Non-noble Metal Based ODC Cathodes for Chlorine Evolution Processes

INV-13048

 

Use of “depolarizers” in electrolytic reactions helps lower input electrical energy in electrochemical processes. For example, in batteries depolarizers help prevent buildup of hydrogen gas bubbles thereby preventing the voltage, and thereby current, from being reduced. Among the known depolarizers, including sulfur dioxide which is used for lowering energy use in production of hydrogen, oxygen consuming cathodes have gained in importance due to the high onset potential of the oxygen reduction reaction (ORR). Oxygen depolarized cathodes are used in the electrolytic production of chlorine from brine solution, and in its recovery from hydrochloric acid, a byproduct of various chemical processes. Chlorine is a key component for production of many polymers, notably polyvinyl chloride, polyurethanes, and polycarbonates. The existing chlorine generation techniques involve the use of expensive and precious noble metals such as platinum and rhodium. 

This invention discloses a novel technique comprising the use of non-noble metal- based oxygen depolarized cathodes for hydrochloric acid (HCL) recovery and chlorine generation.

 

This invention describes a new generation of non-precious metal based electrocatalysts for oxygen-depolarized cathodes (ODC), used in HCl recovery and chlorine generation process. In this invention, highly anion-resistant electrocatalysts suitable for catalyzing an oxygen reduction reaction (ORR) and methods of synthesizing the same are provided. The catalysts contain a transition metal, a heteroatom, and carbon. Preferred catalysts include N as the heteroatom and Fe as the transition metal, with active sites having Fe—N4 stoichiometry (FexNyCz) as part of a metal-organic framework (MOF) or sequestered within a MOF. Electrocatalysts further including Fe nanoparticles (FeNPs) are also provided. The catalysts described herein are applicable in the preparation of oxygen decoupled cathodes (ODC) for chlorine evolution processes such as in chlor-alkali cells or HCl electrolyzers. The catalysts are also useful in preparing ODC for use in fuel cells, including phosphoric acid fuel cells.

 

- Safe and cost-effective

- Reduced CO2 emission

- Highly durable and dissolution resistant cathodes 

- Allows for specifically designed active sites, which are immune to anion poisons

- Allows for the formation of robust polymer networks with high selectivity for oxygen reduction (103 times higher turnover frequency)

- Higher resistance to the corrosive environment 

 

- Chlorine gas recycling at many chemical plants, including polyvinylchloride (PVC), polyurethane (PU) and polycarbonate (PC)

- HCl recovery and recycling in chemical industry where Cl2 is an input. Most chemical synthesis processes include such sub-units

- It is also used in fuel cells, industrial gases, chlorine production

 

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