Multi-functional Ni3C cocatalyst/g-C3N4 nanoheterojunctions for robust photocatalytic H2 evolution under visible light

Developing highly active, non-noble-metal H2 evolution co-catalysts is appealing yet still remains a great challenge in the promising field of visible-light-driven photocatalytic solar fuel H2 production. In this work, high quality hexagonal Ni3C nanoparticles were facilely fabricated through the low-temperature thermolysis of nickel acetylacetonate in oleylamine under a nitrogen atmosphere and were then coupled with g-C3N4 by a simple grinding method. The photocatalytic performances of g-C3N4/Ni3C nanoheterojunctions were tested under visible light irradiation using triethanolamine (TEOA) as a hole scavenger. The optimal H2-production rate of 15.18 μmol h−1 over 15 wt% Ni3C nanoparticle decorated g-C3N4, corresponding to an apparent quantum yield (AQY) of 0.40% at 420 nm, is approximately 116.7 times higher than that of pure g-C3N4 and is even larger than that of the 0.5 wt% Pt/g-C3N4 sample. Well resolved density functional theory (DFT) calculation reveals that the “TOP” site of Ni3C(113) with a H adsorption energy of −0.97 eV is likely the dominant reaction site for H2 evolution, rather than the Hollow and Bridge sites. It was also demonstrated by the polarization curves that the Ni3C nanoparticles could act as multi-functional electrocatalysts to improve the kinetics for water oxidation, the oxidation of TEOA, and hydrogen evolution in both acidic and basic media. Therefore, the loading of multi-functional Ni3C cocatalyst nanoparticles onto g-C3N4 can fundamentally promote the rapid transportation/separation of charge carriers, enhance the oxidation kinetics of TEOA, and decrease the overpotential of H2-evolution, thus favoring significantly enhanced photocatalytic activity. It is highly expected that this work will provide new ideas to develop robust metal carbides as noble-metal-free cocatalysts for high-efficiency and low-cost g-C3N4-based photocatalytic water splitting.