Fabrication of NiCo2S4/N-deficient g-C3N4 for efficient photocatalytic H2 production

Graphitic carbon nitride (g-C3N4) as an ideal visible light active photocatalyst has received much attention in the fields of photocatalytic H2 production, pollutant degradation, and CO2 reduction due to its excellent stability and environment friendly features. In this work, g-C3N4 with N-defects (C3N4-x) was obtained through a KOH-assisted hydrothermal strategy followed by a freeze drying and an annealing process using urea as the starting materials. The investigation shows that C3N4-x has a narrower band gap of 2.7 eV, lower zeta potential of -25.9 mV, more negative CB position of -0.97 V and active sites compared to ordinary bulk g-C3N4, these all contribute to the improved activity for photocatalytic H2 evolution. Furthermore, the activity of C3N4-x was further improved by introduction of H2 evolution co-catalyst NiCo2S4 on its surface via a solvent evaporation method. The H2 evolution rate of 20% NiCo2S4/C3N4-x can reach up to 15673 μmol·g−1·h−1 under a 300 W Xe lamp in TEOA solution, which is 92 times for g-C3N4 (170 μmol·g−1·h−1), 46 times for C3N4-x (340 μmol·g−1·h−1), respectively. It is found that the introduction of NiCo2S4 can increase the number of active sites, prolong the carrier lifetime, decrease the H2 evolution potential of the sample, and improve contact between reaction solution and catalyst surface. This work suggests that transition bimetallic sulfides might be suitable H2 evolution co-catalyst for the g-C3N4-based photocatalytic H2 production systems.