Light harvesting and charge management by Ni₄S₃ modified metal-organic frameworks and rGO in the process of photocatalysis

Harvesting and charge management is obtained by means of Ni₄S₃ modified Metal-organic Frameworks (MOF) and rGO, namely, the Uio-66 (Zr)/rGO combined with Ni₄S₃ photocatalyst was successfully prepared with the solvothermal method. The Ni₄S₃ acted as the electron transfer agent greatly improve the electrons transmission from the excited state dye to the rGO/MOF surface for proton reduction reaction. The hydrogen production amount over EY-sensitized rGO/MOF/Ni₄S₃ photocatalyst has reached 280 μmol for 5 h, which is about 14 times than that of the pure Ni₄S₃ photocatalyst and 185 times than that of the pure rGO/MOF photocatalyst under visible light irradiation (λ ≥ 420 nm). In the composite, the rGO acts as electron-transfer mediator and Ni₄S₃ serves as H₂-evolution active site. A series of studies shown that the Ni₄S₃ modified MOF and rGO provided more active sites and improved the efficiency of photo-generated charge separation by means of several characterizations such as SEM, XRD, XPS, Element Mapping, UV-vis DRS, BET, Photocurrent, Voltammetric Scanning, Fluorescence Spectra and FTIR. and the results of which were in good agreement with each other. The photoelectron migration rate and photogenerated charge separation efficiency of the composite can be obviously increased with graphene as a good electron acceptor and transfer medium and Ni₄S₃ as hydrogen producing active site.