Preparation of Bifunctional CuWO4-Based Heterostructure Nanocomposites for Noble-Metal-Free Photocatalysts

This article describes the preparation of copper tungstate (CuWO4)-based heterostructured nanocomposites by facile two-step polyol assisted hydrothermal-annealed process. A series of characterization techniques (FESEM, EDS, HRTEM, XPS, XRD and FTIR etc.) were confirmed the formation of typeI I (CuWO4/ WO3 center dot 0.33H(2)O; CuWO4/WO3) and type-II (CuWO4/Cu2O; CuWO4/Cu2O/CuO; CuWO4/CuO) heterojunction as function of pH and annealing temperatures. Also WO3 center dot 0.33H(2)O, WO3, Cu2O, Cu2O/CuO and CuO were found as secondary phases with CuWO4. These nanocomposites exhibited the enhanced visible light absorption and the band gap (ca. 1.7 eV) of CuWO4 is smaller than the early reported value (2.1-2.3 eV). In photocatalytic degradation, the CuWO4/Cu2O/CuO and CuWO4/WO3 center dot 0.33H2O were showed 1.66 fold times higher and nearly equal apparent rate constant respectively than that of CuWO4. In photoelectrochemical (PEC) studies, the CuWO4/Cu2O, CuWO4/Cu2O/CuO, CuWO4/WO3 and CuWO4/CuO nanocomposites showed more photocurrent density of 3.5, 2.2, 0.71 and 0.41 mA/cm(2) at 1.23 V-RHE respectively than CuWO4. The existence of dual co-catalysts (Cu2O and CuO) with CuWO4, strongly promote the electronhole pair separation and migration. Among the nanocomposite, the CuWO4/CuO was showed the similar static photocurrent as that of CuWO4 under 1 Sun illumination. The advantage of present work is noble-metal-free photocatalysts prepared with binder free, less time, low energy consumption and cost, and environmental benign.