Dandan Yuan

Effect of molten carbonate composition on the generation of carbon material

Carbon dioxide, CO2, is thought to be a main culprit leading to global climate change and a wide variety of strategies have been proposed to reduce atmospheric CO2 levels. Here, CO2 is captured and subsequently electrochemically split into carbon materials in an electrolyzer comprising a eutectic mixture of carbonates, an Fe cathode and a Ni anode, at 600 °C and current densities of 50, 100, 200 mA cm−2. SEM, EDS, XRD and BET are employed to analyze the morphology, elemental composition, crystal structure as well as the BET surface area of the synthetic cathodic products. In addition, coulomb efficiency under different electrolytic conditions is measured via the comparison between moles of formed carbon product and the Faradays of charge passed during the electrolysis reaction. This paper investigated the effect of molten carbonate compositions on carbon product generation, and confirmed the visible dependence of produced carbon on the electrolytes.

Platinum decorated hierarchical top-porous/bottom-tubular TiO2 arrays for enhanced gas phase photocatalytic activity

In this communication, Pt nanoparticles (NPs) were successfully loaded on hierarchical TiO2 nanotube arrays (TiO2 NTs) for efficient decomposition of gas phase pollutants. The loading of Pt NPs on TiO2 NTs significantly enhanced the photocatalytic activity due to reduction of the recombination of photogenerated electrons and holes.

A novel route to synthesize carbon spheres and carbon nanotubes from carbon dioxide in a molten carbonate electrolyzer

The process of molten salt CO2 capture and electrochemical conversion provides us with a new way to close the present carbon cycle and mitigate global climate change by transforming the greenhouse gas CO2 into carbonaceous fuels or chemicals. In this paper, carbon spheres and carbon nanotubes that can be used as a societal resource to serve mankind are synthesized from CO2 in diverse electrolyte composites with inexpensive metallic electrodes. Carbon products, subsequent to electrolysis, are characterized by EDS, SEM, TEM, Raman, TGA, FTIR, BET and XRD to reveal the elemental composition and morphological and structural features. The results demonstrate that Li–Ca–Na and Li–Ca–K carbonate electrolytes favor carbon sphere formation rather than carbon nanotube formation, and in particular, K2CO3 shows enhanced interference with carbon nanotube growth. In contrast, Li–Ca–Ba and Li–Ba carbonate composites present an increase in the carbon nanotube fraction. Additionally, CNTs generated from Li–K, Li–Ba and Li–Ca–Ba present a different diameter. In this way, the CO2-derived carbon products of carbon spheres and carbon nanotubes could be alternatively synthesized through the appropriate regulation of the electrolyte composition.

Syngas production: diverse H2/CO range by regulating carbonates electrolyte composition from CO2/H2O via co-electrolysis in eutectic molten salts

We present a novel sustainable method for the direct production of syngas (H2 + CO) from CO2/H2O co-electrolysis using a hermetic device, to address the continuously increasing level of environmental carbon dioxide (CO2). All experiments were conducted using a two-electrode system with a coiled Fe cathode and coiled Ni anode in eutectic mixtures of binary and ternary carbonates with hydroxide in a 0.1 : 1 hydroxide/carbonate ratio. With an applied voltage of 1.6–2.6 V and an operating temperature of 500–600 °C, the H2/CO product ratio was easily tuned from 0.53 to 8.08 through renewable cycling of CO2 and H2O. The Li0.85Na0.61K0.54CO3–0.1LiOH composite had the highest current efficiency among those tested, with an optimum value approaching ∼93%. This study provides a promising technique for the electrochemical conversion of CO2/H2O to a controllable syngas feedstock that can be used in a broad range of industrial applications.

Solar Thermo-coupled Electrochemical Oxidation of Aniline in Wastewater for the Complete Mineralization Beyond an Anodic Passivation Film

Herein, we report the solar thermal electrochemical process (STEP) aniline oxidation in wastewater for totally solving the two key obstacles of the huge energy consumption and passivation film in the electrochemical treatment. The process, fully driven by solar energy without input of any other energies, sustainably serves as an efficient thermoelectrochemical oxidation of aniline by the control of the thermochemical and electrochemical coordination. The thermocoupled electrochemical oxidation of aniline achieved a fast rate and high efficiency for the full minimization of aniline to CO2 with the stability of the electrode and without formation of polyaniline (PAN) passivation film. A clear mechanism of aniline oxidation indicated a switching of the reactive pathway by the STEP process. Due to the coupling of solar thermochemistry and electrochemistry, the electrochemical current remained stable, significantly improving the oxidation efficiency and mineralization rate by apparently decreasing the electrolytic potential when applied with high temperature. The oxidation rate of aniline and chemical oxygen demand (COD) removal rate could be lifted up to 2.03 and 2.47 times magnification compared to conventional electrolysis, respectively. We demonstrate that solar-driven STEP processes are capable of completely mineralizing aniline with high utilization of solar energy. STEP aniline oxidation can be utilized as a green, sustainable water treatment.

Carbon Dioxide Electrolysis and Carbon Deposition in Alkaline-Earth-Carbonate-Included Molten Salts Electrolyzer

The electrochemical reduction of CO2 in molten carbonates provides a comprehensive solution to end the detrimental global climate change, and convert and store conventional electricity in a stable chemical mode. In this work, we provide experimental validation of carbon deposition in CaCO3-, SrCO3- and BaCO3-dissolved electrolytes. Carbon products aggregate on the cathodic surface and are then collected and characterized by electron dispersive spectroscopy (EDS), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area analysis, and X-ray diffraction (XRD) analysis. The results demonstrate that the alkaline earth carbonate additives sustain continuous CO2 electrolysis and carbon electro-deposition. However, the micromorphology and microstructure of the carbon deposits are found to be significantly changed mainly because of the interface modification induced by the alkaline earth carbonate additives. In addition, a high yield of carbon nanotubes is observed in the cathodic carbon products by optimizing the electrolytic conditions. Compared to pure Li2CO3, alkaline earth carbonate additives provide carbon nanotubes with a thicker diameter and more prominent hollow structure.

ClO2-oxidation-based demulsification of oil-water transition layer in oilfields: An experimental study

Abstract Separation of oil and water is well known as a key process in the oil industry. For the purpose of improving the efficiency of the oil-water separation, a novel ClO2-oxidation-based demulsification method for the treatment of oil-water transition layer in oil settling tanks was proposed and studied in the present paper. A series of lab experiments were performed to investigate the techniques and conditions of the ClO2-oxidation-based demulsification, including the reaction temperature, time, concentration, etc. It was observed that a high dehydration rate of 86.11 % was achieved under an optimal reaction condition of 50oC, 4 hours, 3.5‰ ClO2 concentration and 0.5 % acid by volume. Tests concerning the corrosion to the steel tank illustrated that the corrosion rate of water layer after treated by ClO2 was lowered to 0.151 mm/a, which was below the national standard. Based on the theoretical analysis and experimental results, a mechanism was presented for understanding the ClO2 demulsification. The developed ClO2-oxidation-based demulsification technology can be practically applied to the pilot operations in oilfields.