Rational design of cocatalyst system for improving the photocatalytic hydrogen evolution activity of graphite carbon nitride

Abstract CoS-Co(OH)2 heterostructure with conductive polypyrrole (PPy) as charger transfer mediator were rationally designed and embedded onto the g-C3N4 photocatalyst as the dual noble-metal-free cocatalyst for the first time, for improving the transport, separation and utilization efficiency of the photo-generated charge carriers. Notably, CoS, acting as photocatalytic hydrogen production cocatalyst, not only facilitated the utilization of charge carriers, but also accelerated the charge separation owing to its lower flat band potential. Furthermore, Co(OH)2 photocatalytic oxygen production cocatalyst exhibited a synergistic effect with CoS for further improving the charge carriers utilization efficiency. Consequently, g-C3N4-PPy, ternary g-C3N4-PPy-CoS and quaternary g-C3N4-PPy-CoS-Co(OH)2 heterostructures exhibited the photocatalytic hydrogen production activities of 2.49, 23.27 and 46.67 μmol/h, which were 17, 155 and 311-fold in comparison with that of pristine g-C3N4, respectively. This work provided a hopeful insight for the design of high performance cocatalyst for improving the transport, separation and utilization of photo-exited charge carriers.