Amonyak borandan metanoliz yöntemiyle hidrojen eldesi için siyah fosfor bazlı fotokatalizör tasarımı ve sentezi

In recent years, various two-dimensional (2D) materials have attracted great attention due to their unique electrical, thermal, and optical properties. Among them, 2D black phosphorus (BP), thermodynamically the most stable member of phosphorus allotropes, has received great attention in the fields of nanoelectronics, optoelectronics and catalysis owing to its advantageous properties such as having a tuneable optical bandgap and metal-devoid structure in addition to its visible light active characteristics with a high charge carrier mobility. However, there are some limitations that hinder the usage of BP in catalysis applications such as the difficulties in its synthesis and handling along with ambient instability. On the other hand, graphitic carbon nitride (g-CN), another emerging 2D semiconductor material, has attracted attention in catalysis because of its desirable properties such as being metal-free and low-cost but it holds certain drawbacks e.g. relatively large optical band gap and rapid recombination of charge carriers. Construction of heterojunctions between different semiconductors and/or metal nanoparticles (NPs) is a promising strategy to overcome the problems associated with the charge recombination and thus to create more efficient photocatalysts. In this thesis, we aimed to develop a novel heterojunction photocatalyst comprising g-CN and BP semiconductors and AgPd alloy NPs and test their catalytic performance in hydrogen generation from the methanolysis of ammonia borane (AB). To do so, bulk BP crystals were synthesized by using a vapor transport method and then exfoliated in a suitable solvent in order to combine it with mesoporous g-CN (mCN) and as-synthesized AgPd alloy NPs, yielding a ternary composite (mCN/BP/AgPd). The yielded ternary nanocomposite was shown to have a suitable heterojunction between semiconductor BP and mCN with appropriate band gap energies and band positions, which greatly contributes to increased photocatalytic activity of AgPd alloy NPs in the methanolysis of AB. The structure of mCN/BP/AgPd nanocomposites was characterized by using advanced analytical tools. Next, they were employed as catalysts in hydrogen generation from the methanolysis of AB under ambient conditions. Different parameters including mCN/BP ratio in the binary nanocomposite, AgPd alloy nanoparticles composition, surface stripping procedures, and light-source were investigated with detailed kinetic studies to find the optimum conditions to boost the photoactivity of mCN/BP/AgPd ternary nanocomposites in the methanolysis of AB. The highest photocatalytic activity with an turnover frequency (TOF) value of 43.7 mol H2 mol AgPd−1 min−1 was achieved by using g-CN/BP ratio of 5/1, applying an acetic acid treatment (AT), and Ag1Pd1 alloy composition under blue LED irradiation at room temperature. The reusability of the optimized mCN/BP/AgPd/AT ternary nanocomposites was shown with a five-cycle photocatalytic test, with the photocatalyst retaining 70% of its initial activity at the last cycle.