Atomic Layer Deposition of MoSe₂ Nanosheets on TiO₂ Nanotube Arrays for Photocatalytic Dye Degradation and Electrocatalytic Hydrogen Evolution

Herein, a hierarchical MoSe2/1D TiO2 nanotube layer structure was successfully fabricated in a simple and fast fashion and its photocatalytic and electrocatalytic properties were assessed. The novelty of this work lies in the utilization of the atomic layer deposition (ALD) technique to deposit MoSe2 nanosheets on 1D TiO2 nanotube layers. The photoelectrochemical and photo- and electrocatalytic properties were explored and optimized as a function of MoSe2 ALD cycles. ALD allowed precise control on MoSe2 nanosheet size, and in turn, on the surface structure, which is pivotal for efficient catalysts. The MoSe2 nanosheets grew on both the inner and outer 1D TiO2 nanotube surface mainly in a perpendicular orientation, maximizing the exposed active edges, an essential aspect to fully exploit the MoSe2 photo- and electrochemical properties. Outstanding photo- and electrocatalytic activities were recorded in both organic dye pollutant degradation and hydrogen evolution reaction applications, respectively. The excellent photocatalytic and electrochemical activities stem from the synergy between tailored ALD loading of MoSe2 nanosheets and the 1D TiO2 nanotubular structure with a high surface/volume ratio, which provides fast electron transfer and easy access to the MoSe2 active edges, boosting the catalytic activity.