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Date Permissions Signed

8-2-2022

Date of Award

Summer 2022

Document Type

Masters Thesis

Department or Program Affiliation

Chemistry

Degree Name

Master of Science (MS)

Department

Chemistry

First Advisor

Bussell, Mark E.

Second Advisor

Emory, Steven R.

Third Advisor

Berger, Robert F.

Abstract

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.

Type

Text

Keywords

nickel phosphide, reducible oxide, RWGS, heterogeneous catalysis

Publisher

Western Washington University

OCLC Number

1340459865

Subject – LCSH

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

Format

application/pdf

Genre/Form

masters theses

Language

English

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.

Rights Statement

http://rightsstatements.org/vocab/InC-EDU/1.0/

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