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Highly active Pt 3 Rh/C nanoparticles towards ethanol electrooxidation. Influence of the catalyst structure

Highly active Pt 3 Rh/C nanoparticles towards ethanol electrooxidation. Influence of the catalyst structure
Highly active Pt 3 Rh/C nanoparticles towards ethanol electrooxidation. Influence of the catalyst structure

The electrochemical oxidation of ethanol results in the formation of strongly adsorbed intermediates. Pt–Rh catalysts are proposed as alternatives since they easy the C[sbnd]C bond breaking. However, the effect of the Pt–Rh structure on the catalytic activity and selectivity to CO 2 is not well understood. Here, we synthesised Pt/C and two different Pt–Rh/C catalyst architectures, an alloy (Pt 3 Rh/C)and a bimetallic mixture (Pt 3 –Rh/C)to study the effect of catalyst structure on its catalytic activity and on the products formed during the ethanol oxidation in acid media. The nanoparticles were prepared by a modified polyol reduction method using ethylene glycol as a co-reducing agent and Pb as a material of sacrifice, to obtain very small and well-dispersed nanoparticles on the carbon support. Fourier transform infrared spectroscopy and derivative voltammetry was used to give insights about the ethanol oxidation mechanism occurring at the developed catalysts. The samples characterised by X-ray diffraction analysis showed distortions in the Pt lattice parameters for the Pt-Rh alloy structure due to the presence of Rh in the catalyst's composition. Transmission electron microscopy analyses indicate that nanoparticles were well-dispersed on a carbon support, with spherical shapes and small particle sizes (2–3 nm). in situ X-ray absorption spectroscopy data evidence that Pt–Rh interactions produce changes in the Pt 5d band vacancy. The electronic effect is maximized when Pt forms an alloy with Rh, resulting in the highest d-band vacancy of the Pt 3 Rh/C. The Pt 3 Rh/C catalyst showed the highest activity towards ethanol oxidation, presenting current densities in a quasi-steady-state condition (measured at 600 mV)around 5.2 times higher than the commercial Pt/C (Alfa Aesar). Moreover, the onset potential for ethanol oxidation shifts to more negative potentials (110 mV lower taken at 1 mA cm –2 )was also observed. In situ FTIR data revealed that Pt/C catalyst favours the formation of acetic acid. The synergistic effect between Rh and the alloy structure results in an easier C[sbnd]C bond breaking for Pt 3 Rh/C, in comparison to Pt 3 –Rh mixture, thus favouring CO 2 formation at lower potentials.

Electrochemical oxidation of ethanol, Fuel cells, In situ FTIR, Pt–Rh catalyst
0926-3373
113-127
Almeida, Caio V.S.
718ae32a-23a1-4a8d-8248-a66d6f96f5fc
Ferreira, Dênis S.
98f473c6-def9-4f7c-8a3e-a5de618d01f4
Huang, Haoliang
132a8eda-b800-4fa7-9583-6b4306f30247
Gaiotti, Ana C.
ce8e96b1-f7f4-48a1-845d-99c5bbe348a3
Camara, Giuseppe A.
031f79b0-423a-4fed-bd18-e5a40061d5cc
Russell, Andrea E.
b6b7c748-efc1-4d5d-8a7a-8e4b69396169
Eguiluz, Katlin I.B.
59d40318-d101-44e0-b00c-b8f30aa1baf4
Salazar-Banda, Giancarlo R.
80800367-cb82-42ad-8137-83e98dbf4ecb
Almeida, Caio V.S.
718ae32a-23a1-4a8d-8248-a66d6f96f5fc
Ferreira, Dênis S.
98f473c6-def9-4f7c-8a3e-a5de618d01f4
Huang, Haoliang
132a8eda-b800-4fa7-9583-6b4306f30247
Gaiotti, Ana C.
ce8e96b1-f7f4-48a1-845d-99c5bbe348a3
Camara, Giuseppe A.
031f79b0-423a-4fed-bd18-e5a40061d5cc
Russell, Andrea E.
b6b7c748-efc1-4d5d-8a7a-8e4b69396169
Eguiluz, Katlin I.B.
59d40318-d101-44e0-b00c-b8f30aa1baf4
Salazar-Banda, Giancarlo R.
80800367-cb82-42ad-8137-83e98dbf4ecb

Almeida, Caio V.S., Ferreira, Dênis S., Huang, Haoliang, Gaiotti, Ana C., Camara, Giuseppe A., Russell, Andrea E., Eguiluz, Katlin I.B. and Salazar-Banda, Giancarlo R. (2019) Highly active Pt 3 Rh/C nanoparticles towards ethanol electrooxidation. Influence of the catalyst structure. Applied Catalysis B: Environmental, 254, 113-127. (doi:10.1016/j.apcatb.2019.04.078).

Record type: Article

Abstract

The electrochemical oxidation of ethanol results in the formation of strongly adsorbed intermediates. Pt–Rh catalysts are proposed as alternatives since they easy the C[sbnd]C bond breaking. However, the effect of the Pt–Rh structure on the catalytic activity and selectivity to CO 2 is not well understood. Here, we synthesised Pt/C and two different Pt–Rh/C catalyst architectures, an alloy (Pt 3 Rh/C)and a bimetallic mixture (Pt 3 –Rh/C)to study the effect of catalyst structure on its catalytic activity and on the products formed during the ethanol oxidation in acid media. The nanoparticles were prepared by a modified polyol reduction method using ethylene glycol as a co-reducing agent and Pb as a material of sacrifice, to obtain very small and well-dispersed nanoparticles on the carbon support. Fourier transform infrared spectroscopy and derivative voltammetry was used to give insights about the ethanol oxidation mechanism occurring at the developed catalysts. The samples characterised by X-ray diffraction analysis showed distortions in the Pt lattice parameters for the Pt-Rh alloy structure due to the presence of Rh in the catalyst's composition. Transmission electron microscopy analyses indicate that nanoparticles were well-dispersed on a carbon support, with spherical shapes and small particle sizes (2–3 nm). in situ X-ray absorption spectroscopy data evidence that Pt–Rh interactions produce changes in the Pt 5d band vacancy. The electronic effect is maximized when Pt forms an alloy with Rh, resulting in the highest d-band vacancy of the Pt 3 Rh/C. The Pt 3 Rh/C catalyst showed the highest activity towards ethanol oxidation, presenting current densities in a quasi-steady-state condition (measured at 600 mV)around 5.2 times higher than the commercial Pt/C (Alfa Aesar). Moreover, the onset potential for ethanol oxidation shifts to more negative potentials (110 mV lower taken at 1 mA cm –2 )was also observed. In situ FTIR data revealed that Pt/C catalyst favours the formation of acetic acid. The synergistic effect between Rh and the alloy structure results in an easier C[sbnd]C bond breaking for Pt 3 Rh/C, in comparison to Pt 3 –Rh mixture, thus favouring CO 2 formation at lower potentials.

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Accepted/In Press date: 22 April 2019
e-pub ahead of print date: 24 April 2019
Published date: 5 October 2019
Keywords: Electrochemical oxidation of ethanol, Fuel cells, In situ FTIR, Pt–Rh catalyst

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Local EPrints ID: 431670
URI: http://eprints.soton.ac.uk/id/eprint/431670
ISSN: 0926-3373
PURE UUID: 773d95da-ad51-4526-9203-dd9eed42f320
ORCID for Andrea E. Russell: ORCID iD orcid.org/0000-0002-8382-6443

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Date deposited: 12 Jun 2019 16:30
Last modified: 07 Oct 2020 06:33

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Contributors

Author: Caio V.S. Almeida
Author: Dênis S. Ferreira
Author: Haoliang Huang
Author: Ana C. Gaiotti
Author: Giuseppe A. Camara
Author: Katlin I.B. Eguiluz
Author: Giancarlo R. Salazar-Banda

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