Abstract

This doctoral thesis is devoted to the synthesis and investigation of ammonium/potassium vanadates, which constitute an interesting group of materials due to their potential applications in electrochemical devices and photocatalysis. The scope of the conducted experimental work included the synthesis of ammonium/potassium vanadates, their physicochemical characterization using various methods (spectroscopy, microscopy, thermal analysis and others), and evaluation of their use as cathode materials for Lithium-ion batteries (LIBs) or photocatalysts for the degradation of water contaminants. The main part of the thesis presents the conducted research and its analysis and consists of a collection of five articles [A1-A5] published in the following journals: Electrochimica Acta (IF 6.901, 100 pts. MEiN, 2020), Inorganic Chemistry (IF 5.436, 140 pts. MEiN, 2022), Materials (IF 3.057, 140 pts. MEiN, 2019), and Scientific Reports (IF 4.996, 140 pts MEiN, 2022 and 2023). This part is preceded by a brief introduction to the vanadate family, general motivation for the conducted research, and the current state of knowledge about ammonium/potassium vanadates, with special regard to their application as electrode materials for metal-ion batteries and photocatalysts. In the final section, the most significant achievements obtained within this thesis are summarized, and future research directions are presented. As part of the research, repeatable synthetic routes for uniform nanostructures of ammonium/potassium vanadates were developed. Notably, for the first time, the effect of precursor morphology and initial pressure on the hydrothermal synthesis of ammonium vanadates was studied. Furthermore, it has been proven that the obtained ammonium/potassium vanadates can be successfully used as efficient cathode materials for LIBs and as solar light-driven photocatalysts for decomposing water pollutants. In the case of the former application, hydrated vanadate compounds, i.e., (NH4)2V10O25∙nH2O and K2V6O16·nH2O were tested and described for the first time. For the latter, two new photocatalytic materials were proposed (KV3O8 and a composite based on NH4V4O10 and reduced graphene oxide). In addition, more detailed studies (kinetics and mechanism of the photocatalysis process) were presented for K2V6O16·nH2O and NH4V4O10.

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