Functionalized substrates are provided comprising a substrate and a plurality of transition metal dichalcogenide (TMD) heterostructures on a surface of the substrate, each TMD heterostructure comprising a TMD shell over a heterogeneous nucleation site, thereby providing a core-shell heterostructure, the heterogeneous nucleation site composed of a heterogeneous nucleation material; and a TMD wing extending outwardly from the core-shell heterostructure and non-parallel to and above the substrate surface. Electrocatalytic systems comprising the functionalized substrates are also provided.