The impact of nitrogen oxides on electrochemical carbon dioxide reduction

Abstract

The electroreduction of carbon dioxide offers a promising avenue to produce valuable fuels and chemicals using greenhouse gas carbon dioxide as the carbon feedstock. Because industrial carbon dioxide point sources often contain numerous contaminants, such as nitrogen oxides, understanding the potential impact of contaminants on carbon dioxide electrolysis is crucial for practical applications. Herein, we investigate the impact of various nitrogen oxides, including nitric oxide, nitrogen dioxide, and nitrous oxide, on carbon dioxide electroreduction on three model electrocatalysts (i.e., copper, silver, and tin). We demonstrate that the presence of nitrogen oxides (up to 0.83%) in the carbon dioxide feed leads to a considerable Faradaic efficiency loss in carbon dioxide electroreduction, which is caused by the preferential electroreduction of nitrogen oxides over carbon dioxide. The primary products of nitrogen oxides electroreduction include nitrous oxide, nitrogen, hydroxylamine, and ammonia. Despite the loss in Faradaic efficiency, the electrocatalysts exhibit similar carbon dioxide reduction performances once a pure carbon dioxide feed is restored, indicating a negligible long-term impact of nitrogen oxides on the catalytic properties of the model catalysts.

Impact of Alkali Cation Identity on the Conversion of HCO3− to CO in Bicarbonate Electrolyzers

“…[10] Moreover, the feedstock must be free of impurities (e. g., NO x , O 2 ) that reduce the efficiency of the electrolyzer. [11,12] These issues with upstream CO 2 capture drive up the capital and operating costs of gas-fed CO2RR electrolyzers. [13][14][15] These challenges with gaseous feedstocks prompted us to design bicarbonate electrolyzers that directly convert aqueous carbon capture solutions (e. g., KHCO 3(aq) ) into CO while also producing OH À to regenerate the carbon capture sorbent (Figure S2).…”

Advances in Electrochemical Ammonia Synthesis Beyond the Use of Nitrogen Gas as a Source

“…[40,41] Similarly, NO x redox potentials are more positive than those of CO 2 , indicating that it is thermodynamically more favorable to reduce NO x than CO 2 . A nice work published recently discussed the NO x impurities in CO 2 stream that caused significant Faradaic efficiency (FE) loss in CO 2 reduction reaction, [42] which suggested the much better kinetics of NO x electroreduction than CO 2 RR. In the following sections, we will discuss recent studies of electrochemical NO x reduction on heterogeneous catalyst surfaces in terms of cathode materials, applied cathodic potential, and electrolytes, aiming to understand fundamentally the structure-activity relationship and the factors that govern the product selectivity.…”

Gas evolution in electrochemical flow cell reactors induces resistance gradients with consequences for the positioning of the reference electrode

“…By introducing an empirical pair of current density j e and specic resistance r e , which are discussed further in Section 3.2, j 0 can, based on eqn (12), be determined as: If this expression is inserted back into eqn (12) and solved for r(x) (see ESI † for details), the following expression results: r CT ðxÞ ¼ ln jðxÞ j e ðbjðxÞÞ À1 þ j e jðxÞ r e (14) Note that eqn (14) does not rely on j 0 and U 0 anymore. This is of an advantage, as these entities can hardly be estimated.…”

“…9 As the operation of gas diffusion electrodes is challenging, they are commonly only applied at the cathode side of a CO 2 RR ow cell. [10][11][12] At the anode side, the oxygen evolution reaction usually occurs at a solid electrode in contact with the electrolyte. As water from the electrolyte is used as the reactant for oxygen evolution, a solid electrode can reach sufficient current densities.…”