The control of by-product formation rates in photocatalytic hydrogen evolution reaction from organic substances over Pt/g-C$_3$N$_4$

The results on the photocatalytic activity of 0 – 2 wt.% Pt/g-C$_3$N$_4$ in the hydrogen evolution reaction under visible light (430 nm) are presented. Triethanolamine (TEOA), glycerol, glucose and cellulose were used as electron donor. During the reaction, not only the target product, hydrogen, but also by-products of the reaction in the gas phase, namely CO and CO$_2$, were controlled. In order to study the chemical composition, microstructure and optical properties, the samples were investigated by XPS, TEM and diffuse reflection methods. The maximum hydrogen evolution rate obtained for 1% Pt/g-C$_3$N$_4$ from TEOA solution was 3.96 $\mu$mol $\cdot$ min$^{-1}$, with a selectivity of 100%. The use of glycerol and cellulose resulted in the production of syngas, and varying the platinum content allowed the selectivity of the process to vary (42.4 to 100%). Glucose using led to the formation of a mixture of CO$_2$ and H$_2$ with a selectivity of 90% or higher. In general, hydrogen-containing mixtures obtained using organic substrates can be further used in various applications.