Chengyu Ma

Aqueous CO2 reduction on morphology controlled CuxO nanocatalysts at low overpotential

Various CuxO catalysts with different special microstructures were synthesized using a simple one-step hydrothermal method by controlling the reaction time and temperature conditions. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) were used to observe the morphologies of the received catalysts. The 3-dimensional (3D) hierarchical nanospheres (500 nm) comprised of secondary structured nanorods (50 nm) are formed at 180 °C for 2 hours. However, when increasing the hydrothermal reaction temperature to 220 °C, solid microspheres with a large size of 2.5 μm begin to appear instead of flabby hierarchical nanospheres. To further investigate the effect of morphologies on the activity and production selectivity of CuxO catalysts, cyclic voltammetry (CV) was used to evaluate the onset potential and current density of catalyzed CO2 reduction combining linear sweep voltammetry (LSV) in 0.5 M KHCO3 solution. The effect of catalyst loading was also tested by applying the gas diffusion layer (GDL) to make up a working electrode for CO2 electroreduction. The results indicate that the synthesized temperature of 180 °C for 2 h is the optimal condition for CuxO nanospheres and the optimal loading is about 3 mg cm−2, under which the onset potential for CO2 electroreduction reaches −0.55 V vs. SHE. By ion chromatography measurement, the faradaic efficiency and production rate of produced formate was found to be 59%, which is much higher than most reported Cu-based catalysts at the same electrolysis conditions, indicating the high selectivity of the CuxO nanospheres due to their controlled special surface morphology.

Study on simultaneous adsorption of Zn(II) and methylene blue on waste-derived activated carbon for efficient applications in wastewater treatment

Abstract Organic and inorganic pollutants often coexist in water bodies due to the influxes of pollutants from various pollution sources. The use of waste-derived adsorbents to remove pollutants is an economical and efficient method of wastewater treatment. The present study was designed to investigate the adsorption and cosorption of Zn and methylene blue (MB) on a capsicum straw derived activated carbon (CSAC), by determining equilibrium adsorption isotherms and simulation. The result showed that Langmuir equation is more suitable for description of the adsorption isotherms of Zn2+ and MB than that of Freundlich equation. The maximum adsorption amounts for both adsorbates were quite the same. The amount of Zn2+ adsorbed decreases with increasing MB and vice versa, suggesting the competitive rather than synergistic adsorption on the activated carbon. Cosorption of Zn(II) and MB on the CSAC showed MB to be preferentially adsorbed. The adsorption kinetic studies showed that the adsorption of Zn2+ comply with pseudo-second-order rate model rather than pseudo-first-order rate model. The findings of the present study helps to carry out an efficient application in waste treatment.