A microfluidic all-vanadium photoelectrochemical cell with a full-spectrum-responsive Ti2O3 photoanode for efficient solar energy storage

The all-vanadium photoelectrochemical cell is one of the promising solar energy storage technologies. However, conventional photoanodes surfer from low solar energy utilization efficiency as a result of narrow spectrum response and poor mass transfer.Hence, in this study, a microfluidic all-vanadium photoelectrochemical cell with a full-spectrum-responsive Ti2O3 photoanode was proposed for efficient solar energy storage. Experimental results indicated that the Ti2O3 photoanode responded to almost the full spectrum of sunlight and exhibited excellent photoresponse and operation stability, which facilitated efficient solar energy utilization. Additionally, the effects of the light intensity, vanadium ion concentration, and electrolyte flow rate were studied. It was found that increasing the light intensity and vanadium ion concentration and reducing the electrolyte flow rate promoted photoelectrochemical reactions and thus improved the solar energy storage performance. The obtained results demonstrate the feasibility and superiority of using Ti2O3 as the photoanode for a photoelectrochemical cell to achieve efficient solar energy storage.

Recent advances in photoelectrochemical sensors for detection of ions in water

Over the last 50 years,the explosive adoption of modern agricultural practices has led to an enormous increase in the emission of non-biodegradable and highly biotoxic ions into the hydrosphere.Excess intake of such ions,even essential trace elements such as Cu^(2+)and F^(-),can have serious consequences on human health.Therefore,to ensure safe drinking water and regulate wastewater discharge,photoelectrochemical(PEC)online sensors were developed,with advantages such as low energy consumption,inherent miniaturization,simple instrumentation,and fast response.However,there is no publicly available systematic review of the recent advances in PEC ion sensors available in the literature since January 2017.Thus,this review covers the various strategies that have been used to enhance the sensitivity,selectivity,and limit of detection for PEC ion sensors.The photoelectrochemically active materials,conductive substrates,electronic transfer,and performance of various PEC sensors are discussed in detail and divided into sections based on the measurement principle and detected ion species.We conclude this review by highlighting the challenges and potential future avenues of research associated with the development of novel high-performance PEC sensors.

Investigation on lateral dispersion characteristics of fuel particles in dense phase zone of a large-scale circulating fluidized bed boiler under combustion conditions

The dispersion characteristics of fuel particles in the dense phase zone in circulating fluidized bed(CFB)boilers have an important influence on bed temperature distribution and pollutant emissions.However,previous research in literature was mostly on small-scale apparatus,whose results could not be applied directly to large-scale CFB with multiple dispersion sources.To help solve this problem,we proposed a novel method to estimate the lateral dispersion coefficient(Dx)of fuel particles under partial coal cut-off condition in a 35o MW supercritical CFB boiler based on combustion and dispersion models.Meanwhile,we carried out experiments to obtain the Dx in the range of 0.1218-0.1406 m2/s.Numerical simulations were performed and the influence of operating conditions and furnace structure on fuel dispersion characteristics was investigated,the simulation value of Dx was validated against experimental data.Results revealed that the distribution of bed temperature caused by the fuel dispersion was mainly formed by char combustion.Because of the presence of intermediate water-cooled partition wall,the mixing and dispersion of fuel and bed material particles between the left and right sides of the furnace were hindered,increasing the non-uniformity of the bed temperature near furnace front wall.

Characterization of the start-up behavior and steady-state performance of biotrickling filter removing low concentration toluene waste gas

A biotrickling filter packed with the regular ceramic spheres was designed and fabricated to purify the low toluene-concentration waste gas.Particular attention was made to the study of the start-up behavior of the biotrickling filter.Moreover,the steady performances were investigated to establish the experimental correlation between the operation factors and removal efficiency.It was found that the start-up process of the biotrickling filter exhibited three stages including the biofilm formation,biofilm development,and biofilm stabilization.The OD600 nm of the circulated liquid,gas pressure drop,elimination capacity,and temperature rise maintained at a rather low level in the biofilm formation stage,then increased rapidly in the biofilm development stage,and finally reached a stable value in the biofilm stabilization stage.It was also found that the removal efficiency of the biotrickling filter in the stable period decreased with increase in the waste gas flow rate,circulated liquid flow rate,and diameter of the ceramic sphere.More interestingly,it was revealed the operation modes have a significant influence on the removal efficiency of the biotrickling filter,and the microorganism show a high activity under the operating temperature ranging from 30°C to 40°C.The experimental correlations for describing the effect of operation factors on the removal efficiency of the biotrickling filters under both the co-current and counter-current operation modes were obtained.The correlation results are in good agreement with the experimental data.

Numerical investigation of the moving liquid column coalescing with a droplet in triangular microchannels using CLSVOF method

The dynamic behavior of the moving liquid column coalescing with a sessile droplet in triangular microchannels is numerically investigated by using coupled volume of fluid with level set interface tracking method implemented in ANSYS Fluent 14.5 in conjunction with the continuum surface force model. It is found that for both hydrophobic and hydrophilic microchannels, the coalescence between the moving liquid column and droplet can accelerate the original liquid column movement as a result of the induced curvature that lowers the liquid pressure at the interface. As compared to the rectangular microchannel with the same hydraulic diameter, the triangular microchannel exhibits smaller velocity increment ratio because of stronger viscous effect. Simulation results also reveal that the velocity increment ratio increases with the contact angle in hydrophobic microchannels, but it is reverse in the hydrophilic microchannels. The effects of the droplet size, lengthways and transverse positions are also investigated in this work. It is shown that larger droplet and smaller distance between the droplet and inlet or the substrate center can result in larger velocity increment ratio as a result of higher surface energy and lower viscous dissipation energy, respectively. The results obtained in this study create a solid theoretical foundation for designingand optimizing microfluidic devices encountering such a typical phenomenon.

Statistical and frequency analysis of the pressure fluctuation in a fluidized bed of non-spherical particles

In this paper, the pressure fluctuation in a fluidized bed was measured and processed via standard devia- tion and power spectrum analysis to investigate the dynamic behavior of the transition from the bubbling to turbulent regime. Two types （Geldart B and D） of non-spherical particles, screened from real bed materials, and their mixture were used as the bed materials. The experiments were conducted in a semi- industrial testing apparatus. The experimental results indicated that the fluidization characteristics of the non-spherical Geldart D particles differed from that of the spherical particles at gas velocities beyond the transition velocity Uo The standard deviation of the pressure fluctuation measured in the bed increased with the gas velocity, while that measured in the plenum remained constant. Compared to the coarse particles, the fine particles exerted a stronger influence on the dynamic behavior of the fluidized bed and promoted the fluidization regime transition from bubbling toward turbulent. The power spectrum of the pressure fluctuation was calculated using the auto-regressive （AR） model; the hydrodynamics of the flu- idized bed were characterized by the major frequency of the power spectrum of the pressure fluctuation. By combining the standard deviation analysis, a new method was proposed to determine the transition velocity Uk via the analysis of the change in the major frequency. The first major frequency was observed to vary within the range of 1.5 to 3 Hz.

Medium-low temperature hydrothermal hydrolysis kinetic characteristics of concentrated wet microalgae biomass

To improve microalgae biomass utilization efficiency during biofuel production process,medium-low temperature hydrothermal hydrolysis pretreatment was adopted in this study.The pretreatment kinetic characteristics of concentrated wet microalgae Chlorella vulgaris biomass(50 g/L)under medium-low temperature hydrolysis(100°C-200°C)were experimentally investigated.The hydrothermal hydrolysis kinetics describing the coupled effects of temperature,initial pressure and retention time then were proposed using response surface methodology(RSM).The maximum carbohydrate yield reached 327.3 mg/g dried biomass under initial pressure of 4 MPa at reaction temperature of 150°C for 120 min.The maximum protein yield(321.5 mg/g dried biomass)was obtained under initial pressure of 4 MPa at reaction temperature of 200°C for 60 min.Based on the hydrothermal hydrolysis kinetic models,it was confirmed that temperature was the most important factor affecting both carbohydrate and protein release during hydrothermal hydrolysis process.Hydrothermal initial pressure and retention time were significant to carbohydrate release,but not to protein release.While,lipid was mainly distributed in microalgae residual and almost did not exist in supernatant(about 8.03 mg/g).And with assistance of mixed hexane and methanol(the ratio of hexane to methanol was 7:3),67.69%of microalgae lipid was extracted out from hydrothermal hydrolysed microalgae residual(123.3 mg/g dried biomass).

Simulation of mesoscale interfacial properties using the lattice Boltzmann method

We derive the mesoscopic interparticle potentials from macroscopic thermodynamics for van der Waals,Redlich-Kwong,and Redlich-Kwong-Soave equations of state and find that all these potentials are very similar to the Lennard-Jones potential.To investigate the interfacial property at the mesoscale level,we incorporate free energy functions into the single-component multiphase lattice Boltzmann model and obtain the saturated density coexistence curves and interface mass density profiles across the interface using this method with different equations of state.The simulation results accurately reproduce the properties of equilib-rium thermodynamics.Numerical results for single-component phase transitions indicate that a bubble-growth process is obtained and the equilibrium phase diagram is achieved at a given temperature.Bulk free energy,the interfacial energy coefficient,and other properties of nonequilibrium thermodynamic parameters,which are used to examine interfacial properties,are obtained in these simulations,and all these parameters are found to obey irreversible thermodynamics.

High temperature co-firing of 3D-printed AleZnO/Al_(2)O_(3) multimaterial two-phase flow sensor

Sensors are crucial in the understanding of machines working under high temperatures and highpressure conditions.Current devices utilize polymeric materials as electrical insulators which pose a challenge in the device's lifespan.Ceramics,on the other hand,is robust and able to withstand high temperature and pressure.For such applications,a co-fired ceramic device which can provide both electrical conductivity and insulation is beneficial and acts as a superior candidate for sensor devices.In this paper,we propose a novel fabrication technique of complex multi-ceramics structures via 3D printing.This fabrication methodology increases both the geometrical complexity and the device's shape precision.Structural ceramics(alumina)was employed as the electrical insulator whilst providing mechanical rigidity while a functional ceramic(alumina-doped zinc oxide)was employed as the electrically conductive material.The addition of sintering additives,tailoring the printing pastes'solid loadings and heat treatment profile resolves multi-materials printing challenges such as shrinkage disparity and densification matching.Through high-temperature co-firing of ceramics(HTCC)technology,dense high quality functional multi-ceramics structures are achieved.The proposed fabrication methodology paves the way for multi-ceramics sensors to be utilized in high temperature and pressure systems in the near future.

Water flooding behavior in flow cells for ammonia production via electrocatalytic nitrogen reduction

The green production of ammonia,in an electrochemical flow cell under ambient conditions,is a promising way to replace the energy-intensive Haber-Bosch process.In the operation of this flow cell with an alkaline electrolyte,water is produced at the anode but also required as an essential reactant at the cathode for nitrogen reduction.Hence,water from the anode is expected to diffuse through the membrane to the cathode to compensate for the water needed for nitrogen reduction.Excessive water permeation,however,tends to increase the possibility of water flooding,which would not only create a large barrier for nitrogen delivery and availability,but also lead to severe hydrogen evolution as side reaction,and thus significantly lower the ammonia production rate and Faradaic efficiency.In this work,the water flooding phenomenon in flow cells for ammonia production via electrocatalytic nitrogen reduction is verified via the visualization approach and the electrochemical cell performance.In addition,the effects of the nitrogen flow rate,applied current density,and membrane thickness on the water crossover flux and ammonia production rate are comprehensively studied.The underlying mechanism of water transport through the membrane,including diffusion and electro-osmotic drag,is precisely examined and specified to provide more insight on water flooding behavior in the flow cell.