Electrodeposition – the technique of choice for advanced coatings

Electrodeposition is an old technique with a blooming present and promising future. Indeed, the first steps of electrodeposition can be traced back to around 1800. It is an electrochemical process that allows the deposition of solid deposits on the surface of conductive materials, also called substrates. Although metal oxides, semiconductors, polymers, and even metal-organic frameworks can be grown by electrodeposition, it is mostly utilised for the preparation of metals and metal alloys via cathodic electrodeposition.

Electrodeposition (or electroplating as it is widely known in the metal plating industry) has evolved from an art to an exact science thanks to the number of applications electrodeposited metallic materials possess. This is in part due to the immense possibilities that electrodeposition offers in terms of material dimensionality (thin and thick layers, nanowires, nanotubes, nanoparticles, etc.) and the fact that the set-up is rather simple and the process works at room pressure and often at room temperature. Hence, it is a relatively low-cost technique.

 

Electrodeposition can be performed from aqueous and non-aqueous electrolytes such as conventional organic solvents, ionic liquids, deep eutectic solvents, and molten salts. Hence, a large list of transition metals and alloys is accessible in the end by electrodeposition. For example, aluminium metal cannot be electroplated from aqueous solutions, but it can be deposited from ionic liquids.

 

Most importantly, electrodeposition works on both flat and patterned substrates. The latter allows the growth of matrices of micron, submicron, and nanoscale motifs if the substrates are previously patterned using optical or e-beam lithography. The use of alumina and track-etched polymer templates has become immensely popular in the last decades for the growth of nanowires and nanotubes, and this has greatly helped electrodeposition regain credibility and even attract researchers from other disciplines.

 

The design and preparation of electrocatalysts for hydrogen evolution reaction (HER), oxygen reduction reaction (ORR) or carbon dioxide reduction by electrodeposition is today’s reality. Provided that the substrate is conductive, a variety of electroactive materials can be successfully deposited (e.g., Pt, Ni, Co, their alloys, and related composites).

Current trends seek to remove Pt partially or fully from the catalyst composition without severely compromising its catalytic activity and stability. Several strategies are on the way, and the dream of a Pt-free cheap and durable electrocatalyst will become a reality sooner or later.