Active Sites Implanted Carbon Cages in Core ... - ACS Publications

Active Sites Implanted Carbon Cages in Core− Shell Architecture: Highly Active and Durable Electrocatalyst for Hydrogen Evolution Reaction Huabin Zhang,†,‡ Zuju Ma,§ Jingjing Duan,⊥ Huimin Liu,‡ Guigao Liu,‡ Tao Wang,‡ Kun Chang,‡ Mu Li,‡ Li Shi,‡ Xianguang Meng,‡ Kechen Wu,§ and Jinhua Ye*,†,‡ †

TU-NIMS Joint Research Center, and Key Lab of Advanced Ceramics and Machining Techonology of Ministry of Education, School of Materials Science and Engineering, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, PR China ‡ Environmental Remediation Materials Unit, and International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan § Fujian Institute of Research on the Structure of Matter, The Chinese Academy of Sciences, Fuzhou 350002, PR China ⊥ School of Chemical Engineering, The University of Adelaide, Adelaide, South Australia 5005, Australia S Supporting Information *

ABSTRACT: Low efficiency and poor stability are two major challenges we encounter in the exploration of non-noble metal electrocatalysts for the hydrogen evolution reaction (HER) in both acidic and alkaline environment. Herein, the hybrid of cobalt encapsulated by N, B codoped ultrathin carbon cages (Co@BCN) is first introduced as a highly active and durable nonprecious metal electrocatalysts for HER, which is constructed by a bottom-up approach using metal organic frameworks (MOFs) as precursor and self-sacrificing template. The optimized catalyst exhibited remarkable electrocatalytic performance for hydrogen production from both both acidic and alkaline media. Stability investigation reveals the overcoating of carbon cages can effectively avoid the corrosion and oxidation of the catalyst under extreme acidic and alkaline environment. Electrochemical active surface area (EASA) evaluation and density functional theory (DFT) calculations revealed that the synergetic effect between the encapsulated cobalt nanoparticle and the N, B codoped carbon shell played the fundamental role in the superior HER catalytic performance. KEYWORDS: core/shell nanoparticles, catalysis, N/B codoping, active surface area, hydrogen evolution reaction

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one ideal channel to enable the hydrogen economy. Toward this end, great advances for replacement of Pt-based catalysts have been achieved owing to the development of series of electrocatalysts with good catalytic performance and low cost,3−5 such as transition-metal sulfides,6−10 selenide,11,12 carbides,13−18 phosphides,19−23 oxide,24,25 and nitrides.26,27 However, most of the catalysts currently being developed rely on metal−H bond interaction for the HER, which generally suffers from corrosion and passivation under the extreme environment of strong acid and alkali. Metal nanoparticles

ncreasing global concerns over energy crisis and environmental issues have triggered a great deal of attention in the development of new technologies for sustainable and clean energy. Hydrogen as abundant, secure, and renewable alternative energy carrier can meet the growing global energy requirement, and the wide application of hygrogen only can be realized through its efficient, low-cost, and environmentalfriendly production.1,2 Electrochemical reduction of water to molecular hydrogen is a highly attractive approach to satisfy these requirements. Among the many hydrogen evolution reaction (HER) electrocatalysts, platinum (Pt) gives the best performance, but its application is greatly limited by the scarcity and high cost. Searching and developing high-performance, low cost alternatives to the noble metal electrocatalysts serves as © 2015 American Chemical Society

Received: September 11, 2015 Accepted: December 3, 2015 Published: December 9, 2015 684

DOI: 10.1021/acsnano.5b05728 ACS Nano 2016, 10, 684−694

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ACS Nano encapsulated by carbon layers (M@C) are promising nanostructures with high chemical durability, as the encapsulating carbon layers can protect the inner nanoparticles from electrolyte, thus avoid the corrosion and oxidization from external environment as well as prevent the agglomeration with neighboring nanoparticles. Few carbon-layers encapsulated metal nanoparticles have been confirmed to be able to catalyze the oxygen reduction reaction (ORR) and HER.28−30 However, in these structures, the outermost carbon layer is less modified by the inner core and failed to provide enough active sites, resulting in dissatisfying catalytic activity.31−33 On the basis of current situation, it is essiential for us to modify the external carbon cages aiming at providing enough active sites in the HER process. It is well documented that electronic structure of graphene can be effiectivly modified by chemical replacement of some carbon atoms with heteroatoms, such as nitrogen (N), boron (B), sulfur (S), and phosphorus (P). In particular, the codoping of two elements in reverse electronegativity to that of carbon, e.g., B and N, could activate adjacent carbon atoms by the so-called synergistic coupling effect between two heteroatoms and, consequently, greatly enlarge catalytic active surface area.34−36 And thus, it is anticipated that the carbon cages of M@C can be tailored by the codoping of B and N, which will produce additional active sites to enhance the HER performance. However, to our knowledge, modification of ultrathin carbon shell (carbon layers