P/S-g-C3N4 nanosheet composites with enhanced photocatalytic water splitting and dye degradation

The band gap and photo- and electro-chemical activities of graphic carbon nitride (g-C ₃N ₄) depended strongly on their components. In this paper, P-g-C ₃N ₄/S-g-C ₃N ₄ (PCN/SCN) and S-g-C ₃N ₄/P-g-C ₃N ₄ (SCN/PCN) composite nanosheets heterostructures were created using P-doped and S-doped g-C ₃N ₄ nanosheets as seeds to study the effect of compositions on photo- and electro-chemical properties. Thermal polymerization temperature and the ratios of S- and P-doped g-C ₃N ₄ components were adjusted to get optimized conditions. The photo-degradation kinetics of Rhodamine B (Rh B) and photocatalytic H ₂ generation were used to discuss the relationship of photocatalytic performance and composition of photocatalysts. The degradation of Rh B in visible light region was finished using sample 600MCNS@ 720 DCNP15% within 15 min with a degradation rate constant of 0.197, which was 2.3 and 3.9 times compared with S- and P-doped g-C ₃N ₄ nanosheets, respectively. Namely, the H ₂ generation rate of sample 600MCNS@ 720 DCNP15% was 1851.9 µmolg ⁻¹h ⁻¹, which is 6.6 and 5.9 times higher than those of S- and P-doped g-C ₃N ₄ nanosheets, respectively. Interestingly, these P/S-g-C ₃N ₄ composite heterojunctions revealed improved electro-chemical performance. In the case of a current density of 1 mA cm ⁻², the overpotential of ample 600MCNP@ 720 DCNS20% was 333 mV and a Tafel slope was 155.33 mV dec ⁻¹ in KOH solutions. This result supplied an efficient approach to improve the photocatalytic performance of g-C ₃N ₄ based materials.