Efficient visible-light photocatalytic H2 evolution over metal-free g-C3N4 co-modified with robust acetylene black and Ni(OH)2 as dual co-catalysts

In this work, a novel g-C3N4/acetylene black (AB)/Ni(OH)(2) ternary composite photocatalyst with dual robust electron co-catalysts was successfully synthetized using a facile two-step strategy: ultrasonic dispersion treatment and a subsequent precipitation process. The photocatalytic H-2-production activity over the composite photocatalyst was also evaluated using an aqueous solution containing triethanolamine under visible light (lambda >= 420 nm). For the first time, it was revealed that the robust AB can be utilized as a cocatalyst to significantly enhance the photocatalytic H-2-evolution activity of g-C3N4. The results also demonstrated that the ternary g-C3N4/AB/Ni(OH)(2) nanocomposite exhibited enhanced photocatalytic H-2-evolution activity as compared to bulk g-C3N4 and binary hybrids. The g-C3N4-0.5% AB-1.0% Ni(OH)(2) (weight ratio) composite shows the highest H-2 evolution rate of 240 mu mol g(-1) h(-1) under visible light irradiation, which is 320, 100 and 3.31 times higher than that of pure g-C3N4, g-C3N4-0.5% AB and g-C3N4-1.0% Ni(OH)(2), respectively. It is believed that the excellent synergetic effect between the robust AB and Ni(OH)(2) as dual electron co-catalysts on the surface of g-C3N4 can achieve the effectively promoted separation of photo-generated electron-hole pairs and enhance the following H-2-evolution kinetics, thus resulting in a significant enhancement of the photocatalytic H-2 evolution activity over g-C3N4. It is expected that the combination of nano-carbons such as AB and other earth-abundant co-catalysts can become a general strategy to improve the H-2-evolution activity over various kinds of conventional semiconductors.