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

Abstract

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 H₂ evolution. The effect of the imidazole-anchoring group on the photocatalytic H₂ production has been compared with ZnPc-3, which possesses a carboxylic acid unit as the anchoring group. ZnPc-1/TiO₂ shows the best photoactivity with the highest H₂ evolution rate of 0.4006 mmol g⁻¹ h⁻¹, which is much higher than that of ZnPc-2/TiO₂ and ZnPc-3/TiO₂ (0.3319 mmol g⁻¹ h⁻¹ and 0.3555 mmol g⁻¹ h⁻¹, respectively). After 20 h of irradiation, ZnPc-1 produces an H₂ production rate of 3.4187 mmol g⁻¹ with a turnover number (TON) of 14863 and a solar-to-hydrogen energy (STH) conversion efficiency of 1.03%, without using a co-catalyst.