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 H-2 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 H-2 evolution. Furthermore, the activity of C3N4-x was further improved by introduction of H-2 evolution co-catalyst NiCo2S4 on its surface via a solvent evaporation method. The H-2 evolution rate of 20% NiCo2S4/C3N4-x can reach up to 15673 mu mol center dot g(-1)center dot h(-1) under a 300 W Xe lamp in TEOA solution, which is 92 times for g-C3N4 (170 mu mol center dot g(-1)center dot h(-1)), 46 times for C3N4-x (340 mu mol center dot g(-1)center dot h(-1)), respectively. It is found that the introduction of NiCo2S4 can increase the number of active sites, prolong the carrier lifetime, decrease the H-2 evolution potential of the sample, and improve contact between reaction solution and catalyst surface. This work suggests that transition bimetallic sulfides might be suitable H-2 evolution co-catalyst for the g-C3N4-based photocatalytic H-2 production systems.