Imidazole substituted Zinc(ii) phthalocyanines for co-catalyst-free photoelectrochemical and photocatalytic hydrogen evolution: influence of the anchoring group

Novel zinc phthalocyanine derivatives, ZnPc-1 and ZnPc-2, consisting of one and four imidazole units, respectively, have been synthesized and utilized as panchromatic photosensitizers for photocatalytic and photoelectrochemical H2evolution. The effect of the imidazole-anchoring group on the photocatalytic H2production has been compared with ZnPc-3, which possesses a carboxylic acid unit as the anchoring group. ZnPc-1/TiO2shows the best photoactivity with the highest H2evolution rate of 0.4006 mmol g−1h−1, which is much higher than that of ZnPc-2/TiO2and ZnPc-3/TiO2(0.3319 mmol g−1h−1and 0.3555 mmol g−1h−1, respectively). After 20 h of irradiation, ZnPc-1 produces an H2production rate of 3.4187 mmol g−1with a turnover number (TON) of 14863 and a solar-to-hydrogen energy (STH) conversion efficiency of 1.03%, without using a co-catalyst.