Modifications for the improvement of catalyst materials for hydrogen evolution

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 ac- tivity 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, TiO 2 was con- verted into the crystalline form and multiwall carbon nanotubes (MWCNTs) were used instead of carbon particles. The improvement, expressed in terms of the lower- ing 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 TiO 2 (TiO 2 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 sys- tems remained superior HER catalysts.