CoMn-S/CDs nanocomposite for effective long wavelength visible-light-driven photocatalytic water splitting

Abstract

Photocatalytic water splitting to produce hydrogen is one of the important ways to solve energy crisis. Most transition metal sulfide semiconductors which have wide optical band gap are impractical for long wavelength visible light driven water splitting. Therefore, modulation of broad band gap has become a significant strategy and a huge challenge to achieve efficient catalyst for photocatalytic water splitting. Here, we report the synthesis of a ternary photocatalyst MnS/CoS2/CDs applied for long wavelength visible-light-driven water splitting without the requirement for any sacrificial agents. The optimal MnS/CoS2/CDs nanocomposite (CoMn-S/CDs) as an effective photocatalyst exhibits excellent photocatalytic activity with H2 evolution rate of 0.421 μmol/h and O2 evolution rate of about 0.051 μmol/h under visible light irradiation (420 nm ≤ λ ≤ 700 nm) when the concentration of CDs is 0.039 gCDs/gcatalyst. In particular, the H2 evolution rate is 0.076 μmol/h and O2 evolution rate is about 0.010 μmol/h at λ = 535 nm while the H2 evolution rate is 0.024 μmol/h and O2 evolution rate is about 0.004 μmol/h at λ = 630 nm. The efficient photocatalytic activity may attribute to the synergistic effect of the ternary sturctures, in which MnS is the major component for photocatalysis, addition of CoS2 component enables the photocatalyst to capture light of wider range and CDs provide reduction sites.