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Date Permissions Signed


Date of Award

Summer 2022

Document Type

Masters Thesis

Department or Program Affiliation


Degree Name

Master of Science (MS)



First Advisor

Bussell, Mark E.

Second Advisor

Emory, Steven R.

Third Advisor

Berger, Robert F.


Converting CO2 to CO via the photocatalyzed reverse water gas shift (RWGS) reaction satisfies a critical step in the production of C1 solar fuels (e.g., CH4, CH3OH) and longer hydrocarbons via the Fischer-Tropsch process. Oxide-supported nickel phosphides (NixPy) are an emerging class of photocatalysts with a number of accessible crystalline phases. Additionally, the broad-spectrum absorption of NixPy materials affords photo-induced local heating to drive catalytic processes at mild operating temperatures. In the current project, NixPy with different P/Ni molar ratios were investigated as RWGS catalysts on two types of support materials: 1) silica (SiO2) as a relatively inert support, and 2) a reducible oxide support (TiO2). NixPy/SiO2 catalysts (2.5 wt%) were synthesized via incipient wetness impregnation followed by temperature-programmed reduction (TPR); crystalline phases (Ni2P, Ni12P5, Ni3P) were identified using X-ray diffraction and compositions were determined by inductively coupled plasma optical emission spectroscopy (ICP-OES), and ongoing RWGS studies were carried out in a batch photoreactor using a Xe lamp (300 W) with the gas composition monitored by gas chromatography. Initial studies were executed using a SiO2 support, which is inactive for the RWGS reaction under light exposure, enabling the photocatalytic properties of the different NixPy phases to be probed. Trends of increasing CO selectivity and decreasing CO2 conversion have emerged as the P/Ni molar ratio increases, while the photo enhancement (light/dark activity ratio) decreases. Studies were then repeated for 2.5 wt% NixPy/TiO2 to evaluate the effect of a reducible oxide support and gain insight on the roles of the support and NixPy-support interface in determining the RWGS photocatalytic properties.




nickel phosphide, reducible oxide, RWGS, heterogeneous catalysis


Western Washington University

OCLC Number


Subject – LCSH

Phosphides--Synthesis; Water-gas--Reactivity; Cobalt compounds--Synthesis; Catalysts--Absorption and adsorption




masters theses




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Available for download on Thursday, August 10, 2023

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