Enhanced charge mediator properties of photocatalysts with reduced graphene nanoribbons for photocatalytic acceleration of hydrogen production in aqueous media

In this study, a hybrid photocatalyst with titanium oxide using reduced graphene nanoribbons (rGNR) was fabricated. The resulting 0.5 wt% platinum-loaded titanium oxide-supported reduced GNRs (Pt/TiO₂/rGNR) exhibited an activity of 2.54 mmol h⁻¹ g⁻¹ which is 6.35 times higher than the 0.40 mmol h⁻¹ g⁻¹ of the titanium oxide photocatalyst. This activity was also higher than that of the starting material, multi-walled carbon nanotube (MWCNT)-supported titanium oxide (Pt/TiO₂/MWCNT) as 0.80 mmol h⁻¹ g⁻¹. The resulting catalysts were characterized by X-ray photoelectron spectroscopy (XPS) and fluorescence lifetime spectroscopy, and the GNRs chemically reduced by NaBH₄ (rGNR) had higher conductivity than the GNRs reduced by photogenerated electrons (pGNR) from titanium oxide. It was found using the photocatalytic reaction and photocurrent test that almost no photoresponsivity of reduced GNR character was exhibited. This result clarified that the reduced GNRs played the role of a mediator that promotes charge separation between photocatalysts and that effective hydrogen production in water was achieved.