The photo is sourced from rscf.ru
Electrolysis – decomposing water molecules into hydrogen and oxygen under the impact of electric current – requires the use of catalysts that significantly speed up chemical processes. Platinum metal is considered to be the best of these, but scientists are looking for less expensive alternatives, one of which is molybdenum disulfide (MoS2) – a gray-blue crystalline powder, oily to the touch. However, only one of its modifications exhibits high catalytic activity, which decreases when heated to 80 degrees Celsius, an inevitable level for industrial conditions.
The research of the Russian scientists was intended to answer the following question: how to increase stability of molybdenum disulfide so that to improve its catalytic properties? Depositing a negatively charged material on MoS2 monolayers became the solution.
The crystal lattice of molybdenum disulfide consists of S-Mo-S (sulfur-molybdenum-sulfur) layers of three-atom thickness. Molybdenum and sulfur atoms inside these layers are linked by covalent chemical bonds, and the layers themselves are linked due to the so-called van der Waals interactions – intermolecular forces that are weaker than a chemical bond. This structure makes it possible to separate MoS2 crystals into separate layers as well as to obtain the systems, in which molybdenum disulfide layers alternate with other components. This gave researchers the opportunity to build between the layers of anions (negatively charged ions) MoS2 “stuffing” of organic cations (positively charged ions) strongly associated with sulfide layers due to electrostatic and non-covalent interactions.
The authors of the research conducted a thousand continuous cycles of water splitting, during which the catalyst activity remained unchanged due to the built-in organic layers. Some samples remained stable even at the temperatures of 150-200 degrees Celsius. “We hope that the data obtained in this research will help to find a new approach to the design of MoS2-based catalysts for hydrogen production without emitting carbon dioxide,” the Russian Science Foundation quotes Alexander Golub, PhD in chemistry, the project leader.