Bimetallic Metal-Organic Framework Derived Metal-Carbon Hybrid for Efficient Reversible Oxygen Electrocatalysis.

Yu Zhou,Shenlong Zhao,Zonghua Wang,Yan Zhang,Chunhui Tan,Kuang-Hsu Wu,Xianzhen Xu,Ziyi Guo

doi:10.3389/fchem.2019.00747

Abstract

Development of cost-effective electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is key to enabling advanced electrochemical energy conversion technologies. Here, a novel nitrogen-doped metal-carbon hybrid (NiCo/CN) with a unique 3D hierarchical structure, consisting of uniformly distributed bimetallic nanoparticles encapsulated by partially graphitized N-doped carbon shells, is fabricated by a one-step pyrolysis of a nanoscale metal-organic framework as precursor, which exhibits excellent activity for both ORR and OER. The surface chemical changes on the carbon hybrid probed by X-ray photoelectron spectroscopy (XPS) reveal the presence of favorable electronic interaction at the metal-nitrogen-carbon interface. Remarkably, the NiCo/CN catalyst prepared at high temperature (800°C) manifests a comparable performance to a commercial Pt/C catalyst for the ORR, but also superior stability, path selectivity and methanol tolerance. On the other hand, the Eonset (1.48 V vs. reversible hydrogen electrode) and of NiCo/CN-800 for OER is very close to the state-of-the-art noble catalyst RuO2 (Eonset = 1.46 and ) along with superior stability over 20 h of operation. The excellent catalytic property is attributable to the unique nanostructure, high porosity and the constructive synergistic effects of the elements M, N, and C.

Highlights

Reversible oxygen reactions, including the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), are becoming increasingly important for many renewable conversion technologies and other important industrial processes (Pei et al, 2017; Gong et al, 2018; Zheng et al, 2019)
The results show that when the doping ratio is around 40% and the pyrolysis temperature is about 800◦C, the obtained catalyst exhibits the highest electrocatalytic activities among all the samples
After injecting 1 M methanol at 300th s, the voltammetric current of the NiCo/CN-800 catalyst was nearly without change, whereas an observed current attenuation can be seen for commercial Pt/C, demonstrating the excellent selectivity of the as-prepared NiCo/CN-800 catalyst. These results indicate that the NiCo/CN-800 catalyst maintains high stability in an alkaline solution and has high selectivity and outstanding methanol tolerance for ORR

Summary

INTRODUCTION

Reversible oxygen reactions, including the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), are becoming increasingly important for many renewable conversion technologies and other important industrial processes (Pei et al, 2017; Gong et al, 2018; Zheng et al, 2019). Compared with NiCo/ZIF-67, the ORR activity of NiCo/CN-800 significantly enhanced, indicating that the high-temperature carbonization is beneficial to enhancing the oxygen reduction performance. The excellent stability should be mainly attributed to the porous structure of the as-prepared NiCo/CN-800

CONCLUSIONS

Findings

DATA AVAILABILITY STATEMENT