platinum surfaces
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Author(s):  
Ali Edalati-nejad ◽  
Sayyed Aboozar Fanaee ◽  
Maryam Ghodrat

Analysis of unsteady CH4/Air counterflow premixed flame into a newly designed plus-shaped channel is investigated in this study. The main objective is to explore the impact of platinum catalytic–coated walls of the combustion chamber on the flame characteristics and pollutant emissions. The OpenFOAM platform is used as a numerical simulation tool to investigate the effects of various equivalence ratios, from the range of lean to rich flames, and passing the reaction time on the counterflow flame characteristics and pollutant emissions of a plus-shaped chamber with the platinum catalyst–coated wall. Results show that the integrated temperature over the proposed geometry with platinum surfaces increases by 18% compared to the non-catalytic case. The numerical simulation revealed that presence of the platinum catalyst on the wall of the chamber has significant impact on reducing the pollutant emissions. This is evident as a 99.5% decrease on NO2 emission and a 58% reduction on CO2 formation are found.


2021 ◽  
Author(s):  
Axel Gross

It is a paradigm in chemistry that chemical reaction are mainly governed by thermodynamics. Within this assumption, reaction rates can be derived from transition state theory which requires a quasi-equilibrium between reactants and activated transition state complexes that is achieved through friction. However, to reach thermal equilibrium through friction takes some time. Here we show, based on ab initio molecular dynamics simulations of the interaction of molecular oxygen with stepped Pt surfaces, that chemical reactions in heterogeneous catalysis can occur in a non-equilibrium fashion when the excess kinetic energy upon entering the potential well of a reaction intermediate is large enough.


2021 ◽  
Vol MA2021-02 (49) ◽  
pp. 1464-1464
Author(s):  
Timo Fuchs ◽  
Jakub Drnec ◽  
Federico Calle-Vallejo ◽  
Natalie Stubb ◽  
Daniel Sandbeck ◽  
...  

2021 ◽  
Vol 7 (24) ◽  
pp. eabb1435
Author(s):  
Shiyi Wang ◽  
Enbo Zhu ◽  
Yu Huang ◽  
Hendrik Heinz

The oxygen reduction reaction (ORR) on platinum catalysts is essential in fuel cells. Quantitative predictions of the relative ORR activity in experiments, in the range of 1 to 50 times, have remained challenging because of incomplete mechanistic understanding and lack of computational tools to account for the associated small differences in activation energies (<2.3 kilocalories per mole). Using highly accurate molecular dynamics (MD) simulation with the Interface force field (0.1 kilocalories per mole), we elucidated the mechanism of adsorption of molecular oxygen on regular and irregular platinum surfaces and nanostructures, followed by local density functional theory (DFT) calculations. The relative ORR activity is determined by oxygen access to platinum surfaces, which greatly depends on specific water adlayers, while electron transfer occurs at a similar slow rate. The MD methods facilitate quantitative predictions of relative ORR activities of any platinum nanostructures, are applicable to other catalysts, and enable effective MD/DFT approaches.


2021 ◽  
Vol 103 (19) ◽  
Author(s):  
Peter A. Schultz ◽  
Harold P. Hjalmarson ◽  
Morgann Berg ◽  
Ezra Bussmann ◽  
David A. Scrymgeour ◽  
...  

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