Electrocatalysts with reduced noble metals aimed for hydrogen/oxygen evolution supported on Magneli phases. Part II: Electrochemical characterization

Abstract

This study is concerned with electrochemical testing of nano-scaled electrocatalysts consisted of Magneli phases as a support and different metallic phases (Co, Pt, Ru, CoPt (Co:Pt = 1:1 wt.), CoRu (Co:Ru = 1:1 wt.) and CoPtRu (Co:Pt:Ru = 1:0,5:0,5 wt.)). Electrocatalytic materials were prepared by sol-gel procedure using organometallic precursors (Me-acetylacetonate) deposited on dispersed Magneli phases in wt. ratio 10% Me and 90% Magneli phases. Electrochemical testing of the studied electrocatalysts was performed in aqueous alkaline electrolyte. The order of activity for hydrogen evolution was the following: CoPt > CoPtRu > CoRu, while for oxygen evolution: CoRu > CoPtRu > CoPt. Co has been shown as promoter for reducing Pt particles (the most active monometallic phase), so reduction of Pt quantity in the metallic phase was compensated with smaller particles. Also, mutual interaction between metallic phases (shifting the centre of d-band to values close to Fermi level) increases the intrinsic catalytic activity for both hydrogen and oxygen evolution. Due to large particle of Magneli phases, the catalytic activity is lower compared with corresponding electrocatalysts deposited on carbon nanomaterials. But, they are very good catalysts for oxygen evolution, because Magneli phases in this case, behave not only as support material, but also, as an active oxide electrode.