摘要
近年来,工业化的高速推进和化石燃料的大量消耗,不仅造成严重的温室效应,而且加剧了能源危机和环境恶化等问题.电催化CO_(2)还原技术可将温室气体CO_(2)转化为具有经济价值的小分子化合物,且可以耦合间歇性可再生能源(如太阳能、风能、潮汐能等)产生的电力,目前已成为实现碳中和目标最有前景的技术途径之一.然而,由于CO_(2)分子化学惰性较强,需要较高的过电位才能将其活化,导致其转化效率低.铋作为一种无毒无害、价格低廉且具有较高析氢过电位的非贵金属材料,可有效地促进CO_(2)电还原为甲酸.但受质量活性、稳定性和产率的限制,铋基催化剂目前仍难以实现工业化应用.本文采用静电纺丝技术结合热处理方法制备了碳层封装的超小铋纳米颗粒,并用于二氧化碳电还原制甲酸.透射电镜等表征结果表明,铋纳米颗粒均匀地分散于碳纳米纤维中.电化学测试结果表明,在900℃下煅烧2 h制得的Bi/CNFs-900催化剂具有较好的电还原CO_(2)为甲酸的性能.在较宽的电化学窗口内,甲酸的法拉第效率均在90%以上,在-1.20 V vs.RHE的电位下实现了-232.2 mA cm^(-2)的电流密度.该催化剂表现出较高的质量活性(-1.6 A mg-_(Bi)^(-1))和较高的甲酸产率(29.8 mol h^(-1)cm^(-2)g^(-1)),分别是纯铋颗粒质量活性(-0.23 A mg-_(Bi)^(-1))的7.05倍,甲酸产率(4.2 mol h^(-1)cm^(-2)g^(-1))的7.07倍.密度泛函理论计算与原位拉曼光谱结果表明,Bi/CNFs-900能够有效地降低关键中间体*OCHO的吉布斯自由能垒.Bi/CNFs-900具有较好的催化活性和选择性的主要原因为:(1)热解过程中碳纤维对铋纳米颗粒的迁移起到一定限制作用,使得更多的活性位点得以暴露,同时大大降低了金属的实际负载量;(2)铋与周围的碳层存在静电相互作用,可以有效地降低界面电荷的转移电阻,促进电子的快速转移;(3)碳纤维的限域作用也有效地抑制了催化反�
Electrochemical CO_(2)conversion is one of the most promising technologies to achieve carbon neutrality.However,it still suffers from some nonnegligible challenges on low production rate and unsatisfied current densities for potential large-scale applications.Herein,we prepare ultrasmall Bi nanoparticles uniformly encapsulated in the carbon nanofibers through electrospinning techniques,which is denoted as Bi/CNFs-900.Gratifyingly,this Bi/CNFs-900 catalyst demonstrates excellent performance and stability on CO_(2)electro-reduction in a broad potential window.Specifically,it can produce formate with a Faradaic efficiency over 90%and a high partial current density of-235.3mA cm^(-2)at-1.23 V vs.RHE in a flow-cell.Furthermore,the confinement effect of carbon nanofibers largely restricts the severe aggregation of bismuth nanoparticles during synthesis as well as electrolysis procedure,which greatly increases the accessible active sites and decreases the actual mass fraction of bismuth composition.Consequently,Bi/CNFs-900 not only achieves ultrahigh mass activity of-1.6 A mg_(Bi)^(-1),but also possesses an unprecedented formate production rate of 4403.3μmol h^(-1)cm^(-2).DFT calculations and in situ Raman spectroscopy further uncover the possible reaction mechanism for CO_(2)reduction toward formate.These results could provide an economical and industrial-viable strategy for the preparation of electrocatalysts in CO_(2)reduction.
作者
孔艳
蒋兴星
李轩
孙建桔
胡琪
柴晓燕
杨恒攀
何传新
Yan Kong;Xingxing Jiang;Xuan Li;Jianju Sun;Qi Hu;Xiaoyan Chai;Hengpan Yang;Chuanxin He(Department of Chemical Physics,University of Science and Technology of China,Hefei 230026,Anhui,China;College of Chemistry and Environmental Engineering,Shenzhen University,Shenzhen 518060,Guangdong,China)
基金
国家自然科学基金(U21A20312,22172099,51902209)
广东省自然科学基金(2020A1515010840)
深圳市科技计划资助(RCBS20200714114819161,JCYJ20190808111801674,JCYJ20200109105803806,SGDX20201103095802006).
关键词
二氧化碳电还原
铋纳米颗粒
碳纳米纤维
甲酸
质量活性
CO_(2)electro-reduction
Bismuth nanoparticle
Carbon nanofiber
Formate
Mass activity
