Photoelectrochemical properties of Pt- and Ir-modified graphitic carbon nitride

In this work, the photoelectrochemical properties of g-C3N4 modified with Pt, Ir and Ir/Pt bimetallic co-catalysts were studied. All prepared photoelectrodes were tested in a two-electrode cell by cyclic voltammetry, impedance spectroscopy, and the Mott-Schottky method. First, the optimal electrolyte (triethanolamine, NaCl, NaOH, Na2SO4) was selected. The highest photocurrents were recorded in 0.5 M Na2SO4. This electrolyte was used for the subsequent tests. Second, the photoelectrodes loaded with the noble metals are studied. It was shown that in case of monometallic co-catalysts, the deposition of noble metal is accompanied by the decrease of the short-circuit current density and the growth of open-circuit voltage. The simultaneous presence of bimetallic co-catalysts can significantly affect the semiconductor electron structure and photogalvanic properties. Some correlations between the short-circuit current density and the oxidation state of the noble metals were found. A linear correlation between Pt0/Pt0+Pt2+ and Jsc was observed. It was also shown that the presence of iridium in Ir3+ form favors the photocurrent generation. The highest values of the photocurrent were obtained for g-C3N4 and were equal to 0.57 mA/cm2.