Maximizing hydrogen peroxide formation during water electrolysis

Water is considered the most useful starting material for hydrogen production due to its easy availability. Ideally, converting water into hydrogen would produce a second useful substance, hydrogen peroxide, which is needed in many industrial sectors, such as in the production of disinfectants.

Special reaction conditions are required. hydrogen peroxide It was known that the presence of carbonates was beneficial for the splitting of water, but it was unclear why this was the case. Now a team of researchers from Ruhr University Bochum in Germany has uncovered the mechanism behind it.

The group, led by Dr. Région Li, Dr. Carla Santana Santos and Professor Wolfgang Schumann from the Center for Electrochemistry at the Ruhr University in Bochum, result In the journal Angewandte Chemie International Edition.

Kill two birds with one stone

“Hydrogen peroxide is a valuable chemical that must be produced using complex processes that are not necessarily environmentally harmless,” Schumann says.

It would be useful to obtain this substance in large quantities by electrolysis of water, which also produces the energy carrier hydrogen. “But this is thermodynamically complicated,” explains Lejing Li, because producing oxygen is, so to speak, energetically simpler.

However, this changes when a carbonate buffer is added to the solution. Carbonated (H₂CO₃), proton (H⁺), bicarbonate (HCO₃^–), and further reacted carbon dioxide (CO₂Buffers like these help keep the pH of the solution stable, but conditions in the reaction solution are not the same everywhere.

Conversion of water The reaction of hydrogen and oxygen takes place at the surface of two electrodes to which a voltage is applied. Electronic As it moves, positively charged protons are released. The protons change the pH value in the immediate vicinity of the electrode, while the pH value remains stable further away in the solution.

Local pH measurement

Using a method they developed themselves, the Bochum team measured the pH value in the immediate vicinity of the electrode under different reaction conditions and found that hydrogen peroxide is preferentially produced when there is a large amount of bicarbonate close to the electrode. Under these conditions, an intermediate reaction product is formed that prevents the production of unwanted oxygen.

“At first glance, these results sound like abstract fundamental research,” Li said. “But hydrogen and its production are Peroxide This is very important. Only if you understand the process properly can you improve it.”