{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,9]],"date-time":"2025-12-09T11:35:44Z","timestamp":1765280144898,"version":"build-2065373602"},"reference-count":38,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2020,2,17]],"date-time":"2020-02-17T00:00:00Z","timestamp":1581897600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","doi-asserted-by":"publisher","award":["POCI-01-0145-FEDER-016422","UID\/EQU\/50020\/2019","IF\/01080\/2015"],"award-info":[{"award-number":["POCI-01-0145-FEDER-016422","UID\/EQU\/50020\/2019","IF\/01080\/2015"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["J. Compos. Sci."],"abstract":"<jats:p>The oxygen reduction reaction is an essential reaction in several energy conversion devices such as fuel cells and batteries. So far, the best performance is obtained by using platinum-based electrocatalysts, which make the devices really expensive, and thus, new and more affordable materials should be designed. Biomass-derived carbons were prepared by hydrothermal carbonization in the presence of carbon nanotubes with different oxygen surface functionalities to evaluate their effect on the final properties. Additionally, nitrogen functional groups were also introduced by ball milling the carbon composite together with melamine. The oxygen groups on the surface of the carbon nanotubes favor their dispersion into the precursor mixture and the formation of a more homogenous carbon structure with higher mechanical strength. This type of structure partially avoids the crushing of the nanotubes and the carbon spheres during the ball milling, resulting in a carbon composite with enhanced electrical conductivity. Undoped and N-doped composites were used as electrocatalysts for the oxygen reduction reaction. The onset potential increases by 20% due to the incorporation of carbon nanotubes (CNTs) and nitrogen, which increases the number of active sites and improves the chemical reactivity, while the limiting current density increases by 47% due to the higher electrical conductivity.<\/jats:p>","DOI":"10.3390\/jcs4010020","type":"journal-article","created":{"date-parts":[[2020,2,19]],"date-time":"2020-02-19T04:06:01Z","timestamp":1582085161000},"page":"20","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":12,"title":["Hydrothermal Carbon\/Carbon Nanotube Composites as Electrocatalysts for the Oxygen Reduction Reaction"],"prefix":"10.3390","volume":"4","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9046-5933","authenticated-orcid":false,"given":"Rafael G.","family":"Morais","sequence":"first","affiliation":[{"name":"Associate Laboratory LSRE-LCM, Departamento de Engenharia Qu\u00edmica, Faculdade de Engenharia, Universidade do Porto, R. Dr Roberto Frias s\/n, 4200-465 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5003-0035","authenticated-orcid":false,"given":"Natalia","family":"Rey-Raap","sequence":"additional","affiliation":[{"name":"Associate Laboratory LSRE-LCM, Departamento de Engenharia Qu\u00edmica, Faculdade de Engenharia, Universidade do Porto, R. Dr Roberto Frias s\/n, 4200-465 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1539-7763","authenticated-orcid":false,"given":"Rui S.","family":"Costa","sequence":"additional","affiliation":[{"name":"REQUIMTE\/LAQV, Departamento de Qu\u00edmica e Bioqu\u00edmica, Faculdade de Ci\u00eancias, Universidade do Porto, 4169-007 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9224-1917","authenticated-orcid":false,"given":"Clara","family":"Pereira","sequence":"additional","affiliation":[{"name":"REQUIMTE\/LAQV, Departamento de Qu\u00edmica e Bioqu\u00edmica, Faculdade de Ci\u00eancias, Universidade do Porto, 4169-007 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6397-3713","authenticated-orcid":false,"given":"Alexandra","family":"Guedes","sequence":"additional","affiliation":[{"name":"Departamento de Geoci\u00eancias, Ambiente e Ordenamento do Territ\u00f3rio, Faculdade de Ci\u00eancias, Universidade do Porto, 4169-007 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0395-8199","authenticated-orcid":false,"given":"Jos\u00e9 L.","family":"Figueiredo","sequence":"additional","affiliation":[{"name":"Associate Laboratory LSRE-LCM, Departamento de Engenharia Qu\u00edmica, Faculdade de Engenharia, Universidade do Porto, R. Dr Roberto Frias s\/n, 4200-465 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5447-2471","authenticated-orcid":false,"given":"M. Fernando R.","family":"Pereira","sequence":"additional","affiliation":[{"name":"Associate Laboratory LSRE-LCM, Departamento de Engenharia Qu\u00edmica, Faculdade de Engenharia, Universidade do Porto, R. Dr Roberto Frias s\/n, 4200-465 Porto, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2020,2,17]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"114027","DOI":"10.1016\/j.apenergy.2019.114027","article-title":"Recent progress of carbon dots and carbon nanotubes applied in oxygen reduction reaction of fuel cell for transportation","volume":"257","author":"Mohideen","year":"2020","journal-title":"Appl. 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