Dual Functionality of Mixed Cu-based Two-Dimensional (2D) Heterostructures Derived from Electronic Wastes

Growing concerns on non-renewable fossil fuel resources and anthropogenic emissions of greenhouse gases have drawn attention to the development of sustainable and renewable energies through the use of functional nanostructures. A sustainable approach that can yield multiple advantages is the engineering of nanostructures from recycling of electronic waste (e-waste) materials. The present work reports a simplified, high-yield, and controllable strategy to fabricate Cu-based heterojunction ultrathin films with a stratified structure, in which the number, composition, and structure of layers can be tailored, through an assembly of two-dimensional (2D) Cu-based nanosheets. As electrodeposited, the bilayer Cu/Cu2O-Cu(OH)2 exhibited a pseudocapacitance behaviour, showing high power density with a promising potential for energy storage applications. Rapid, low-temperature thermal treatment then led to a partial transformation of Cu and Cu2O-Cu(OH)2 layers into CuO, resulting in the formation of a trilayer heterojunction ultrathin film with high energy harvesting performance as a photocathode for hydrogen production, where the significantly improved electron/hole separation and increased number of active sites across the interfacial regions resulted in an outstanding photoelectrochemical current density of 2.6 mA·cm-1 at -0.6 V vs. Ag/AgCl. Lastly, a Life Cycle Assessment (LCA), comparing three different scenarios from which the pristine material is obtained (i.e., recycled or pure resources), was conducted to evaluate environmental impacts associated with the recycling and production processes of such nanomaterials. The LCA results highlighted the importance of such value-added recycling on the environment, and the immense potential of e-waste applicability in developing advanced functional nanomaterials.