Controlled growth of a graphdiyne/cobalt hydroxide heterointerface for efficient chlorine production

Abstract

The chlor-alkali process plays a key and irreplaceable role in the chemical industry because of its use in various industrial processes. However, the low selectivity and efficiency of the reported chlorine evolution reaction (CER) electrocatalysts obviously hinder its practical use. We report a simple method for the controlled growth of high-performance CER electrocatalysts by first growing cobalt hydroxide on the surface of carbon cloth, followed by the in-situ growth of graphdiyne (GDY/Co(OH)2). As expected, the as-synthesized catalyst has a small overpotential of only 83 mV at 10 mA cm−2, a maximum Faradaic Efficiency (FE) of 91.54%, and a high chlorine yield of 157.11 mg h−1 cm−2 in acidic simulated seawater. Experimental results demonstrate that the in-situ growth of GDY on the Co(OH)2 surface leads to the formation of heterointerfaces with strong electron transfer between GDY and Co atoms, resulting in a higher conductivity, larger active specific surface area and more active sites, thereby improving the overall electrocatalytic selectivity and efficiency.

1. Introduction

Chlorine plays a crucial role in modern chemical industries including water treatment, disinfection, advanced technology and the products that contribute to public health and safety[1–4]. During the past decades, dimensionally stable anodes (DSAs) based on RuO2 and IrO2 have been established as electrocatalysts for chlor-alkali process, but limited by their intrinsic poor activity and low selectivity[5,6]. Besides, the RuO2 and IrO2 species in DSA are supposed to be active for oxygen evolution reaction (OER), which is the key competitive reaction to chlorine evolution reaction (CER)[7], unavoidably reducing the overall electrocatalytic performances regarding the CER[8–11]. The design and synthesis of Ru/Ir-free catalysts with high selectivity and efficiency towards chlorine production from seawater are still in great demand.

Graphdiyne (GDY) has attracted increasing attention in various catalysis and energy-related applications because of its unique structures and properties such as the alkyne-rich structures, high intrinsic activity, the abundance of sp-hybridized pores, high conductivity, and strong integer charge transfer between GDY and metal atoms[12–19]. Especially, the property of GDY that it can be grown on the surface of any substrate provides significant advantages for the controlled growth of heterointerface structures with excellent selectivity, activity and stability[20–23]. Extensive studies have demonstrated that GDY is an ideal platform for constructing new materials with excellent selectivity, activity and stability[24–27]. Various GDY-based materials were successfully synthesized and used as highly efficient electrocatalysts for various chemical conversion reactions including the oxygen evolution reactions[21,28], hydrogen evolution reactions[29–32], N2/CO2/O2 reduction reactions[33–38] and methanol oxidation reactions[39–41]. However, the design of GDY-based electrocatalysts for CER has not been reported. Transition metal-based materials are considered efficient catalysts to replace noble metals due to their affordability and convenient industrial production processes[42–49]. On another hand, recent studies show that cobalt atoms possess stronger Cl− binding energy for pre-adsorption of Cl−, which might benefit the following activation of Cl− to Cl2[50,51].