Hydrogen from Water over Openly‐Structured Graphitic Carbon Nitride Polymer through Photocatalysis

Abstract Openly‐structured g‐C 3 N 4 microspheres (CNMS) are developed through a well‐controlled strategy. These materials have unique features of open 3 D structure, ordered hierarchical porosity, and improved optical and electronic properties. Hydrogen evolution from water is performed under a 300 W Xe lamp with a cut‐off filter ( λ >420 nm) and Pt nanoparticles are used as the co‐catalyst (3.0 wt %). The catalyst prepared at 600 °C (CNMS‐600) has a hydrogen evolution rate (HER) of 392 μmol h −1 (apparent quantum yield, AQY=6.3 %) at 420 nm. This value is higher than that of g‐C 3 N 4 nanosheets prepared through thermal oxidation, liquid exfoliation, or chemical exfoliation. The HER value is only 27 μmol h −1 (AQY=0.43 %) at 420 nm for bulk g‐C 3 N 4 from melamine. The evolution of openly‐structured CNMS was investigated by TEM, FTIR, and XRD. The improved optical and electronic properties were demonstrated through UV/Vis absorption spectra, valence‐band X‐ray photoelectron spectroscopy, photoluminescence spectroscopy, electron paramagnetic resonance spectroscopy, and electrochemical impedance spectroscopy.