Date of Graduation

5-2024

Document Type

Thesis

Degree Name

Master of Science in Materials Engineering (MS)

Degree Level

Graduate

Department

Materials Science & Engineering

Advisor/Mentor

Chen, Jingyi

Committee Member

Wang, Feng

Second Committee Member

Kilyanek, Stefan M.

Third Committee Member

Tung, Chao-Hung Steve

Fourth Committee Member

Leftwich, Matthew B.

Keywords

Electrocatalysis; Materials Science; Nanostructures; Synthesis

Abstract

Transition metal phosphides have become a new class of materials to be considered as promising catalysts for a number of applications including electrochemical hydrogen evolution (HER). Electrocatalysis in hydrogen evolution is a heavily studied field due to the increasing desire to develop more efficient and more cost-effective catalysts for clean hydrogen production. This project develops a chemical approach to synthesizing bimetallic cobalt-nickel phosphide nanostructures for their use in HER. The synthesis is accomplished by thermal decomposition of the metal precursors in the presence of carbon monoxide (CO) and trioctyl phosphine (TOP). The resulting nanostructures were characterized using transition electron microscopy for morphology, x-ray diffraction for composition, and inductively coupled plasma mass spectrometry for elemental concentration. The results show that bimetallic nanorods are formed, while the aspect ratio of the nanorods can be controlled by the CO injection temperature. Both CO and TOP are the key components for the formation of bimetallic nanorods, as well as the presence of both metal precursors. Additionally, a range of different nanostructures can be formed by varying the reaction conditions. These nanostructures are evaluated by linear sweep voltammetry in an alkaline electrolyte for HER. The results show that some of the phosphide nanostructures have potential to out-perform the common standard, Pt/C, at high current densities. Some correlations between the performance and composition/morphology of the nanostructures are analyzed and discussed. This study offers a solution-based chemical method for the shape-controlled synthesis of metal phosphide nanostructures that opens up the opportunities to tune their catalytic activity in various applications.

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