Metal sulfide nanomaterials for photocatalytic water splitting: growth control in water/ionic liquids and early-stage strategies against photocorrosion Tannith-Jade Cole and Graeme Hogarth Department of Chemistry, King's College London, Britannia House, 7 Trinity Street, London, SE1 1DB Metal sulfide nanomaterials have shown themselves to be versatile photocatalysts with tunable bandgaps and properties which benefit many areas of chemistry. There has been significant interest in metal sulfides as catalysts for photocatalytic water splitting, with MoS 2 being a particularly effective catalyst for the hydrogen evolution reaction (HER) 1 . Nickel, zinc and cobalt sulfides, and their nanocomposites, have also shown interesting HER activity, which is highly dependent on the nanoparticle phase, morphology and surface chemistry. 2,3 There is significant room to improve the performance of these materials in photocatalytic water splitting, however controlling nanoparticle properties without hindering catalytic activity is a synthesis challenge addressed in this work. A particularly good method for controlling nanoparticle growth is the heat-up/hot-injection method which uses high-boiling solvents as surfactants, such as oleylamine. These methods allow significant phase and morphology control, however, the solvent binds strongly to the nanoparticle surface and can be a challenge to remove. As a result, the active sites on the nanoparticle surface are blocked, hindering photocatalysis. This work presents two effective heat-up/hot-injection synthesis methods for the controlled growth of “bare” metal sulfide nanoparticles, with a focus on developing metal sulfide catalysts for photocatalytic water splitting. 1) A scalable low temperature heat-up method in water using metal dithiocarbamate precursors. This method generates “bare” nanoparticles due to the weak interaction between the soft metal sulfide surface and water. 4 These nanoparticles can be functionalised with carefully designed functional ligands after synthesis. 2) The controlled synthesis of metal sulfide nanoparticles in ionic liquids by careful tuning of solvent properties. A secondary aim for the use of ionic liquids as a growth medium is their potential to enhance photocatalytic performance and stability - a topic which will be explored in this poster. The metal sulfides presented in this work are nickel and zinc sulfides and ternary metal sulfides with nickel, molybdenum and cobalt sulfides. The long-term goal of this work is not only to synthesise metal sulfides in new ways for applications in photocatalytic water splitting, but to stabilise them, particularly zinc sulfide, against photocorrosion with carefully designed capping-groups/ionic liquids/deep eutectic solvents without the need for precious metals and co-catalysts. References 1. Alfa, H. Y. Hafeez, J. Mohammed, S. Abdu, A. B. Suleiman and C. E. Ndikilar, Int. J. Hydrogen Energy , 2024, 71 , 1006. 2. V. V. N. R. Rao, K. P. Devi, P. S. R. Rao and S. K. Singh, Int. J. Hydrogen Energy , 2023, 48 , 20389–20409. 3. Lange, S. Reichenberger, S. Ristig, M. Rohe, J. Strunk, S. Barcikowski and R. Schlögl, Prog. Mater. Sci. , 2022, 124 , 100865. 4. Bergstrom Mann, I. J. McGregor, S. Bourke, M. Burkitt-Gray, S. Fairclough, M. T. Ma, G. Hogarth, M. Thanou, N. Long and M. Green, Nanoscale Adv. , 2019, 1 , 522–526.
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