Thin coatings on materials

A method for depositing a metal containing material onto a porous substrate, the method comprising:

• (a) forming a seed coating on the substrate, wherein the seed coating at least partially covers the substrate, the seed coating being substantially free of precious metal;
• and;
• (b) applying a metal containing material to the seed coating, wherein the surface area of the substrate is greater than 0.02 m2/cm3, as determined prior to coating the substrate and the metal containing material applied in step (b) forms a layer having a thickness of less than 500 nm.

A method as claimed in any one of the preceding claims wherein the initial chemically reducible metal containing material comprises a hydroxide, an oxyhydroxide or a carbonate, or mixtures of two or more thereof and wherein the initial chemically reducible metal containing material preferably comprises a nickel containing material, or a copper containing material, or a nickel containing material and a copper containing material or more preferably nickel and/or copper.

A method as claimed in any one of the preceding claims wherein at least part of the porosity in the substrate is interconnected and open to the surface and wherein the substrate preferably has a volume fraction of pores of at least 30% and more preferably at least 50%, as determined prior to coating the substrate.

A method as claimed in any one of the preceding claims wherein the substrate has a thickness of at least 1 μm and preferably at least 100 μm and more preferably in the range of from 100 μm to 500 μm.

A method as claimed in any one of the preceding claims wherein deposition of any of the coatings is carried out from a liquid that flows into at least some of the pores in the membrane and preferably the metal-containing material is applied to the substrate from the fluid that is flowed through the pores of the membrane.