摘要
金属-空气电池因其高效率和便携性受到广泛关注.然而,氧还原反应(ORR)的高能垒和缓慢的动力学导致其输出功率低.尽管贵金属铂基材料具有较高的ORR活性,但其在工业上的大规模应用受到高成本的制约.因此,迫切需要以储量丰富的非贵金属为原料,开发具有低成本、高性能和耐用性的催化剂.近年来,单原子过渡金属与氮共掺杂碳材料(M-N-C)成为替代贵金属催化剂的理想材料.理论模拟和实验结果均表明,单原子Fe/Co-N-C催化剂具有良好的ORR活性,其中FeN_(4)和CoN_(4)构型被认为是主要活性位点.此外,含有相邻金属位点的双金属单原子催化剂具有加速ORR动力学的巨大潜力.通过对ORR中间体的桥式-顺式吸附,双金属位点可以促进O-O键的裂解,从而提高催化活性.除固有活性外,双金属位点可减少ORR过程中含氧中间体对M-N键的攻击,提高M-N-C对ORR的耐久性和工业应用潜力.因此,近年来,研究者开始探索双金属单原子催化剂的合成和电催化性能,发现Fe-Co, Fe-Mn, Fe-Cu, Co-Zn和Co-Pt双位点可以有效催化ORR.为进一步提高ORR活性,需要合理调节双原子结构,并引入更多的双金属位点.本文在氮掺杂石墨烯纳米片上构建了一种含FeN_(3)-CoN_(3)位点的新型双原子催化剂(CoFe-NG),该催化剂具有较好的ORR催化活性,半波电位为0.917 V, Tafel斜率为46 mV dec^(-1),远远优于单原子Fe-NG、单原子Co-NG和Pt/C催化剂.Koutecky-Levich曲线和H_(2)O_(2)产率揭示了CoFe-NG具有高效的四电子ORR过程,不仅表现出高电流密度,而且对氧还原为OH-(而不是过氧化氢)更具选择性.计时安培测试结果表明, CoFe-NG对甲醇和一氧化碳中毒具有较高的耐受性.KSCN中毒实验结果表明, SCN^(-)离子与Fe和Co位点发生强配位作用并使活性位点中毒.以CoFe-NG为空气电极组装的锌-空气电池,开路电压为1.47 V,峰值功率密度高达230 mW cm^(-2),具有良好的充放电循环稳定性,可以为一个小灯泡供电,并且在5 mA cm^(-2)条件下持续充放电250 h,输出电压几乎不变.理论计算表明,掺氮石墨烯上的FeN_(3)-CoN_(3)位点比FeN_(4)和CoN_(4)位点具有更低的ORR能垒, FeN_(3)-CoN_(3)位点上的速控步是^(*)OH中间体向H_(2)O的转化,与单位点FeN_(4)和CoN_(4)不同.综上,本文为可控合成高性能双金属单原子催化剂及进一步深入分析其电催化氧还原反应机理提供参考.
Controlled synthesis of dual-atom catalysts(DACs) for heterogeneous catalytic reactions is vital but still demanding. Herein, we construct a novel dual-atom catalyst containing FeN_(3)-CoN_(3) sites on N-doped graphene nanosheets(CoFe-NG), which exhibits remarkable catalytic performance with a half-wave potential of 0.952 V for oxygen reduction reaction(ORR) and shows higher endurance to methanol/carbon monoxide poisoning and better durability than commercial Pt/C. The assembled Zn-air battery with CoFe-NG as the air electrode delivers a peak power density of 230 mW cm^(-2) and exhibits negligible change in output voltage at 5 mA cm^(-2) for 250 h. Theoretical calculations reveal that FeN_(3)-CoN_(3) sites on N-doped graphene exhibit lower ORR barrier than FeN_(4) and CoN_(4) sites, and the rate-limiting step on the former is the transformation of ^(*)OH intermediate to H_(2)O, different from the transformation of ^(*)O to ^(*)OH on the FeN_(4) site and the transformation of O_(2) to ^(*)OOH on the CoN_(4) site.
作者
唐甜蜜
王寅
韩憬怡
张巧巧
白雪
牛效迪
王振旅
管景奇
Tianmi Tang;Yin Wang;Jingyi Han;Qiaoqiao Zhang;Xue Bai;Xiaodi Niu;Zhenlu Wang;Jingqi Guan(Institute of Physical Chemistry,College of Chemistry,Jilin University,Changchun 130021,Jilin,China;College of Food Science and Engineering,Jilin University,Changchun 130062,Jilin,China;Inner Mongolia Key Laboratory of Carbon Nanomaterials,Nano Innovation Institute(NII),College of Chemistry and Materials Science,Inner Mongolia Minzu University,Tongliao 028000,Inner Mongolia,China)
基金
国家自然科学基金(22075099)
吉林省自然科学基金(20220101051JC)
吉林省教育厅项目(JJKH20220967KJ,JJKH20220968CY).
