Investigation of kinetic mechanisms of photocatalytic hydrogen generation from formic aside using metal-ceramic composites under visible-light irradiation

Processes of photocatalytic hydrogen generation from the formic acid water solution under vis-light irradiation with tantalum contained metal-ceramic silicon nitride-based composites were investigated depending on pH of the solution and hydrogen peroxide adding. These compounds were obtained by self-propagated high temperature (SHS) synthesis in the way of the ferrosilicoaluminum (FSA) and silicon-aluminum powders ignition in a nitrogen atmosphere with the tantalum addition. During the investigation it was found out that the reaction rate of the hydrogen production without hydrogen peroxide can be described within the Langmuir–Hinshelwood mechanism. There is the reaction mechanism changing simultaneously with a formic acid concentration increasing in the presence of H2O2. The most significant reaction rate of hydrogen production from HCOOH is observed with the Fe-contained composite synthesized from FSA in the solution system without H2O2 addition, the reaction turns of frequency (TOF) is 4.55 µmol/min.