Layered franckeite and teallite intrinsic heterostructures: shear exfoliation and electrocatalysis†
Research into van der Waals heterostructures (vdWH) has been mostly focused on fabricating individually stacked atomically thin crystals in lab settings. Interestingly, vdWH materials are also readily available from the Earth's lithosphere. Franckeite is a naturally-occurring misfit-layered vdWH, composed of Pb, Sn, Sb, Fe, and S. Teallite differs from franckeite by not containing Sb. Herein, naturally occurring sulfosalt materials, franckeite and teallite, undergo liquid-phase shear exfoliation, being examined for their structural and chemical properties. Subsequently, these exfoliated materials and their bulk counterparts are applied in electrocatalytic energy reactions. The results show the shear exfoliated teallite is the optimum sulfosalt for the oxygen evolution and reduction reactions. Finally, the shear-exfoliated franckeite shows improved hydrogen evolution performance in a wide pH range when compared to the remaining materials. This work demonstrates the promising potential of misfit-layered vdWH and layered sulfosalts as electrocatalysts for energy related applications.