Making g-C3N4 ultra-thin nanosheets active for photocatalytic overall water splitting

The photocatalytic solar water splitting with Pt loaded graphitic carbon nitride (g-C3N4) and without sacrificial reagent is still a big challenge. In this work, g-C3N4 nanosheets were exfoliated for the first time by a femtosecond pulsed laser. After loaded with 1.4 wt.% of Pt, g-C3N4 becomes active towards the overall water splitting with a production rate of 42.6 μmol/g/h for H2 and 18.7 μmol/g/h for O2 (H2/O2 = 2.28). Compared to inactive ultrathin g-C3N4 nanosheets from conventional exfoliation, our experiments and density functional theory (DFT) calculations revealed that the cyano (-C≡N) defects created by laser pulses favor the anchoring of Pt atoms. These divalent atomic Pt cocatalysts, distinct from Pt metal nanoparticles, not only provide more active sites for the surface reaction but also largely suppress the backward reaction of water splitting. In addition, the -C≡N defects shift down the band edge positions, thus enhancing the oxidizing power of holes.