Electrocatalysis: Synthesis to Devices

Materials

MXenes

MXenes are a relatively new family of 2D materials (1 to 3 layers), which are made up of transition metal carbides and nitrides, produced from MAX phases by various etching processes, Figure X. A MAX phase has the general formula of Mn+1AXn where the M is an early transition metal, the A is an element from group 13 and 14 of the periodic table, and the X represents a carbon or nitrogen. During the etching process, done in a fluoride ion based solution, the element from group 13/14 is removed from the MAX structure causing the carbide layers to become terminated by OH-, O- , Cl- or F- groups which are subsequently called ‘surface groups or edge sites’.5 The resulting structure is known as a ‘MXene’. MXenes are known to be highly conductive and durable due to their structures. However, to date MXenes are not known to contain active sites for the OER, as no MXenes with metals for promoting the OER (e.g. Mn or Fe) have been successfully synthesised.  On the other hand, Transition metal oxides (TMOs) are an exciting group of materials that possess various intriguing physical properties that can change depending on the oxidation state of the material and are known to be active water splitting catalysts. By combining inexpensive, active TMO catalyst with MXenes, Our group creates catalyst layers with characteristics of a desired OER catalyst.

Synthesis

MXenes are ideal substrates for OER-active materials because of their high surface area and excellent hydrophilicity, which boost OER activity by increasing the number of exposed active sites. Aiming to produce compounds with enhanced electrocatalytic activity for conversion reactions, we functionalize the surface of MXene with transition-metal-based materials using wet chemical synthesis techniques. This strategy enables precise control over the composition, morphology, and structural properties of the resulting materials.

Our methods include hydrothermal and solvothermal techniques for the growth of well-defined crystalline materials under controlled temperature and pressure, precipitation and co-precipitation methods for tunable stoichiometry and homogeneous particle formation, the polyol method for producing well-dispersed nanoparticles with controlled size and shape, and microwave-assisted synthesis to accelerate reaction kinetics for enhanced material uniformity. Additionally, we use electrodeposition for the controlled deposition of materials directly onto conductive substrates, ensuring uniformity and high adhesion.