Recovery of High Purity Chlorine by Cu‐Doped Fe₂O₃ in Nitrogen Containing Carbon Matrix: A Bifunctional Electrocatalyst for HCl Electrolysis

Abstract

An environmentally benign approach towards synthesis of a non‐noble metal and/or metal oxide doped incorporated in nitrogen containing carbon matrix (Cu−Fe2O3/NC) is premeditated in this study. In‐situ incorporation of Cu, Fe2O3 as well as nitrogen into the carbon matrix using a single gel precursor simplified the synthetic route and divulged bifunctional activity assisting chlorine evolution at anode and oxygen reduction reaction at cathodic counterpart during HCl electrolysis. As a result of synergy between Cu and Fe2O3 in N‐ doped carbon matrix, enhanced activity and stability is stimulated. Catalyst optimization was executed by varying the weight percentage of metal reactants added during precursor synthesis (2, 5 and 10 wt. %), which rendered different composition of Cu, Fe2O3 and N in the composite with flake‐like morphology at same thermal treatment conditions. Electrochemical studies were performed in 0.4 M HCl analogous to industrial waste HCl, to investigate the bifunctional activity of catalyst where Cu−Fe2O3 (5 %)/NC came out to be the most active and exhibited long term stability for 24 hours at onset potential of chlorine evolution. It offered a higher current density of 92.1 mA cm−2 at 1.7 V vs. RHE during chlorine evolution and comparable activity to that of benchmark noble metal based catalyst along with more positive onset potential and high diffusion limiting current density of 0.78 V vs. RHE and 6 mA cm−2 during oxygen reduction respectively.

Recent advances in energy-efficient chlorine production via HCl electrolysis

“…25 Transition metal-based catalyst Apart from carbonaceous materials, the doping of certain transition metal-based catalyst have been explored for ODC. 20,51,95,98 For example, it was studied that O 2 atmosphere and a solid electrolyte interface on Fe impacts the ODC performance (Fig. 4j and k).…”

“…However, utilizing different catalysts for anodic and cathodic reaction will increase the system's operational cost and complexity. 59,95,101 Various approaches have been put forward towards the development of CER-ODC bifunctional electrocatalyst (as summerised in Table 4). 105 In that context, Singh et al 22 utilized a composite of ZnPOM and OCNT as bifunctional catalysts for CER and ODC.…”

“…However, utilizing different catalysts for anodic and cathodic reaction will increase the system's operational cost and complexity. 59,95,101…”

“…Therefore, this catalyst is a sustainable substitute for noble metal-based catalyst for HCl electrolysis. 95 In situ incorporation of cobalt metal with nitrogen was utilized with carbon matrix (Fig. 5d), which imparted the bifunctional activity in HCl electrolysis.…”

“…This process is energy intensive and accounts for a large energy (∼1500 kW h per metric ton of Cl 2 production) as well as power consumption. 20,21 Holds a high overall cell potential of −1.36 V. [22][23][24] Imposes major safety concerns due to the generation of H 2 at cathode and chloride/chlorine crossover from the anode to the cathode during unwanted industrial shutdowns and may result in potential explosion. 20 These bottlenecks can be resolved by replacing the cathodic hydrogen evolution reaction with oxygen reduction reaction (ORR).…”