Catalytic flow with a coupled Finite Difference -- Lattice Boltzmann scheme

Many catalyst devices employ flow through porous structures, which leads to a complex macroscopic mass and heat transport. To unravel the detailed dynamics of the reactive gas flow, we present an all-encompassing model, consisting of thermal lattice Boltzmann model by Kang et al., used to solve the heat and mass transport in the gas domain, coupled to a finite differences solver for the heat equation in the solid via thermal reactive boundary conditions for a consistent treatment of the reaction enthalpy. The chemical surface reactions are incorporated in a flexible fashion through flux boundary conditions at the gas-solid interface. We scrutinize the thermal FD-LBM by benchmarking the macroscopic transport in the gas domain as well as conservation of the enthalpy across the solid-gas interface. We exemplify the applicability of our model by simulating the reactive gas flow through a microporous material catalysing the so-called water-gas-shift reaction

Catalytic flow with a coupled finite difference — Lattice Boltzmann scheme

Many catalyst devices employ flow through porous structures, which leads to a complex macroscopic mass and heat transport. To unravel the detailed dynamics of the reactive gas flow, we present an all-encompassing model, consisting of thermal lattice Boltzmann model by Kang et al., used to solve the heat and mass transport in the gas domain, coupled to a finite differences solver for the heat equation in the solid via thermal reactive boundary conditions for a consistent treatment of the reaction enthalpy. The chemical surface reactions are incorporated in a flexible fashion through flux boundary conditions at the gas–solid interface. We scrutinize the thermal FD-LBM by benchmarking the macroscopic transport in the gas domain as well as conservation of the enthalpy across the solid–gas interface. We exemplify the applicability of our model by simulating the reactive gas flow through a microporous material catalyzing the so-called water-gas-shift reaction

Сучасні продукти функціонального призначення з додаванням рослинної сировини

Результатами аналізу останніх досліджень та публікацій підтверджено гіпотезу доцільності розроблення рецептури функціональних риборослинних пресервів на основі бичка азовського та гливи звичайної

Pt Sub-Monolayer on Au: System Stability and Insights into Platinum Electrochemical Dissolution

Platinum is the best single element oxygen reduction reaction electrocatalyst. In recent years, several advanced catalysts have been suggested. One of them is the so-called “platinum monolayer electrocatalyst”. In this work we demonstrate the potential- and time-resolved dissolution characteristics of such sub-monolayer platinum supported on gold in potentiodynamic and potentiostatic regimes. It is shown that the as-prepared Pt@Au is not stable, but rather shows significant dissolution of both Pt and Au similar to the pure elements. Potential-resolved dissolution profiles reveal that anodic dissolution scales with Pt coverage, while cathodic dissolution and quasi-steady-state dissolution are Pt coverage independent. This implies a significantly higher Pt coverage normalized dissolution of Pt@Au, viz. a factor of four higher dissolution amounts for Pt coverage of 0.25. The onsets of Pt and Au dissolution are also comparable to the pure elements. Only after intermixing during potential cycling does the system become somewhat stabilized. The onset of Pt transient anodic dissolution shifts to more positive values. The data obtained in the current work provide new insights into the mechanism of platinum dissolution. It also aids the understanding of the previously observed effect of stabilization of Pt catalysts by addition of Au, and will therefore guide future developments for improving catalyst performance

On the Time Resolution of Electrochemical Scanning Flow Cell Coupled to Downstream Analysis

Many of the recent advancements in the electrocatalysis research have been obtained by application of coupled electrochemistry/mass-spectrometry techniques. Representative example is the electrochemical flow cells coupled to inductively coupled plasma mass spectrometry (on-line ICP-MS) in electrocatalysis stability research. In this technique, unambiguous correlation of the concentration of dissolved species vs. potential/current represents a significant challenge due to different time scales of electrochemical and concentration transients. In this work, we address this issue by investigating the time resolution of the scanning flow cell (SFC). For this, residence time distribution (RTD) is estimated using Cu dissolution experiments. Both experiments and numerical simulations show that RTD can be closely approximated by a bi-Gaussian distribution with asymmetry arising from the mass transport of species in the outlet channel. Studying the influence of cell geometry and experimental conditions on RTD, it is found that the length of the outlet tubes of SFC should be as short as possible. Moreover, an optimum flow rate and angle between inlet and outlet channels are defined. To demonstrate practical applicability of our findings, obtained RTD was used to deconvolute previously reported platinum dissolution transients during cycling voltammetry. Such data are of high importance in mechanistic studies of platinum dissolution. (C) 2019 The Electrochemical Society

Catalytic flow with a coupled finite difference — Lattice Boltzmann scheme

Many catalyst devices employ flow through porous structures, which leads to a complex macroscopic mass and heat transport. To unravel the detailed dynamics of the reactive gas flow, we present an all-encompassing model, consisting of thermal lattice Boltzmann model by Kang et al., used to solve the heat and mass transport in the gas domain, coupled to a finite differences solver for the heat equation in the solid via thermal reactive boundary conditions for a consistent treatment of the reaction enthalpy. The chemical surface reactions are incorporated in a flexible fashion through flux boundary conditions at the gas–solid interface. We scrutinize the thermal FD-LBM by benchmarking the macroscopic transport in the gas domain as well as conservation of the enthalpy across the solid–gas interface. We exemplify the applicability of our model by simulating the reactive gas flow through a microporous material catalyzing the so-called water-gas-shift reaction

Nanoporous Pt@Au_<i>x</i>Cu_{100–<i>x</i>} by Hydrogen Evolution Assisted Electrodeposition of Au_<i>x</i>Cu_{100–<i>x</i>} and Galvanic Replacement of Cu with Pt: Electrocatalytic Properties

Electrodeposition of high-surface-area nanoporous Au–Cu foams under conditions of hydrogen codeposition is studied. The honeycomb-like Au_<i>x</i>Cu_{100–<i>x</i>} foams with 0 ≤ <i>x</i> ≤ 100 are electrodeposited by controlling the amount of corresponding ions in the solution. The amount of metal ions in deposited films follows that in used electrolytes. Compared to monometallic foams, the Au_<i>x</i>Cu_{100–<i>x</i>} structures are characterized by smaller ligament or particle sizes (less than 10 nm) and improved stability. The addition of even a small amount of Cu to the Au matrix is found to dramatically improve the stability of the structure in air environment or an acidic medium. Pt@Au_<i>x</i>Cu_{100–<i>x</i>} structures are formed by the galvanic displacement of Cu from Au_<i>x</i>Cu_{100–<i>x</i>} templates. During the displacement of Cu by Pt, Au serves as a buffer, decreasing mechanical stresses and preventing the detachment of the foam from the substrate. The surface ratio of Pt to Au atoms is controlled by adjusting the amount of Cu in the template. Pt@Au_<i>x</i>Cu_{100–<i>x</i>} electrodes are investigated as novel electrocatalysts for methanol oxidation in alkaline media. The Au-enriched surfaces show higher catalytic activity toward methanol oxidation, while the electrodes with a higher amount of Pt are more stable