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.