Elsevier

Materials Letters

Volume 264, 1 April 2020, 127308
Materials Letters

Pd supported on Co@CN derived from ZIF-67 as catalyst for hydrogen generation from formic acid

https://doi.org/10.1016/j.matlet.2020.127308Get rights and content

Highlight

  • Porous carbon derived from ZIF-67 acted as support for Pd nanoparticles.

  • The Pd/Co@CN acquired high activity for dehydrogenation of formic acid.

  • Co modulated electronic state and structure of Pd.

  • N species promoted the formation of well-dispersed nanoparticles.

Abstract

Hydrogen generation from formic acid (FA) is a promising route in hydrogen energy supply, and catalyst is considered to be the key to this process. Herein, Pd nanoparticles assembled on porous carbon (Co@CN) which derived from ZIF-67, wherein Co species inherited from precursors plays as assistant to adjust the electronic and structure of Pd. In addition, the N atom on the porous carbon skeleton also modified the electronic state of Pd and promoted the anchoring of Pd nanoparticles. The as-synthesized catalyst (Pd/Co@CN) acquired high activity (TOF of 1403 h−1) and stability toward decomposition of FA at 30 °C.

Introduction

Hydrogen has attracted wide attention as a propitious energy in a number of fields. Formic acid (FA) is considered as a promising chemical hydrogen storage media due to the unique characteristics of nontoxicity, excellent stability, high hydrogen content (ca. 4.4 wt%). Numerous researches [1], [2] have been devoted to exploring catalysts for hydrogen generation form FA. Pd catalysts are used in decomposition of FA. Incorporation of non-precious metal into the Pd catalysts may not only tailor electronic properties and geometric structure of Pd nanoparticles (NPs) to enhance the catalytic activity and selectivity, but also reduce the consumption of the noble metals [3], [4]. Besides, doping N-containing functional groups into support materials modify Pd electron state [5] and facilitate the anchoring of Pd NPs to increase its dispersity [6].

Zeolitic imidazolate frameworks (ZIFs) composed of 2-methyl imidazolate (2-mIM) ligands coordinated with transition metal cations that results in a sodalite (SOD) topology. ZIFs have emerged as promising precursors for the production of transition-metal and N-doped porous carbon composite materials by pyrolysis [7]. Herein, for the first time, we report Pd NPs immobilized in porous carbon derived from ZIF-67 as efficient catalysts, which exhibit good activity for FA decomposition to hydrogen.

Section snippets

Experiment

ZIF-67 was synthesized at room temperature and carbonized at 900 °C in Ar flow for using as catalyst support (denoted as Co@CN, wherein CN means N-rich porous carbon). Co@CN was sonicated in deionized water and then the solution of H2PdCl4 were added in it by stirring at room temperature. NaBH4 was added for reduction after adjusting the pH value. The catalyst was obtained after centrifugal, washing and drying (denoted as Pd/Co@CN). For comparison, Pd/CN (treating Co@CN with HF to remove Co)

Results and discussion

The XRD pattern of the catalysts indexed to parental ZIFs (Fig. S2) disappear by the observation of new peaks (Fig. 1a), indicating the destruction of the initial structure. The peak was observed at 2θ = 26.0°, which can be assigned to the (0 0 2) planes of graphitic carbon (JCPDS: 41–1487). This was due to Co acted as a catalyst for growth of highly graphitic frameworks [8]. For Co@CN, the diffraction peaks at 2θ = 44.0° (JCPDS: 15–0806) derived from the (1 1 1) diffraction of Co. Compared

Conclusions

In summary, Pd NPs assembled on porous carbon which derived from ZIF-67, which provides a method to prepare well-dispersed Pd catalyst for the hydrogen generation from FA without undesired CO contamination. The Co and N species inherited from ZIF-67 improved the catalytic activity of Pd by regulating its electronic state and structure and promoting its dispersion. The excellent performance of catalyst (TOF of 1403 h−1) was highlighting the feasibility of renewable FA as a convenient in situ

CRediT authorship contribution statement

Mengqin Yao: Conceptualization, Methodology, Data curation, Writing - original draft. Yuling Ye: Visualization, Investigation. Honglin Chen: Writing - review & editing. Xiaoming Zhang: Supervision.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

This work was supported by the National Key R&D Program of China [grant number 2018YFB0604902].

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