Electrochemical Hydrogen Sulfide Decomposition Using Proton Conducting Ceramic for Pure Hydrogen Production

Abstract

Hydrogen sulfide (H2S) is a substance that occurs during the process of processing sulfur, which is abundant in fossil fuels such as oil and natural gas, into high-quality fuel. Due to its high toxicity, it is classified as harmful industrial waste and removal in the process of discharging is essential. Until now, refiners have used the Claus process and the Wet Sulfuric Acid (WSA) process, which reacts hydrogen sulfide with oxygen to release it in the form of water or sulfuric acid. These processes require a huge amount of heat energy and only aim to remove hydrogen sulfide, so they emit hydrogen atoms contained in hydrogen sulfide in the form of water and sulfuric acid. Because hydrogen is an eco-friendly energy source that has recently been in the spotlight, hydrogen sulfide can be a valuable resource if hydrogen can be extracted from hydrogen sulfide. In this study, an electrochemical process that decomposes hydrogen sulfide and obtains hydrogen from hydrogen sulfide, replacing the conventional hydrogen sulfide removal process was proposed. To achieve this goal, thermodynamics of this reaction was analyzed and a solid oxide electrochemical cell based on proton conducting ceramic was fabricated for operating at high temperature and using perovskite structured electrodes. Experiments were then conducted to decompose hydrogen sulfide using fabricated cells and found that about 40 ppm, 100 sccm of hydrogen sulfide was decomposed at 600 oC by applying 0.5 V, 0.57 mA/cm2. Through this, the feasibility of the process was confirmed, and the durability test and regeneration process of the anode electrode were proceeded to solve degradation caused by sulfur deposits. In this study, a process has been proposed to effectively produce hydrogen of high value as an energy source, as well as to remove industrial waste hydrogen sulfide. It is expected that waste disposal and energy source production can be simultaneously produced in a clean and efficient way if cell performance improvement, removal of sulfur poison, and large systemization are applied to oil refiners' processes.