g-C3N4 modified by pyropheophorbide-a for photocatalytic H2 evolution

Protonated g-C3N4 (pCN) was modified by pyropheophorbide-a (Ppa) to prepare a Ppa/pCN catalyst for photocatalytic hydrogen production under visible-near infrared (VIS-NIR, lambda > 420 nm) or near infrared (NIR, lambda > 780 nm) irradiation. Ppa/pCN has enhanced light absorption compared with pCN, as seen in ultraviolet-visible and near-infrared (UV-vis-NIR) absorption spectra. Transient photocurrent response data, electrochemical impedance spectra (EIS), and electron spin resonance (ESR) spectra showed that Ppa/pCN can effectively separate and transport photogenerated electron-hole pairs, and the electrons are used to reduce H2O to produce H-2. When Pt was used as a co-catalyst and triethanolamine (TEOA) was used as a sacrificial reagent, an average hydrogen evolution rate of 1,093.0 mu mol g(-1) h(-1) can be achieved using the Pt-Ppa/pCN-TEOA combination under VIS-NIR irradiation, much higher than the rate (290.4 mu mol g(-1) h(-1)) achieved by using the Pt-pCN-TEOA combination. A possible mechanism of photocatalytic H2 evolution and electron transfer for Ppa/pCN was proposed.

Automated summary

The modification of protonated g-C3N4 (pCN) with pyropheophorbide-a (Ppa) resulted in the preparation of a Ppa/pCN catalyst, exhibiting enhanced light absorption and efficient separation and transportation of photogenerated electron-hole pairs for improved hydrogen production under visible or near-infrared irradiation. The combination of Pt-Ppa/pCN-TEOA showed a significantly higher average hydrogen evolution rate compared to Pt-pCN-TEOA, suggesting a promising photocatalytic mechanism for enhanced H2 production.