The present invention relates to a method of preparing a catalytic structure the method comprising the steps of: providing a solution of a precursor compound in a solvent at ambient conditions; providing a suspension of a support material having a specific surface area of at least 1m 2/g in a solvent at ambient conditions; optionally sonicating the suspension of the support material; mixing the solution of the precursor compound and the suspension of the support material; providing a reactive solvent in a supercritical or subcritical state; admixing the mixture of the solution of the precursor compound and the suspension of the support material in the supercritical or subcritical reactive solvent to form a reaction solution; injecting the reaction solution into a reactor tube via an inlet allowing a reaction of the precursor compound in the supercritical or subcritical reactive solvent in there actor tube to form the catalyst nanoparticles on the support material to provide the catalytic structure; and withdrawing the catalytic structure from the reactor tube via an out- let. The catalytic structure is suitable for use in fuel cells.
