Elsevier

Catalysis Communications

Volume 78, 10 March 2016, Pages 1-6
Catalysis Communications

Short communication
Highly efficient supporting material derived from used cigarette filter for oxygen reduction reaction

https://doi.org/10.1016/j.catcom.2016.01.030Get rights and content

Highlights

  • N-doped carbon (NCF) was synthesized via recycling used-cigarette filters.

  • NCF exhibited ORR kinetics without loading Pt.

  • N-dopant acted as nucleation sites for Pt nanoparticles, leading to high dispersion.

  • Pt/NCF showed higher electrocatalytic behavior than that for commercial Pt/C.

Abstract

Bimodal porous nitrogen (N) doped carbon supported Pt composite was prepared as a catalyst for oxygen reduction reaction (ORR). The N-doped carbon (NCF) support was obtained via one-pot pyrolysis of the used cigarette filters. Physical characterizations and electrochemical tests proved that the presence of N dopant on the surface of the NCF not only provided highly dispersive active sites for the growth of the Pt nanoparticles but also the active centers for ORR itself. It was demonstrated that these combinative effects contributed on higher ORR activity and durability than those for the commercial carbon (Vulcan XC) supported Pt composites.

Introduction

Developing proper catalysts for the oxygen reduction reaction (ORR) is the current issue for the industrial development of fuel cells [1]. During the past years, Pt has been used as the commercial electrocatalyst for the ORR due to its high activity [2]. Owing to the high cost and limited storage of Pt, however, decreasing the amount of usage with enhancing the catalytic activity of Pt catalyst has been come into a compulsory aim [3].

One of the available strategies to meet the demand is the increase of the active surface area of Pt by adopting appropriate supporting material (e.g., carbon material), which enables the high dispersion of Pt nanoparticles [4], [5]. It has been reported that the catalytic performances such as onset potential, current density, and durability are susceptible to the type of catalytic supporting material [6]. The requirements for carbon material as a support are high surface area, good conductivity, and proper pore structure, which provide the uniformly distributed anchoring sites for Pt catalysts and facilitate the smooth electrolyte flux for effective catalytic reaction without hampering electron transfer [7].

Nitrogen (N)-doped carbon with bimodal structure, which consists of micropores and mesopores, is a proper candidate material for supporting the Pt nanoparticles [8]. Typically, the bimodal pore system can induce the high surface area, which confers an increased distribution of C–N catalytic center and provide the easier accessibility to active sites for reactants [9]. More importantly, it has been reported that the presence of N dopants on the carbon surface not only can donate excess electrons for the fine nucleation of Pt nanoparticles but also limit the mobility of Pt nanoparticles by metal–N interaction, which prevent them from agglomeration [10]. Moreover, the substituted N atoms are known to have the catalytic activity toward ORR [11]. Thus, it could be another contribution factor for exhibiting high catalytic performance. These physicochemical properties are beneficial to design an effective Pt-based electrocatalyst possessing highly dispersive Pt nanoparticles by inducing N species on the entire surface of the carbon supporting material.

There have been several methods for the preparation of the N-doped carbon supporting material such as carbonization of organic material that readily containing N species, heat treatment of organics and/or carbon with N-containing gases, and utilizing N-containing chemicals with carbon sources together before the carbonization [12], [13], [14], [15]. Among these, carbonization of organic material with ammonia (NH3) gas enables N doping within the carbon matrix and simultaneously allows formation of porous structure on the whole surface by a pyrolysis, which can be a powerful approach for achieving the desirable physicochemical properties for the carbon based electrocatalyst toward the ORR at one-step procedure [16].

In this study, we report on a simple and environmentally benign route to the scalable production of well dispersed Pt on hierarchical N-doped porous carbon (Pt/NCF) via one-pot carbonization of used cigarette filters and direct reduction of Pt. This synthetic strategy possesses the following desirable advantages: (1) recycling used cigarette filters as a carbon source for use in a Pt support, (2) developing the bimodal pore structure, which can provide large surface area and fast oxygen insertion and desertion and (3) simultaneous introduction of the N functional groups into this supporting material, which can play a key role in the formation of homogeneous nucleation sites for highly dispersed Pt nanoparticles and catalytic active sites toward the ORR. To the best of our knowledge, a study of the feasibility of preparing bimodal porous carbon material synthesized from used cigarette filters and its usage as a supporting material of Pt nanoparticles for ORR have not been reported yet.

Section snippets

Preparation of catalysts

As a feasible approach, we chose the world-widely consumed cigarette brand (Marlboro Light Gold produced by Philip Morris Int.) and popular brands (The One Orange and Bohem Cigar Mojito produced by Korea Tobacco & Ginseng Corp.) in our country, Republic of Korea together, as a model case. These industrial cigarette filters are largely composed of cellulose acetate (> 95%), which reveals that no significant differences toward the origin of carbon source between each brand is chemically negligible

Results and discussion

Fig. 1(a) shows the features of used cigarette filters and the as-synthesized Pt/NCF20 powder. Fig. 1(b) shows the SEM image of the used cigarette filter fiber with the cross-sectional shape of alphabet “Y”. It is widely known that the industrially produced cigarette filters are composed largely of cellulose acetate. Overall morphology and size of NCF are irregular because the bulk carbon particle is physically grinded before the Pt deposition as shown in Fig. S1. The morphologies of NCF,

Conclusions

This work reports a green approach for the fabrication of Pt based electrocatalyst (Pt/NCF20) by recycling the used cigarette filters. Well-dispersive N dopants on the surface of the NCF provided nucleation sites for Pt nanoparticles, resulting in higher Pt dispersion on the surface of the NCF than that of the commercially used carbon support (Vulcan XC). Bimodal pore size distribution and N dopants also contributed on the enhanced activity toward the ORR, resulting in the improved

Acknowledgements

This research was supported by the Global Frontier R&D Program on Center for Multiscale Energy System funded by the National Research Foundation under the Ministry of Science, ICT & Future, Korea (NRF-2011-0031571) and the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (No. 2013R1A2A2A01067164).

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    Gil-Pyo Kim and Minzae Lee contributed equally to this work.

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