current density and higher FE of carbonaceous products with a better selectivity of C2 (ethanol and ethylene). The reason lies in the OH groups around catalyst surface which improve the reaction kinetics and moreover stabilize the catalyst surface oxygen during the reduction process. With the potential of −1.17 V (RHE) in 2.0 M KOH, C2 FE of 40% and current density of −234 mA cm−2 were achieved. The production rate of ethylene and ethanol was respectively 0.105 mg min−1 and 0.035 mg min−1 on 2 cm2 electrode with CO2 flow rate 15 ml min−1, which are promising for further development and scale-up.
Highlights
The increasing demand for energy and challenges from environmental issues and climate change has led to numerous researches on sustainability and carbon recycling
Since the substance composition and morphology of CuxO catalyst changed over the electrochemical CO2 reduction reaction (eCO2RR) duration, fresh CuxO catalyst was used in each eCO2RR, with cyclic voltammetry (CV) measurements in N2 and CO2 atmosphere respectively at the beginning
The effects of CO2 supply method and alkalinity on the selectivity of carbonaceous products, and C2 products were investigated in aqueous electrolyte using CuxO catalyst
Summary
The increasing demand for energy and challenges from environmental issues and climate change has led to numerous researches on sustainability and carbon recycling. N: number of electron transfer, here it is 1 F: faradaic constant (96,485 C mol−1) j0: exchange current density (A m−2) CO(0,t)/CR(0,t): the surface concentration of oxidant/reduced product at time t. A 2C cell and a GDE cell were designed in the same dimension and fabricated by 3D printing Their eCO2RR performances were compared using the same CuxO catalyst, KHCO3 catholyte with various concentrations at a wide range of potentials. Compared to the 2C cell, GDE cell with efficient CO2 mass transfer showed more than 3-folds improvement of FE for carbonaceous products. Compared to the 2C cell, GDE cell with efficient CO2 mass transfer showed more than 3-folds improvement of FE for carbonaceous products. eCO2RR performances in GDE cell with KHCO3 and KOH with various concentrations were investigated
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