High Geometric Area Research Articles

Electrocatalytic reduction of CO2 with N/B co-doped reduced graphene oxide based catalysts

Metal based materials are frequently used in electrocatalytic processes for the mitigation of CO2emissions, increasing the cost of the technology and the toxicity of the material. Metal-free catalysts appear as an interesting alternative. This work focusses on the synthesis of nitrogen and boron doped reduced graphene oxide (rGO) for the electrocatalytic reduction of CO2in gas phase in continuous operation mode in a PEM type cell. The main reaction products observed have been formic acid and CO, being the first one mainly formed.Results obtained with rGONB have been compared with the undoped rGO and withcopper-based catalysts (Cu/rGO and Cu/rGONB).The non-metal doped material (rGONB) is much more active in the CO2electrocatalytic reduction as compared with the undoped material (rGO).The catalytic activity of rGONB is very similar to those obtained with Cu/rGO and Cu/rGONB catalysts, pointing out rGONB as a very promising material for the electrocatalytic reduction of CO2. This is especially relevant considering that rGONB has been tested in a relatively high geometric area (compared with most works in literature), in gas phase and in continuous operation mode, which is an important step to carry out the further scale-up of the process for industrial applications.

Scalable Fabrication of Cu2S@NiS@Ni/NiMo Hybrid Cathode for High‐Performance Seawater Electrolysis

AbstractElectrochemical hydrogen evolution reaction (HER) with cost‐effectiveness, high performance, and repeatable scale‐up production hold promises for large‐scale green hydrogen generation technology. Herein, a convenient method for scaling up Cu2S@NiS@Ni/NiMo electrocatalysts on Cu foam with high geometric area over 100 cm2 is presented. The hybrid electrode exhibits high hydrogen evolution activity with 190 and 250 mV overpotential at 1000 mA cm−2 and superior stability with negligible overpotential loss after over 2000 h at 500 mA cm−2 under steady‐state conditions in both artificial seawater and real seawater. Detailed characterizations and simulations demonstrate that high intrinsic activity resulting from the unique boundary interface, enhance mass transport resulting from superaerophobic nanoarray architecture, and corrosion resistance resulting from polyanion‐rich passivating layers together lead to the outstanding performance. The practicability is also demonstrated in an alkaline seawater electrolyzer coupling with the hybrid electrode and stable commercial anode.

Optical and electrochemical detection of a verotoxigenic E. coli gene using DNAzyme-labeled stem-loops

The activity of a peroxidase-mimicking DNAzyme was optimized to be used as a catalytic label in a stem-loop genosensor construction for quantifying the gene sequence Shiga-like toxin I of verotoxigenic E. coli. Experimental conditions such as pH, buffer composition, potassium ion concentration, and hemin-to-oligonucleotides ratio, were analyzed to maximize optical and electrochemical responses using microvolumes. Different stem-loop constructions were evaluated to obtain the optimum response against the target concentration. Linear ranges of 0.05-0.5 µM and limits of detection of 174 nM and 144 nM were estimated for the optical and electrochemical measurements, respectively. Selectivity was proved by assaying other verotoxigenic, enterotoxigenic and enteroinvasive sequences. The results show that, if a combination of small-volume electrochemical cells and low-cost untreated screen-printed electrodes with a relatively high geometric area is used, electrochemical measurements present similar sensitivity and limits of detection to the more usual optical ones, allowing the development of low-cost electrochemical biosensors based on the use of soluble DNAzymes as labels.

Impact of key deposition parameters on the morphology of silver foams prepared by dynamic hydrogen template deposition

The potentiostatic deposition of porous Ag foams from a new stable thiocyanate based bath using hydrogen bubbles as a dynamic template during deposition was investigated. The influence of the electrolyte content, deposition potential and deposition time on the micro- and nanoscale morphology of the Ag form was examined. The formation of three main morphological forms on the nanoscale level: dendrites, a framework of identical particles, and agglomerates of inhomogeneous particles with big Ag granules distributed on the foam surface, was demonstrated by the analysis of the scanning electron microscopy (SEM) data. The quality of the structures obtained was examined by energy dispersive X-ray spectroscopy (EDS) and X-ray diffractometry (XRD). It was found that the experimental parameters had a huge effect on the morphology of Ag on both the micro- and nanoscale. The structures with the most efficient geometry from the technological point of view were obtained with the correct combination of parameters, viz. high concentrations of NH 4 + and Ag + in conjunction with a sufficient deposition potential and time. Foams with roughness factors as high as 1100 were obtained, showing a high geometrical area normalized double-layer capacitance and relatively high gravimetric capacitance of 22 mF cm −2 and 2.4 F g −1, respectively.

Cold model test and industrial applications of high geometrical area packings for separation intensification

With a particular focus on the separation intensification of distillation and adsorption columns, this paper reports the hydrodynamic and mass transfer performance of four novel packings, characterized by wave-like corrugation angles, and specific geometric areas ranging up to 2000 m 2/m 3. The relation between specific geometrical area, pressure drop, capacity and separation efficiency are discussed as a function of gas and liquid loads. As expected with increasing specific geometrical area the efficiency increases significantly, however, this occurs at the cost of a corresponding decrease in capacity. The expected efficiency advantage could be exploited for separations intensification in pressure drop insensitive applications, as evidenced by the presented industrial examples of applications of the packings for distillation and stripping.

Catalytic combustion of coal mine ventilation air methane

Coal mine methane (CMM) is not only a greenhouse gas but also a wasted energy resource if not utilised. Underground coal mining is by far the most important source of fugitive mine methane, and approximately 70% of all coal mining related emissions are from underground ventilation air. Hence, research and development on mine methane capture, mitigation and utilisation should focus on methane emitted in ventilation air. To develop more efficient, cost effective technology for the mitigation and utilisation of mine ventilation air methane, this paper introduces the monolith catalyst bed reactor, which has better characteristics for power generation applications than fixed bed and fluidised bed reactors. This is due to its very low pressure drop at elevated mass throughputs, high geometrical area, and high mechanical strength and high resistance to dust. This paper briefly reviews methane catalytic combustion basics, and mainly presents experimental results on simulated ventilation air methane (VAM) catalytic combustion performance of four catalysts tested at different temperature, pressure and CH 4 concentrations. The experimental results show that determination of major operational parameters including temperature is very important for designing large-scale combustors to achieve high methane conversion rate. The major operational parameters determined in the experimental rig would be a reference for the design. In general, a preheated air temperature of ≥450 °C is required for the most effective of the four tested catalysts.

Liquid Holdup and Pressure Drop Determination in Structured Packing with CFD Simulations

AbstractIt is discussed how Computational Fluid Dynamics (CFD) can be used for hydrodynamics calculations within structured packings. Three dimensional (3D) simulations, in which the influence of mesh size and turbulence models were tested, have been carried out for dry pressure drop determination. Two dimensional (2D) Volume of Fluid gas‐liquid flow simulations have been used for liquid holdup determination. Numerical results are compared to tomographic liquid holdup measurements. Then, a comparison with data from a gas treatment pilot plant shows that wet pressure drop can be predicted by combining these two types of information (dry pressure drop and liquid holdup).