Tuning the Activity of Carbon for Electrocatalytic Hydrogen Evolution via an Iridium-Cobalt Alloy Core Encapsulated in Nitrogen-Doped Carbon Cages
Tuning the Activity of Carbon for Electrocatalytic Hydrogen Evolution via an Iridium-Cobalt Alloy Core Encapsulated in Nitrogen-Doped Carbon Cages
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通过封装在掺氮碳笼中的铱钴合金核心调节碳的电催化析氢活性
DOI：
10.1002/adma.201705324
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发表时间：
2018-03-01
影响因子：
29.4
通讯作者：
Chen, Qianwang
中科院分区：
文献类型：
--
作者：
Jiang, Peng;Chen, Jitang;Chen, Qianwang
石墨烯是一种由单层sp(2)杂化碳组成的2D材料，作为电催化剂表现出惰性活性，而杂原子(如N)的引入可以调节其电子性质。由于N原子和C原子之间的电负性不同，在N掺杂石墨烯纳米片中，电子会从C原子转移到N原子，使与N原子相邻的惰性C原子变成活性中心。尽管已经取得了一些进展，但其在酸性介质中的本征活性仍远未达到铂/碳的水平。本文采用一种简单的退火法对Ir掺杂的金属-有机骨架进行了研究，合成了包覆在N掺杂石墨烯层中的IrCo纳米合金。在0.5m硫酸溶液中，当电流密度为10 mA cm(-2)时，该高活性电催化剂的Tafel斜率为23 mV dec(-1)，过电位仅为24 mV，Ir负载量(1.56%)显著降低。如此优越的性能甚至超过了贵金属催化剂铂。表面结构和计算研究表明，这种优越的行为源于电子从合金核转移到石墨烯层而导致HER的G(H*)降低，这有利于增强CH键。
Graphene, a 2D material consisting of a single layer of sp(2)-hybridized carbon, exhibits inert activity as an electrocatalyst, while the incorporation of heteroatoms (such as N) into the framework can tune its electronic properties. Because of the different electronegativity between N and C atoms, electrons will transfer from C to N in N-doped graphene nanosheets, changing inert C atoms adjacent to the N-dopants into active sites. Notwithstanding the achieved progress, its intrinsic activity in acidic media is still far from Pt/C. Here, a facile annealing strategy is adopted for Ir-doped metal-organic frameworks to synthesize IrCo nanoalloys encapsulated in N-doped graphene layers. The highly active electrocatalyst, with remarkably reduced Ir loading (1.56 wt%), achieves an ultralow Tafel slope of 23 mV dec(-1) and an overpotential of only 24 mV at a current density of 10 mA cm(-2) in 0.5 m sulfuric acid solution. Such superior performance is even superior to the noble-metal catalyst Pt. Surface structural and computational studies reveal that the superior behavior originates from the decreased G(H*) for HER induced by the electrons transferred from the alloy core to the graphene layers, which is beneficial for enhancing CH binding.