Transition metal dichalcogenides: nanostructuring strategies and engineering for water electrolysis

Escalera López, Daniel ORCID: 0000-0002-2001-9775 (2019). Transition metal dichalcogenides: nanostructuring strategies and engineering for water electrolysis. University of Birmingham. Ph.D.

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Abstract

Transition metal dichalcogenides (TMDs) are a family of ubiquitous and inexpensive inorganic layered materials, with an ever-growing set of physicochemical properties. Namely, the edge site confined hydrogen evolution reaction (HER) electrocatalysis found in pristine TMDs is of high interest to replace the scarce precious metals currently employed in proton exchange membrane electrolysers. The core of this thesis is devoted to the maximization of the electrocatalytic activity of TMDs, here being MoS2 and WS2, towards the HER in acidic electrolytes by use of physical and electrochemical techniques. Activation of the electrochemically inert sulfur edge sites in MoS2 was undertaken by preparation of Ni-MoS2 hybrid nanoclusters using a dual-target magnetron sputtering and gas condensation technique. The HER enhancement observed is limited by the sulfur-deficient inherent nature of the size-selected MoS2 nanoclusters, which hampers their crystallinity and electrochemical stability, amended here by a post-sulfidation treatment consisting of sulfur evaporation and annealing. Edge site exposure is alternatively explored for crystalline TMD flakes by fabrication of nanopillar/nanocone array structures, investigating their morphology-dependent mass transport properties and chalcogen-dependent HER catalysis. Insight on the pH-dependent HER activity and stability of electrodeposited amorphous molybdenum sulfide is thoroughly investigated, proposing the moieties responsible for the observed HER catalysis. Lastly, the potential of tungsten sulfide decoration to mitigate iridium corrosion under acidic oxygen evolution reaction conditions is evaluated.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):