2D MoTe2 nanosheets by atomic layer deposition: Excellent photo- electrocatalytic properties

•Newly Tellurium compound introduced as suitable Te ALD precursor.•Successful ALD of MoTe2 nanostructures on various substrates demonstrated.•2D flaky MoTe2 nanosheets randomly oriented maximizing exposure of active sites.•Remarkable catalytic properties including HER electrochemical activation.•Presented results pave the way for ALD deposition of MoTe2 for various applications. Herein, the synthesis of MoTe2 nanosheets by means of Atomic Layer Deposition (ALD) is demonstrated for the first time. ALD enables tight control over the thickness and the composition of the deposited material, which are highly appealing features for the nanostructure fabrication. The growth of ALD MoTe2 was studied on substrates of different nature, including TiO2 nanotube (TNT) layers used as active supporting material for fabricating hierarchical nanotubular MoTe2/TNT heterostructure. The combination of newly synthesized Te precursor with commercial Mo precursor rendered the growth of 2D flaky MoTe2 nanosheets mostly out-of-plane oriented. The as-deposited MoTe2 was extensively characterized by different techniques which confirmed its chemical composition and revealed 2D flaky nano-crystalline structures. In parallel, MoTe2/TNT layers were employed to explore and exploit both photo- and electrocatalytic properties. The synergy stemming from the out-of-plane MoTe2 nanosheet orientation, with an optimized amount of catalytic active edges, and the fast electron transfer through 1D TiO2 nanotubes triggered the catalytic properties for both, organic pollutant degradation and hydrogen evolution reaction (HER) applications. Remarkably, the application of a cathodic potential originated a gradual HER electrochemical activation over time driving to a higher current density and an overpotential drop. [Display omitted]