Noble-metal free photocatalytic hydrogen generation of CuPc/TiO2 nanoparticles under visible-light irradiation

Development of visible-light activated photocatalysts is highly important but challenging for photocatalytic reactions. In addition, noble-metal cocatalysts are crucially required for efficient charge transfer in most solar water splitting reactions. In the present study, we have synthesized copper phthalocyanine (CuPc) supported TiO2 photocatalyst composites by a facile solution reaction and demonstrated their efficient photocatalytic hydrogen generation under visible-light irradiation. The amorphous CuPc coating layer plays key roles in solar water splitting in terms of efficient separation of the photogenerated charges and high absorption in visible-light region. More surprisingly, our CuPc/TiO2 does not demand any noble-metal cocatalyst for exhibiting high photocatalytic activity with 6.68% of apparent quantum yield (AQY) at 420 nm. Moreover, several continuous runs of hydrogen generation using CuPc/TiO2 composite proved the high durability of our products. The detailed charge transfer dynamics of CuPc/TiO2 composites by time-resolved photoluminescence (TRPL) demonstrated that our noble metal-free CuPc/TiO2 shows a comparably high charge transfer efficiency as that of Pt cocatalyst modified samples. On the basis of the analysis, a possible mechanism for visible-light driven photocatalytic hydrogen generation of CuPc/TiO2 composites is postulated. Our study suggests that CuPc/TiO2 is a highly efficient and stable photocatalyst for solar water splitting even without noble-metal cocatalysts.