Changyuan Tao

A Wearable All‐Solid Photovoltaic Textile

A solution is developed to power portable electronics in a wearable manner by fabricating an all-solid photovoltaic textile. In a similar way to plants absorbing solar energy for photosynthesis, humans can wear the as-fabricated photovoltaic textile to harness solar energy for powering small electronic devices.

Solidification/stabilization of electrolytic manganese residue using phosphate resource and low-grade MgO/CaO

In this study, P-LGMgO (low-grade MgO and NaH2PO4·2H2O), P-CaO (CaO and NaH2PO4·2H2O), and P-MgCa (low-grade MgO, CaO and NaH2PO4·2H2O) were used for the solidification/stabilization (S/S) of electrolytic manganese residue (EMR). Relevant characteristics such as ammonia nitrogen and manganese stabilization behavior, unconfined compressive strength (UCS), probable S/S mechanisms, and EMR leaching test were investigated. The results demonstrate that using P-LGMgO had higher stabilization efficiency than P-CaO and P-MgCa for the S/S of EMR at the same stabilization agent dose. The stabilization efficiency of ammonia nitrogen and manganese in the EMR were 84.0% and 99.9%, respectively, and the UCS of EMR was 5.1MPa using P-LGMgO process after curing for 28 days when the molar ratio of Mg:P was 5:1 and dose of stabilization agent was 12wt%. In this process, ammonia nitrogen was stabilized by struvite (NH4MgPO4·6H2O), and manganese by bermanite (Mn3(PO4)2(OH)2·4H2O) and pyrochroite (Mn(OH)2). The leaching test results show that the values of all the measured metals on the 28th day were within the permitted level for the GB8978-1996 test suggested by Chinas environmental protection law and the concentration of ammonia nitrogen can be reduced from 504.0mgL(-1) to 76.6mgL(-1).

Ionic liquid mediated CO2 activation for DMC synthesis

Abstract Promoted catalytic reaction between methanol and CO2 for dimethyl carbonate (DMC) synthesis is conducted over K2CO3/CH3I catalyst in the presence of ionic liquid under microwave irradiation. The effect of ionic liquids incorporated with microwave irradiation on the yield of DMC is investigated. DMC was found to form at lower temperature in a relative short time, which indicated an enhanced catalytic process by ionic liquid. Among the ionic liquids used, 1-butyl-3-methylimidazolium chloride is the most effective promoter. Density functional theory calculations indicate that CO2 bond lengths and angles changed due to the molecular interaction of ionic liquid and CO2, resulting in the activation of CO2 molecules and consequently the acceleration of reaction rate.

Hierarchical forest-like photoelectrodes with ZnO nanoleaves on a metal dendrite array

Hierarchical forest-like photoelectrodes were prepared by assembling nano-ZnO on an array of micro-metal dendrites, aiming to demonstrate the idea of highly efficient photon-harvesting inside a biomimetic dendrite structure. Via a facile aqueous electrochemical deposition process, the metal dendrites were deposited on both flat and wire substrates with different alignments, showing wide adaptability. A strong, broadband anti-reflection effect was observed, owing to the diffuse reflection inside the microdendrites. By increasing the dendrite height, the overall reflectivity of the metal electrode can be reduced from 75% to 45%, which could be further reduced to 12% after combining with acicular-leaf-like ZnO nanoarrays. Its applications in light-driven water splitting were successfully demonstrated. Taking advantage of the forest-like photoelectrode, we have artificially constructed an efficient photo-electrochemical system similar to plants in a forest, with photons harvested by the crown-like photoanodes in the sunshine, and synthetic reactions driven by the root-like electrode in the shadow.

Continuous wet-process growth of ZnO nanoarrays for wire-shaped photoanode of dye-sensitized solar cell.

Well-aligned ZnO nanorod arrays have been grown on metal-plated polymer fiber via a mild wet process in a newly-designed continuous reactor, aiming to provide wire-shaped photoanodes for wearable dye-sensitized solar cells. The growth conditions were systematically optimized with the help of computational flow-field simulation. The flow field in the reactor will not only affect the morphology of the ZnO nanorod⧹nanowire but also affect the pattern distribution of nanoarray on the electrode surface. Unlike the sectional structure from the traditional batch-type reactor, ZnO nanorods with finely-controlled length and uniform morphology could be grown from the continuous reactor. After optimization, the wire-shaped ZnO-type photoanode grown from the continuous reactor exhibited better photovoltaic performance than that from the traditional batch-type reactor.

Wet-process preparation of nickel-based photoanode for TCO-less fiber-shaped dye-sensitized solar cells

Low-cost ZnO-type fiber-shaped dye-sensitized solar cells (DSSC) without transparent conductive oxide (TCO) were for the first time assembled through a low-temperature all-wet process, using a series of Ni-based composite fiber. Both Ni layer morphology and ZnO nano-array structure evidently influenced the performance of the corresponding DSSC. For applications in both liquid type and all-solid CuI type fiber-shaped DSSCs, the Ni-based photoanode is comparable with the Ti- or Fe-based photoanode. Our all-solid CuI type fiber-shaped DSSCs was even better than that of the reported all-solid Ti- or Fe-based devices with the same oxide thickness. Electrochemical analysis further indicated that side reactions on the electrode/electrolyte interface could be effectively suppressed after a layer of Ni plated. Even for Cu wire, of which its interfacial side reactions are too complicated for application in DSSC, the Cu/Ni composite fiber still works well. Similar technology can be used to fabricate many other low-cost and light-weight conductive fibers, which are potential photoanode materials for highly efficient TCO-less DSSCs.

Periodic current oscillation catalyzed by δ-MnO2 nanosheets.

The oxygen evolution reaction (OER) is of wide interest for both fuel and hydrometallurgy applications. Different types of nanoscale MnO2 , varying from nanosheets to nanoneedles, are synthesized and assembled on the anode to investigate their catalytic effect on the nonlinear kinetics of the MnO2 -catalyzed OER at high current. For δ-MnO2 nanosheets, periodic current oscillations (PCO) occurr and occupy up to 40 % of the total energy consumption. The PCO can help to reduce the energy consumption under constant current conditions. Its amplitude could be twice of that for the previously reported MnO2 grown by an in situ electrochemical method. If the amount of γ-MnO2 nanoneedles increases, the oscillation disappears. For different Mn oxides, the rate constants of H2 O2 decomposition differ, resulting in changes in oscillation features. The results of this study may enable new ideas to improve the efficiency of industrial electrolysis and charging-discharging of supercapacitors.

Optimization of reaction conditions for the electroleaching of manganese from low-grade pyrolusite

In the present study, a response surface methodology was used to optimize the electroleaching of Mn from low-grade pyrolusite. Ferrous sulfate heptahydrate was used in this reaction as a reducing agent in sulfuric acid solutions. The effect of six process variables, including the mass ratio of ferrous sulfate heptahydrate to pyrolusite, mass ratio of sulfuric acid to pyrolusite, liquid-to-solid ratio, current density, leaching temperature, and leaching time, as well as their binary interactions, were modeled. The results revealed that the order of these factors with respect to their effects on the leaching efficiency were mass ratio of ferrous sulfate heptahydrate to pyrolusite > leaching time > mass ratio of sulfuric acid to pyrolusite > liquid-to-solid ratio > leaching temperature > current density. The optimum conditions were as follows: 1.10:1 mass ratio of ferrous sulfate heptahydrate to pyrolusite, 0.9:1 mass ratio of sulfuric acid to pyrolusite, liquid-to-solid ratio of 0.7:1, current density of 947 A/m2, leaching time of 180 min, and leaching temperature of 73°C. Under these conditions, the predicted leaching efficiency for Mn was 94.1%; the obtained experimental result was 95.7%, which confirmed the validity of the model.

Direct preparation of semiconductor iron sulfide nanocrystals from natural pyrite

Stable and monodisperse colloidal iron sulfide nanocrystal (FSNC) (<100 nm) inks were prepared directly from natural pyrite dust without any chemical conversion. After selective modification by octadecylxanthate, sedimentation behaviors of FSNCs were reversibly regulated in different mixed organic solvents. In this way, FSNCs were efficiently separated out of pyrite dust, and stable FSNC inks were then prepared. The inks were applied in drop coating semiconductor FSNC films, of which the structure and semiconductor properties were comparable with the film prepared by classical vulcanization. The FSNCs film could be further regulated simply by heating in N2 and S vapors and exhibited obvious photoconductive properties. Different from traditional synthesis processes, no chemical conversions occurred during the process from the natural pyrite to the FSNCs. Therefore, reagents and energy consumption could be largely reduced. It provides a simple yet greener way for preparing nano-sulfide semiconductors from widely existing natural sulfide ores.

A green method to leach vanadium and chromium from residue using NaOH-H 2 O 2

Hydrogen peroxide as an oxidant was applied in leaching of vanadium and chromium in concentrated NaOH solution. Under the optimal reaction conditions (the liquid to solid ratio of 4.0 ml/g, residue particle size of <200 mesh, the mass ratio of NaOH-to-residue of 1.0 g/g, the volume ratio of H2O2-to-residue of 1.2 ml/g, reaction temperature of 90 °C and reaction time of 120 min), the leaching efficiency of vanadium and chromium could reach up to 98.60% and 86.49%, respectively. Compared with the current liquid-phase oxidation technologies, the reaction temperature was 90–310 °C lower, and the NaOH concentration of the reaction medium is lower by more than 50 wt% (the mass ratio of NaOH-to-residue of 1.0 g/g equals to concentration of 20 wt%). The kinetics study revealed that leaching process of chromium and vanadium were interpreted with shrinking core model under chemical reaction control. The apparent activation energy of chromium and vanadium dissolution was 22.19 kJ/mol and 6.95 kJ/mol, respectively.