Eunsu Yang , Jinwon Choi , Gihan Kwon , Taejin Kim , Jaegeun Lee
{"title":"碳纳米管合成中双金属催化剂的逐步浸渍","authors":"Eunsu Yang , Jinwon Choi , Gihan Kwon , Taejin Kim , Jaegeun Lee","doi":"10.1016/j.apcata.2025.120568","DOIUrl":null,"url":null,"abstract":"<div><div>Supported bimetallic catalysts are widely used for carbon nanotube (CNT) synthesis, yet the effects of impregnation procedure remain underexplored. Here, we investigated how the sequence of metal impregnation affects CNT synthesis. We prepared cobalt-molybdenum (Co-Mo) bimetallic catalysts on alumina supports via co- and stepwise impregnation, then compared their CNT synthesis performance under identical conditions. Stepwise-impregnated catalysts exhibited higher carbon yields than those prepared by co-impregnation. Notably, impregnating Mo after Co achieved the highest yield despite the lowest BET surface area. Synchrotron X-ray diffraction and visible/UV-Raman spectroscopy revealed that only this catalyst contained Al<sub>2</sub>(MoO<sub>4</sub>)<sub>3</sub> with a MoO<sub>4</sub> structure. X-ray photoelectron spectroscopy clarified the surface chemistry: the catalyst with the highest CNT productivity exposed Mo entirely as Mo<sup>6 +</sup> in Al<sub>2</sub>(MoO<sub>4</sub>)<sub>3</sub> and CoMoO<sub>4</sub>, whereas the others contained both Mo<sup>4+</sup> and Mo<sup>6+</sup>. The MoO<sub>x</sub> species like Al<sub>2</sub>(MoO<sub>4</sub>)<sub>3</sub> is known to suppress Co sintering during CNT synthesis, delaying catalyst deactivation and enhancing the carbon yield. Moreover, an inverse relationship was observed between carbon yield and the CoMoO<sub>4</sub> content. This is attributed to the consumption of catalytically active Co during CoMoO<sub>4</sub> formation, which reduces active sites for CNT growth. ICP-OES further confirmed higher Co and Mo loadings for stepwise catalysts, contributing to superior catalyst performance. The extent of CoMoO<sub>4</sub> formation strongly depended on the metal introduction sequence. This trend is illustrated by considering the relationship between the point of zero charge of support and the pH of the metal precursor solutions.</div></div>","PeriodicalId":243,"journal":{"name":"Applied Catalysis A: General","volume":"708 ","pages":"Article 120568"},"PeriodicalIF":4.8000,"publicationDate":"2025-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Stepwise impregnation of bimetallic catalysts for carbon nanotube synthesis\",\"authors\":\"Eunsu Yang , Jinwon Choi , Gihan Kwon , Taejin Kim , Jaegeun Lee\",\"doi\":\"10.1016/j.apcata.2025.120568\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><div>Supported bimetallic catalysts are widely used for carbon nanotube (CNT) synthesis, yet the effects of impregnation procedure remain underexplored. Here, we investigated how the sequence of metal impregnation affects CNT synthesis. We prepared cobalt-molybdenum (Co-Mo) bimetallic catalysts on alumina supports via co- and stepwise impregnation, then compared their CNT synthesis performance under identical conditions. Stepwise-impregnated catalysts exhibited higher carbon yields than those prepared by co-impregnation. Notably, impregnating Mo after Co achieved the highest yield despite the lowest BET surface area. Synchrotron X-ray diffraction and visible/UV-Raman spectroscopy revealed that only this catalyst contained Al<sub>2</sub>(MoO<sub>4</sub>)<sub>3</sub> with a MoO<sub>4</sub> structure. X-ray photoelectron spectroscopy clarified the surface chemistry: the catalyst with the highest CNT productivity exposed Mo entirely as Mo<sup>6 +</sup> in Al<sub>2</sub>(MoO<sub>4</sub>)<sub>3</sub> and CoMoO<sub>4</sub>, whereas the others contained both Mo<sup>4+</sup> and Mo<sup>6+</sup>. The MoO<sub>x</sub> species like Al<sub>2</sub>(MoO<sub>4</sub>)<sub>3</sub> is known to suppress Co sintering during CNT synthesis, delaying catalyst deactivation and enhancing the carbon yield. Moreover, an inverse relationship was observed between carbon yield and the CoMoO<sub>4</sub> content. This is attributed to the consumption of catalytically active Co during CoMoO<sub>4</sub> formation, which reduces active sites for CNT growth. ICP-OES further confirmed higher Co and Mo loadings for stepwise catalysts, contributing to superior catalyst performance. The extent of CoMoO<sub>4</sub> formation strongly depended on the metal introduction sequence. This trend is illustrated by considering the relationship between the point of zero charge of support and the pH of the metal precursor solutions.</div></div>\",\"PeriodicalId\":243,\"journal\":{\"name\":\"Applied Catalysis A: General\",\"volume\":\"708 \",\"pages\":\"Article 120568\"},\"PeriodicalIF\":4.8000,\"publicationDate\":\"2025-09-12\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Applied Catalysis A: General\",\"FirstCategoryId\":\"1\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0926860X25004703\",\"RegionNum\":2,\"RegionCategory\":\"化学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"CHEMISTRY, PHYSICAL\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Applied Catalysis A: General","FirstCategoryId":"1","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0926860X25004703","RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
Stepwise impregnation of bimetallic catalysts for carbon nanotube synthesis
Supported bimetallic catalysts are widely used for carbon nanotube (CNT) synthesis, yet the effects of impregnation procedure remain underexplored. Here, we investigated how the sequence of metal impregnation affects CNT synthesis. We prepared cobalt-molybdenum (Co-Mo) bimetallic catalysts on alumina supports via co- and stepwise impregnation, then compared their CNT synthesis performance under identical conditions. Stepwise-impregnated catalysts exhibited higher carbon yields than those prepared by co-impregnation. Notably, impregnating Mo after Co achieved the highest yield despite the lowest BET surface area. Synchrotron X-ray diffraction and visible/UV-Raman spectroscopy revealed that only this catalyst contained Al2(MoO4)3 with a MoO4 structure. X-ray photoelectron spectroscopy clarified the surface chemistry: the catalyst with the highest CNT productivity exposed Mo entirely as Mo6 + in Al2(MoO4)3 and CoMoO4, whereas the others contained both Mo4+ and Mo6+. The MoOx species like Al2(MoO4)3 is known to suppress Co sintering during CNT synthesis, delaying catalyst deactivation and enhancing the carbon yield. Moreover, an inverse relationship was observed between carbon yield and the CoMoO4 content. This is attributed to the consumption of catalytically active Co during CoMoO4 formation, which reduces active sites for CNT growth. ICP-OES further confirmed higher Co and Mo loadings for stepwise catalysts, contributing to superior catalyst performance. The extent of CoMoO4 formation strongly depended on the metal introduction sequence. This trend is illustrated by considering the relationship between the point of zero charge of support and the pH of the metal precursor solutions.
期刊介绍:
Applied Catalysis A: General publishes original papers on all aspects of catalysis of basic and practical interest to chemical scientists in both industrial and academic fields, with an emphasis onnew understanding of catalysts and catalytic reactions, new catalytic materials, new techniques, and new processes, especially those that have potential practical implications.
Papers that report results of a thorough study or optimization of systems or processes that are well understood, widely studied, or minor variations of known ones are discouraged. Authors should include statements in a separate section "Justification for Publication" of how the manuscript fits the scope of the journal in the cover letter to the editors. Submissions without such justification will be rejected without review.