Chinese researchers in hydrogen production breakthrough

Chinese researchers claim to have demonstrated a seawater process for producing hydrogen that works as efficiently as a commercial freshwater process.

The device, a membrane-based seawater electrolyser, helps address the corrosion problems of traditional methods.

The team, led by Zongping Shao, a chemical engineering professor at China’s Nanjing Tech University, has published their study in the journal Nature and claimed that their model “ran for over 3,200 hours under practical application conditions without failure”.

At present, salt water results in the corrosion of electrodes used in various systems, often making them unviable. The use of polyanion coatings to resist corrosion by chloride ions or highly selective electrocatalysts has not helped enough for practical applications.

A desalination process can solve the issue, “but it requires additional energy input, making it economically less attractive” according to the research. The size of the equipment involved in the desalination process also makes such solutions less flexible.

An electrolyser typically consists of two electrodes coated with catalysts, and a membrane separates the constituent components – hydrogen and oxygen. The formation of the highly corrosive chlorine gas in the process leads to catalysts and electrodes degrading faster. Magnesium and calcium ions in seawater can also block the membranes. These factors decrease the overall efficiency and life of such devices.  

The team uses a concentrated potassium hydroxide electrolyte solution to dip the electrodes, and a porous membrane helps to separate the electrolyte solution from seawater. The fluorine-rich membrane blocks the liquid water but lets the water vapor pass through.

During electrolysis, water in the electrolyte solution gets spit into its constituent components. This results in a pressure variation between the electrolyte and the seawater, causing the latter to evaporate. At the same time, the water passes through the membrane into the electrolyte and turns back into liquid water, replenishing the stock for the next cycle.

The researchers are positive that their device, along with producing hydrogen, will also be able to recover lithium from the seawater. Further applications of the device, they claim. extend to activities like cleaning industrial freshwater.