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Modifications for the improvement of catalyst materials for hydrogen evolution

Paunović Perica (Tehnološko-metalurški fakultet, Univerzitet 'Sv. Ćirilo i Metodije'; Skopje i Vojna akademija 'General Mihailo Apostolski', Skopje, Republika Makedonija)
Popovski Orce (Tehnološko-metalurški fakultet, Univerzitet 'Sv. Ćirilo i Metodije'; Skopje i Vojna akademija 'General Mihailo Apostolski', Skopje, Republika Makedonija)
Jordanov Hadži Svetomir (Tehnološko-metalurški fakultet, Univerzitet 'Sv. Ćirilo i Metodije'; Skopje i Vojna akademija 'General Mihailo Apostolski', Skopje, Republika Makedonija)
Dimitrov Aleksandar (Tehnološko-metalurški fakultet, Univerzitet 'Sv. Ćirilo i Metodije'; Skopje i Vojna akademija 'General Mihailo Apostolski', Skopje, Republika Makedonija)
Slavkov Dragan (Tehnološko-metalurški fakultet, Univerzitet 'Sv. Ćirilo i Metodije'; Skopje i Vojna akademija 'General Mihailo Apostolski', Skopje, Republika Makedonija)

The structural and electrocatalytic characteristics of composite materials based on non-precious metals were studied. Precursors of metallic phase (Ni, Co or CoNi) and oxide phase (TiO2) were grafted on a carbon substrate (Vulcan XC-72) by the sol-gel procedure and thermally treated at 250 ºC. Ni and CoNi crystals of 10-20 nm were produced, in contrast the Co and TiO2 were amorphous. The dissimilar electronic character of the components gives rise to a significant electrocatalytic activity for the hydrogen evolution reaction (HER), even in the basic series of prepared materials. Further improvement of the catalysts was achieved by modification of all three components. Hence, Mo was added into the metallic phase, TiO2 was converted into the crystalline form and multiwall carbon nanotubes (MWCNTs) were used instead of carbon particles. The improvement, expressed in terms of the lowering the hydrogen evolution overpotential at 60 mA cm-2, was the most pronounced in the Ni-based systems grafted on MWCNTs (120 mV lower HER overpotential) compared to 60 mV in case of Ni-based systems grafted on crystalline TiO2 (TiO2 prepared at 450 ºC) and of Ni-based systems containing 25 at.% Mo. Nevertheless, even with the realized enhancement, of all the tested materials, the Co-based systems remained superior HER catalysts.

Keywords: composite electrocatalysts, hydrogen evolution, electronic interaction, real surface area