Real-Time Growth Study of Binary and Ternary Nickel-Antimony-Arsenic Nanocrystals using ETEM

Sammanfattning

Transition metal-pnictides are a select field of crystalline materials which allows property modification of common d-block metals through alloying with pnictides. Among them, Nickel-based pnictides have been gaining attention due to their earth abundance and low cost. Ni-As and Ni-Sb have both demonstrated the use as catalyst materials for the hydrogen- and oxygen evolution reactions where controlled synthesis of ternary Ni-Sb-As phases could realise new design possibilities of novel catalyst materials. However, only a very small number of nanoscale phases have been reported with limited insights on the growth processes. In this thesis, we utilized environmental transmission electron microscopy to examine nucleation behaviour, growth propagation and phase transformations in situ of binary Ni-As and Ni-Sb as well as ternary Ni-Sb-As nanocrystals. In the first part of this thesis, we investigated growth dynamics of the binary systems, Ni-As and Ni-Sb, where the synthesis parameters were also optimised with regards to achieving homogeneous nanoparticles with high phase selectivity. In the second part of this thesis, we considered three growth strategies to synthesise ternary phase nanoparticles based on the optimised parameters from the first part. The three growth strategies were also evaluated based on uniformity of the nanoparticles and phase selectivity. The experiments resulted in successful synthesis of novel binary and ternary nanomaterials which had not been found in the reviewed literature. Further fine tuning of the synthesis parameters could realise greater control over the final crystal structure and chemical composition. These results provide valuable insights for a novel synthesis method of 0D nanomaterials which can be applied for future manufacturing of advanced catalyst materials.