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对多壁碳纳米管的结构和组成进行精细调控提高其电催化氧还原反应制H2O2的催化活性 认领

Enhanced electrocatalytic activity for H2O2 production by the oxygen reduction reaction:Rational control of the structure and composition of multi-walled carbon nanotubes
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摘要 双氧水(H2O2)是一种重要的化工原料.目前,其工业生产主要采用蒽醌法,但工艺复杂、能耗高,同时高浓度H2O2不宜储存和远距离运输.电催化氧气二电子还原(ORR)制备H2O2技术具有绿色环保、工艺简单等优点,且可实现H2O2的原位生产,受到了广泛关注.开发高效、廉价的非贵金属催化剂是ORR制备H2O2技术的关键.多壁碳纳米管(MWCNTs)作为一种便宜易得、稳定环保的常用催化材料,具有一定的ORR催化活性,本文对MWCNTs进行表面氧化处理,通过优化氧化处理的条件调控其结构和表面的含氧官能团含量,提高MWCNTs电催化ORR制H2O2的性能.物化表征结果表明,随着氧化处理温度的上升或时间的延长,MWCNTs的结构从外到内逐渐被破坏,管壁表面对2e–路径ORR具有催化活性的缺陷和含氧官能团含量逐渐增加.但随着氧化程度进一步加深,MWCNTs的管壁被严重破坏,材料导电能力显著降低,从而不利于电催化ORR的进行.电化学测试结果表明,在所有的氧化MWCNTs样品中,O-CNTs-40-1(40℃,氧化处理1h)电流最大,相比未经处理的商业化MWCNTs的ORR起始还原电位正移最明显.而且催化ORR制H2O2的选择性提升幅度也最大,其中双氧水产率从约30%提升至50%左右,反应转移电子数则从3.4降低至3.0.电化学阻抗谱结果表明,O-CNTs-40-1具有最佳导电能力.将O-CNTs-40-1负载到聚四氟乙烯处理过的碳纸(CP)上作为电极,用于0.1molL^-1KOH溶液中电催化ORR生成H2O2的实验结果显示,恒电位0.46V(vs.RHE)40min,CP@O-CNTs-40-1电极的H2O2累积浓度为64.8mgL^-1,而CP@MWCNTs电极对应的浓度仅为39.4mgL^-1.且CP@O-CNTs-40-1电极在H2O2累积过程中对应的电流效率达到52%–65%.这表明比未经调控的MWCNTs,经过精准调控结构和组成之后的O-CNTs-40-1更加适合用作电催化ORR原位制备H2O2的催化剂.通过精确调控结构和组成之后,MWCNTs外层断裂腐蚀而内层结构完好,使其同时具备足够的催化 Hydrogen peroxide(H2O2)is a very useful chemical reagent,but the current industrial methods for its production suffer from serious energy consumption problems.Using high-activity and high-selectivity catalysts to electrocatalyze the oxygen reduction reaction(ORR)through a two-electron(2e^-)pathway is a very promising route to produce H2O2.In this work,we obtained partially oxidized multi-walled carbon nanotubes(MWCNTs)with controlled structure and composition by oxidation with concentrated sulfate and potassium permanganate at 40℃ for 1 h(O-CNTs-40-1).The outer layers of O-CNTs-40-1 are damaged with defects and oxygen-containing functional groups,while the inner layers are maintained intact.The optimized structure and composition of the partially oxidized MWCNTs ensure that O-CNTs-40-1 possesses both a sufficient number of catalytic sites and good conductivity.The results of rotating ring disk electrode measurements reveal that,among all oxidized MWCNTs,O-CNTs-40-1 shows the greatest improvement in hydrogen peroxide selectivity(from ~ 30% to ~ 50%)and electron transfer number(from ~ 3.4 to ~ 3.0)compared to those of the raw MWCNTs.The results of electrochemical impedance spectroscopy measurements indicate that both the charge-transfer and intrinsic resistances of O-CNTs-40-1 are lower than those of the raw MWCNTs and of the other oxidized MWCNTs.Finally,direct tests of the H2O2 production confirm the greatly improved catalytic activity of O-CNTs-40-1 relative to that of the raw MWCNTs.
作者 王毅 易秘 王昆 宋树芹 Yi Wang;Mi Yi;Kun Wang;Shuqin Song(The Key Lab of Low-carbon Chemistry & Energy Conservation of Guangdong Province,School of Chemical Engineering and Technology,Sun Yat-sen University,Zhuhai 519082,Guangdong,China;School of Materials Science and Engineering,Sun Yat-sen University,Guangzhou 510275,Guangdong,China)
出处 《催化学报》 SCIE EI CAS CSCD 北大核心 2019年第4期523-533,M0003共12页 Chinese Journal of Catalysis
基金 国家自然科学基金(21576299,21576300) 广州科技计划项目(201607010104,201707010079) 广东省省级科技计划项目(2017A050501009) 国家重点研发计划(2016YFB0101204) 广东省高层次人才特殊支持计划项目(2016TQ03N322) 高校基本科研业务费青年教师重点培育项目(17lgzd14).
关键词 过氧化氢 氧还原反应 多壁碳纳米管 电催化性能 氧化处理 Hydrogen peroxide Oxygen reduction reaction Multi-walled carbon nanotubes Electrocatalytic activity Oxidation treatment
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