Biodegradable Protein-Based Photoelectrochemical Cells with Biopolymer Composite Electrodes That Enable Recovery of Valuable Metals

The development of new technologies that use sunlight as an energy source is adding to pressure on finite natural resources and the challenges of recycling and disposal. Looking to nature for material assistance, we describe a proof-of-concept flexible and biodegradable photoelectrochemical cell based almost entirely on pigments, proteins, polysaccharides, and graphene platelets. In addition to being largely environmentally benign, such devices present opportunities for the recovery of valuable components such as, in the present case, the geologically scarce metal indium and the precious metal gold. Recovery is achieved through dissolution in ethanol followed by physical separation of the heavy element, leaving a residue made up from common elements that can be recycled through natural biodegradation. Potential applications for flexible, biomolecule-based photoelectrochemical cells are considered.