Substituent Regulating Porphyrin Derivatives for Efficient Photocatalytic Hydrogen Evolution

Abstract

AbstractPorphyrin and its derivatives have been seen as a type of potential organic photocatalyst for photocatalytic hydrogen evolution. Substituent regulation as a simple method can effectively regulate the photoelectric characteristic of organic semiconductors. Herein, we designed three porphyrin derivatives attached with different substituents (PP‐NH2, PP‐OH and PP‐COOH). Through a facile substituent optimization strategy, the photoelectric properties of these porphyrin derivatives show an obvious difference, which leads an optimized photocatalytic hydrogen evolution efficiency. The porphyrin derivative with carboxyl presents a reduced impedance, and a better charge separation. Compared to the amino group, PP‐COOH with carboxyl, achieved a high hydrogen evolution rate of 2.20 mmol g−1 h−1 (over 20 times than that of PP‐NH2). Moreover, enhanced stability was observed in PP‐COOH rather than PP‐OH, because of the lower HOMO energy level. And the ionization of carboxyl in water negatively charges the porphyrin derivatives and forms a relatively stable sol. This result further increases the operation stability of PP‐COOH, during photocatalytic hydrogen evolution. This study presents a promising design strategy for long‐lifetime photocatalysts for hydrogen evolution.