Nitrogen-doped graphene electrocatalysts by thermal treatment applied to the oxygen reduction reaction: an electrochemical and chemometric investigation

Autor: Lima, Raquel Alves Corr??a, https://orcid.org/0000-0001-8000-0366
Přispěvatelé: Passos, Raimundo Ribeiro, Tanaka, Auro Atsushi, Farias, Marco Antonio dos Santos
Jazyk: portugalština
Rok vydání: 2021
Předmět:
Zdroj: Biblioteca Digital de Teses e Dissertações da UFAM
Universidade Federal do Amazonas (UFAM)
instacron:UFAM
Popis: Submitted by Raquel Lima (raquelalves_14@yahoo.com) on 2021-11-04T01:30:17Z No. of bitstreams: 4 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) DISSERTA????O RAQUEL ALVES CORR??A LIMA.pdf: 4879927 bytes, checksum: 98bd49708532e6f36e5be911b3c9f8ed (MD5) CARTA ENCAMINHAMENTO ASSINADA.pdf: 152565 bytes, checksum: 903fa74c728b8be0c2ffaa3843e32964 (MD5) ATA RAQUEL ALVES CORR??A LIMA.pdf: 277459 bytes, checksum: c1012bbd96a2d56e758e95905592a84b (MD5) Approved for entry into archive by PPGQ Qu??mica (ppgqsecretaria@gmail.com) on 2021-11-06T00:39:27Z (GMT) No. of bitstreams: 4 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) DISSERTA????O RAQUEL ALVES CORR??A LIMA.pdf: 4879927 bytes, checksum: 98bd49708532e6f36e5be911b3c9f8ed (MD5) CARTA ENCAMINHAMENTO ASSINADA.pdf: 152565 bytes, checksum: 903fa74c728b8be0c2ffaa3843e32964 (MD5) ATA RAQUEL ALVES CORR??A LIMA.pdf: 277459 bytes, checksum: c1012bbd96a2d56e758e95905592a84b (MD5) Approved for entry into archive by Divis??o de Documenta????o/BC Biblioteca Central (ddbc@ufam.edu.br) on 2021-11-06T19:58:08Z (GMT) No. of bitstreams: 4 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) DISSERTA????O RAQUEL ALVES CORR??A LIMA.pdf: 4879927 bytes, checksum: 98bd49708532e6f36e5be911b3c9f8ed (MD5) CARTA ENCAMINHAMENTO ASSINADA.pdf: 152565 bytes, checksum: 903fa74c728b8be0c2ffaa3843e32964 (MD5) ATA RAQUEL ALVES CORR??A LIMA.pdf: 277459 bytes, checksum: c1012bbd96a2d56e758e95905592a84b (MD5) Made available in DSpace on 2021-11-06T19:58:08Z (GMT). No. of bitstreams: 4 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) DISSERTA????O RAQUEL ALVES CORR??A LIMA.pdf: 4879927 bytes, checksum: 98bd49708532e6f36e5be911b3c9f8ed (MD5) CARTA ENCAMINHAMENTO ASSINADA.pdf: 152565 bytes, checksum: 903fa74c728b8be0c2ffaa3843e32964 (MD5) ATA RAQUEL ALVES CORR??A LIMA.pdf: 277459 bytes, checksum: c1012bbd96a2d56e758e95905592a84b (MD5) Previous issue date: 2021-05-28 Conselho Nacional de Desenvolvimento Cient??fico e Tecnol??gico - CNPq Nitrogen-doped graphene (N-graphene) has been extensively investigated as an electrocatalyst in the Oxygen Reduction Reaction (ORR) for application in the cathode of oxygen and hydrogen supplied polymer electrolyte membrane fuel cells. Doping can be achieved by thermal treatment, a simple and easily scalable method, however, the conditions employed may affect N-graphene???s electrocatalytic activity. In this work, a central composite design was adopted to evaluate the effect of thermal treatment temperature (varied from 660 ??C to 940 ??C) and of the mass ratio of graphene and urea precursors (respectively varied from 1:3 to 1:17), on the electron transfer number (n) of the ORR electrocatalyzed in alkaline medium by the prepared N-graphene, and to determine the factor levels in which this response is maximized. There was no interaction effect between the factors, and only the temperature had a positive and statistically significant effect on ORR???s n value. The optimal doping condition was at 940 ??C, in any of the studied mass ratios. With N-graphene prepared at this temperature, ORR exhibited n = 4, an onset potential of 0.798 V vs RHE, a half-wave potential of 0.689 V vs RHE, a kinetic current density of -4.01 mA mg-1 and a Tafel slope of 75.53 mV dec-1. This investigation represents an important step in the adoption of multivariate experimentation for the exploration of metal-free electrocatalysts for fuel cell cathodes. O grafeno dopado com nitrog??nio (N-grafeno) tem sido foco de intensa investiga????o como eletrocatalisador na Rea????o de Redu????o de Oxig??nio (RRO) para aplica????o final no c??todo de c??lulas a combust??vel de membrana de eletr??lito polim??rico supridas com oxig??nio e hidrog??nio. A dopagem pode ser realizada por meio de tratamento t??rmico, um m??todo simples e facilmente adapt??vel ?? escala industrial, no entanto, as condi????es empregadas podem afetar a atividade eletrocatal??tica do N-grafeno. Neste trabalho, um planejamento composto central foi adotado para avaliar o efeito da temperatura do tratamento t??rmico (variada de 660 ??C a 940 ??C) e da propor????o em massa dos precursores grafeno e ureia (respectivamente, variada de 1:3 a 1:17), sobre o n??mero de transfer??ncia eletr??nica (n) da RRO eletrocatalisada em meio b??sico pelo N-grafeno preparado, e para determinar os n??veis dos fatores nos quais essa resposta ?? maximizada. N??o houve efeito de intera????o entre os fatores e apenas a temperatura exerceu um efeito estatisticamente significativo, e tamb??m positivo, sobre o n da RRO. A condi????o ??tima de dopagem foi a 940 ??C, em qualquer uma das propor????es estudadas. Com o N-grafeno preparado nessa temperatura, a RRO exibiu n = 4, potencial de in??cio de 0,798 V vs ERH, potencial de meia-onda de 0,689 V vs ERH, densidade de corrente cin??tica de -4,01 mA mg-1 e coeficiente angular de Tafel de 75,53 mV d??c-1. A melhoria na resposta eletrocatal??tica pode estar associada a um maior teor de N-pirr??lico, o qual ?? favorecido com o aumento da temperatura de dopagem. Essa investiga????o representa um passo importante na ado????o da experimenta????o multivariada para a explora????o de eletrocatalisadores n??o met??licos para o c??todo de c??lulas a combust??vel.
Databáze: OpenAIRE
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