Atomically dispersed Pt\u2013N4 sites as efficient and selective electrocatalysts for the chlorine evolution reaction

Taejung Lim,Sang Kyu Kwak,Sang Hoon Joo,Jaehyun Park,Sung O Park,Yong-Tae Kim,Hu Young Jeong,Jae Hyung Kim,Gwan Yeong Jung,Seok Ju Kang

doi:10.1038/s41467-019-14272-1

Abstract

Chlorine evolution reaction (CER) is a critical anode reaction in chlor-alkali electrolysis. Although precious metal-based mixed metal oxides (MMOs) have been widely used as CER catalysts, they suffer from the concomitant generation of oxygen during the CER. Herein, we demonstrate that atomically dispersed Pt−N4 sites doped on a carbon nanotube (Pt1/CNT) can catalyse the CER with excellent activity and selectivity. The Pt1/CNT catalyst shows superior CER activity to a Pt nanoparticle-based catalyst and a commercial Ru/Ir-based MMO catalyst. Notably, Pt1/CNT exhibits near 100% CER selectivity even in acidic media, with low Cl− concentrations (0.1 M), as well as in neutral media, whereas the MMO catalyst shows substantially lower CER selectivity. In situ electrochemical X-ray absorption spectroscopy reveals the direct adsorption of Cl− on Pt−N4 sites during the CER. Density functional theory calculations suggest the PtN4C12 site as the most plausible active site structure for the CER.

Highlights

Chlorine evolution reaction (CER) is a critical anode reaction in chlor-alkali electrolysis
Among the prepared Pt1/CNT_X samples, the best CER activity was obtained with the sample treated at 700 °C, which is hereafter denoted as Pt1/CNT
We demonstrated that Pt1/CNT with atomically dispersed Pt−N4 sites could catalyse CER with high activity and selectivity

Summary

Introduction

Chlorine evolution reaction (CER) is a critical anode reaction in chlor-alkali electrolysis. The current Cl2 production is prevalently dependent on the chlor-alkali process[4,5], for which the electrochemical chlorine evolution reaction (CER) plays a pivotal role as the anodic reaction[5,6,7,8]. Computational and experimental works revealed that MMO catalysts are highly active for the OER, exhibiting a scaling relationship between the CER and OER13,17–20. This relationship suggests that two reactions are catalysed on a similar active site of the MMOs or form a common surface intermediate species[20,21,22,23,24]. To the best of our knowledge, the atomically dispersed catalysts have never been exploited as an electrocatalyst for the CER, and only homogeneous electrocatalysts for generating Cl2 (refs. 41,42) or ClO2 (refs. 43,44) have sporadically been reported

Methods

Results

Conclusion