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, λ > 420 nm) or near infrared (NIR, λ > 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 H2. 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 μmol 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 μmol 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.