On Molybdenum Sulfides and Other Active Materials for Sustainable Energy Systems

Abstract

To respond to the approaching climate crisis, the current energy landscape must shift towards sustainable, decarbonised systems. This shift will require the development of inexpensive and active energy conversion materials. The work within this thesis reports the investigation of several candidate materials, i.e. molybdenum sulfides and carbides, for use as catalysts and electrodes in energy conversion processes. These materials were chosen for their natural abundance, controllable morphologies, and varied chemistries. Chapter 1 focuses on the scope and potential of Chevrel phases (MxMo6S8) as catalytic materials. It includes both a critical literature review and original research on nanoparticulate catalysts that exhibited excellent performance for the hydrogen evolution reaction. Chapter 2 focuses on the various morphologies of MoS2 and incorporates two reviews: the first review summarises all known reports of 3R-MoS2 and clarifies inconsistencies with the literature. The second review rectifies the errors in the literature on hydrothermally produced 1T-MoS2 and provides best practice analysis instructions. The final section of Chapter 2 is an investigation into the effect of crystal disorder on the electrochemical performance of MoS2 in hybrid batteries in order to aid the optimisation of MoS2 electrodes. Chapter 3 is comprised of a study that elucidates the structure of a highly active lignin valorisation catalyst, Mo2CxNx-1/TiN. The analyses show that the titanium nitride and molybdenum carbide phases are intimately mixed and that the catalyst incorporates terminal Mo≡N motifs. Chapter 4 includes studies on the silver catalysed reduction of 4-nitrophenol; a ubiquitous model reaction. A detailed kinetic analysis of the reaction mechanism elucidates the role of oxygen during the induction period of the reaction. The research-level chemistry and protocols were then adapted to be used as a pedagogical tool.