Bi-functional Ag-CuxO/g-C3N4 hybrid catalysts for the reduction of 4-nitrophenol and electrochemical detection of dopamine

The immense needs to build highly efficient catalysts has always been on the forefront of environmental remediation research. Herein we have synthesized a dual phase copper oxide containing Cu2O and CuO originating from the same reaction using hexamethyltetramine (HMT). Simultaneously we coupled it with g-C3N4 (g-CN) constructing a triple synergitic heterojunction which are being reported very less often in the literature. The hydrothermal reactions led to the formation of various catalysts namely Ag-Cu2O-CuO-gCN (ACCG), Ag-CuO-gCN (ACG), Ag-Cu2O-CuO (ACC) and Ag-CuO (AC). The catalysts were thoroughly characterized via XRD and FESEM to gain the structural, crystallographic and morphological insights of the catalyst. Clearly we can observe the pure phase formation of the catalyst and development of sheet like CuO and truncated octahedrons of Cu2O fused together within the g-CN framework. Also XPS studies revealed the presence of copper in two different oxidation states namely Cu2+ and Cu+. BET analysis was performed to analyze the surface area and pore volume of the catalysts which plays a very significant role in catalytic reduction. The catalytic efficiency of the catalysts was evaluated via the reduction of 100 ppm 4-Nitrophenol (4-NP) to 4-Aminophenol (4-AP) without using any light irradiation. The most efficient catalyst was ACCG revealing the reduction of 4-NP in 4 minutes. Both Cu2O and g-CN played a significant role in the reduction following a zero order kinetics unlike most often reported in literature. We also evaluated the catalytic reduction with different concentrations of 4-NP and tuning the catalyst amount as well. A mechanism was postulated based on the XRD of post catalytic reduction catalyst. The ACCG catalyst was also successfully tested as an effective dopamine sensor. The GC/ACCG electrode exhibited an oxidation peak current density of 0.28 mAcm-2 which was much higher than the other catalysts. This unique combination of pure phase materials to form composite as an effective catalyst as well as sensor is an exclusive effort towards environmental remediation.