Search

Your search keyword '"Vavra, Jan"' showing total 4 results
Start Over Author "Vavra, Jan" Topic electrocatalysts
4 results on '"Vavra, Jan"'

1. Real‐time Monitoring Reveals Dissolution/Redeposition Mechanism in Copper Nanocatalysts during the Initial Stages of the CO2 Reduction Reaction.

Author

Vavra, Jan, Shen, Tzu‐Hsien, Stoian, Dragos, Tileli, Vasiliki, and Buonsanti, Raffaella

Subjects
*COPPER oxide, *TRANSMISSION electron microscopy, *COPPER, *ELECTROLYTIC reduction, *X-ray absorption, *X-ray microscopy, *ELECTROCATALYSTS
Abstract

Size, morphology, and surface sites of electrocatalysts have a major impact on their performance. Understanding how, when, and why these parameters change under operating conditions is of importance for designing stable, active, and selective catalysts. Herein, we study the reconstruction of a Cu‐based nanocatalysts during the startup phase of the electrochemical CO2 reduction reaction by combining results from electrochemical in situ transmission electron microscopy with operando X‐ray absorption spectroscopy. We reveal that dissolution followed by redeposition, rather than coalescence, is the mechanism responsible for the size increase and morphology change of the electrocatalyst. Furthermore, we point out the key role played by the formation of copper oxides in the process. Understanding of the underlying processes opens a pathway to rational design of Cu electro (re)deposited catalysts and to stability improvement for catalysts fabricated by other methods. [ABSTRACT FROM AUTHOR]

Published
2021
Full Text
View/download PDF

2. Stability and Degradation Mechanisms of Copper‐Based Catalysts for Electrochemical CO2 Reduction.

Author

Popović, Stefan, Smiljanić, Milutin, Jovanovič, Primož, Vavra, Jan, Buonsanti, Raffaella, and Hodnik, Nejc

Subjects
ELECTROLYTIC reduction, CATALYSTS, ELECTROLYSIS, COPPER
Abstract

To date, copper is the only monometallic catalyst that can electrochemically reduce CO2 into high value and energy‐dense products, such as hydrocarbons and alcohols. In recent years, great efforts have been directed towards understanding how its nanoscale structure affects activity and selectivity for the electrochemical CO2 reduction reaction (CO2RR). Furthermore, many attempts have been made to improve these two properties. Nevertheless, to advance towards applied systems, the stability of the catalysts during electrolysis is of great significance. This aspect, however, remains less investigated and discussed across the CO2RR literature. In this Minireview, the recent progress on understanding the stability of copper‐based catalysts is summarized, along with the very few proposed degradation mechanisms. Finally, our perspective on the topic is given. [ABSTRACT FROM AUTHOR]

Published
2020
Full Text
View/download PDF

3. Oxygen Evolution Reaction in Ba0.5Sr0.5Co0.8Fe0.2O3-delta Aided by Intrinsic Co/Fe Spinel-Like Surface

Author

Shen, Tzu-Hsien, Spillane, Liam, Vavra, Jan, Thi Ha My Pham, Peng, Jiayu, Shao-Horn, Yang, and Tileli, Vasiliki

Subjects
reconstruction, x-ray-diffraction, water oxidation, behaviors, catalysis, transition-metal oxides, cobalt, absorption, electrocatalysts, perovskite
Abstract

Among the perovskites used to catalyze the oxygen evolution reaction (OER), Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) exhibits excellent activity which is thought to be related to dynamic reconstruction at the flexible perovskite surface due to accommodation of large amount of oxygen vacancies. By studying the local structure and chemistry of BSCF surfaces, in detail, via a range of transmission electron microscopy (TEM) methods, we show that the surfaces of the as-synthesized BSCF particles are Co/Fe rich, and remarkably, adopt a spinel-like structure with a reduced valence of Co ions. Post-mortem and identical location TEM analyses reveal that the Co/Fe spinel-like surface retains a stable chemical environment of the Co/Fe ions, although its structure weakens after electrochemical processing. Further, it is verified that prior to the onset of OER, the Co/Fe spinel-like surface promotes the formation of the highly active Co(Fe)OOH phase, which enhances the OER electrocatalytic properties of the underlying conductive BSCF perovskite. This study provides a detailed understanding of the fundamental transformations that oxide catalysts undergo during electrochemical processes and can aid in the development of novel oxide catalysts with enhanced activity.

4. Stability and Degradation Mechanisms of Copper-Based Catalysts for Electrochemical CO2 Reduction

Author

Popovic, Stefan, Smiljanic, Milutin, Jovanovic, Primoz, Vavra, Jan, Buonsanti, Raffaella, and Hodnik, Nejc

Subjects
copper nanoparticles, electrochemical co2 reduction, stability, insights, electrocatalysts, electroreduction, cathodic corrosion, in-situ, gold catalyst, nanocrystals, carbon-dioxide reduction, ethylene, electron-microscopy, cu, degradation
Abstract

To date, copper is the only monometallic catalyst that can electrochemically reduce CO2 into high value and energy-dense products, such as hydrocarbons and alcohols. In recent years, great efforts have been directed towards understanding how its nanoscale structure affects activity and selectivity for the electrochemical CO2 reduction reaction (CO2RR). Furthermore, many attempts have been made to improve these two properties. Nevertheless, to advance towards applied systems, the stability of the catalysts during electrolysis is of great significance. This aspect, however, remains less investigated and discussed across the CO2RR literature. In this Minireview, the recent progress on understanding the stability of copper-based catalysts is summarized, along with the very few proposed degradation mechanisms. Finally, our perspective on the topic is given.

Catalog

Books, media, physical & digital resources
See catalog results