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Horner, Oliver

University of British Columbia

Hydrogen production from seawater electrolysis has the potential to revolutionize the green energy industry. However, it suffers from a multitude of issues, such as the salts and compounds in seawater damaging the catalysts and electrolyzer components. In particular, corrosive hypochlorite formed at the anode during seawater electrolysis from the chloride oxidation reaction competes with the preferred oxygen evolution reaction. The methods used in the field to determine a catalyst's selectivity for forming hypochlorite or oxygen can yield erroneously high oxygen selectivity because of the decay of hypochlorite. The stability of hypochlorite was examined in the presence of metal ions of commonly used anode electrocatalysts in seawater electrolysis. The metal ions, in particular Ru³⁺ and Ni²⁺, catalyze the decomposition of hypochlorite. Elevated temperatures, e.g., 40 ℃, also cause hypochlorite to decay rapidly. The rotating ring-disc electrode technique was used to characterize IrO₂, NiO, Co₃O₄, RuO₂, Pt/C and PtRu electrocatalysts in situ at near-neutral pH with linear scanning voltammetry, potentiostatic and galvanostatic experiments. Increasing chloride concentration decreases the selectivity for oxygen production, and increasing temperature increases the selectivity for oxygen production. Bubbles formed during the formation of oxygen decrease the selectivity for oxygen production as hypochlorite formation preferentially occurs on the bare catalyst, and increasing chloride concentration decreases the selectivity for oxygen evolution reaction (OER). PtRu is discovered as a promising anode electrocatalyst for seawater electrolysis with excellent selectivity in the presence of chloride; increasing chloride concentration from 0.1 to 1 M caused a threefold increase in the OER current density on PtRu.

Text

2024-04-26

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/88036

Chemical and Biological Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/