Synergistically improved charge separation in bimetallic Co–La modified 3D g-C3N4 for enhanced photocatalytic H2 production under UV–visible light

Abstract

Synergistically improved Lanthanum (La) and Cobalt (Co) co-modified g-C3N4 was synthesized for photocatalytic H2 generation from methanol-water mixture under UV–visible light irradiation. The g-C3N4 was synthesized by thermal polymerization and co-modification was carried out by wet impregnation method. Photocatalytic H2 production by Co2/La1-g-C3N4 was carried out in a slurry photoreactor with the highest H2 production of 250 μmol g−1h−1, which was 2.5, 1.35, and 1.25 times increased as compared to pristine g-C3N4, La1-g-C3N4, and Co2-g-C3N4, respectively. The enhanced activity can be associated with the synergistic effect for proficient charge separation due to electron trapping ability of Co and La, and C–H bond cleavage ability of La for enhanced oxidation. Among the sacrificial agents, highest H2 generation rate was observed with triethanolamine which generated 8.1, 3.6, 1.7, 2.4, and 4.2 times boosted H2 generation than water, ethanol, methanol, ethylene glycol, and glycerol, respectivel, because of the effectual binding of triethanolamine onto amine-containing g-C3N4. Moreover, it also depicted good photostability towards photocatalytic H2 generation. Therefore, Co and La co-modification was proved to be effective for efficient charge separation and reduction of charge carrier's recombination and would be beneficial for other solar energy applications.