Chemically assembled 2D-van der Waals WSe2-WC heterostructured photo-anodes for electrochemical devices

Structural, optical, nanomorphological, photoresponsive and electrochemical charge transport characteristics of chemically assembled 2D-layered Tungsten Selenide (WSe2)-Tungsten Carbide (WC) heterostructure were examined. WC exhibited an optical bandgap of -3.2 eV, which did not show any optical absorption in the visible spectrum, and WSe2 showed the same in the spectral range of 200 nm-950 nm with an optical bandgap of -1.3 eV. Chemical assembly of WSe2-WC heterostructure was made in which the weight fraction of WSe2 was varied to understand its role in WC. Among the 2, 4, 6 and 8 wt% of WSe2 in WC, we observed that 6 wt% exhibited a dominant absorption and fluorescence emission (-600 nm). High-resolution transmission electron microscopic studies revealed the d-spacing values of 0.24 nm and 0.33 nm for WSe2 and WC, respectively. Further, the presence of W (4f), Se (2d) and C (1 s) were traced out and studied by X-ray photoelectron spectroscopy. Raman modes A1g and EAg 1 at 150 cm-1 and 250 cm-1 asserted the presence of WSe2 in WC which exhibited A1g at 150 cm-1. In addition, the individual WSe2 and WC along with WSe2-WC heterostructures were subjected to X-ray diffraction to study the crystallite size and strain-induced broadening due to the lattice deformation that occurred at the WSe2-WC heterostructures. Incorporating WSe2 into WC increased the photo-responsive behaviour and facilitated the charge transport as envisaged from the electrochemical impedance spectroscopic studies.

Automated summary

This study examined the structural, optical, nanomorphological, photoresponsive, and electrochemical charge transport characteristics of a chemically assembled 2D-layered Tungsten Selenide (WSe2)-Tungsten Carbide (WC) heterostructure. It was found that 6 wt% of WSe2 in WC showed dominant absorption and fluorescence emission. High-resolution transmission electron microscopy revealed the d-spacing values for WSe2 and WC, and X-ray photoelectron spectroscopy traced the presence of W, Se, and C. Raman spectroscopy confirmed the presence of WSe2 in WC. X-ray diffraction analysis showed changes in crystallite size and lattice deformation in the WSe2-WC heterostructure. The incorporation of WSe2 in WC improved photoresponsive behavior and charge transport.