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 A_1g and E_Ag ¹ at 150 cm⁻¹ and 250 cm⁻¹ asserted the presence of WSe₂ in WC which exhibited A_1g 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.