Influence of Atmospheric Plasma Spray Coating in Electrode Properties to Use in Alkaline Electrolysis

Kurzfassung

Hydrogen has been increasingly used as an energy carrier over the past few years due to its several applications mainly associated with the use of renewable energy. Among all the processes for hydrogen production, water electrolysis produces the purest hydrogen. However, the usage of water electrolysis accounts to only 4% of today’s hydrogen production, mainly due to economic factors. Alkaline electrolysis is, so far, the most mature, the most efficient and the simplest process among the different types of electrolysis. Nevertheless, improvements in the process are still needed, especially in decreasing the cost of the process. Nickel is one of the cheapest metals having also high electroactivity for oxygen and hydrogen production reactions. Raney-nickel materials, which are porous Ni, are the most promising electrocatalysts providing a wide surface area for the reactions to take place. Ni substrates coated with Raney-nickel NiAlMo using Atmospheric Plasma Spraying (APS) are promising stable cathodes due to the reduction of 0.226 V in hydrogen evolution reaction and its stability for, at least, 40 days. Cathodes produced with different APS parameters proved that high speed plasma jet at 580 m.s-1 creates the most stable and electrochemically active coating. Ni substrates coated with Raney-nickel NiAl coating were used for anodes. An increase of surface area towards uncoated Ni was achieved with porous NiAl. Adding Co3O4 to the NiAl coating a decrease in 0.1 V for oxygen evolution and a stable sample that lasted for 35 days was achieved, mainly due to the presence of Co. Underpotential deposition, as technique to calculate the surface area of a Ni electrode was studied. As expected, Ag was adsorbed in the Ni surface, which was identified by the several increases in current during the cyclic voltammogram cycles due to oxidations and reductions of adsorbed Ag.