Carbonaceous materials are not suitable catalysts for direct NO decomposition in exhaust aftertreatment

Abstract

New approaches for direct NO decomposition catalysis are urgently needed, but using carbonaceous supports appears not to be the way to go.

Computational insight into effective decomposition of NOX gas pollutants using N-vacancies in graphitic carbon nitride

“…17 These data well explain the low catalytic activity of pristine g-CN in the experimental work. 16 By contrast, when there exists an N 2C vacancy in the substrate, chemical bonding between NO/NO 2 and g-CN NV (Fig. 2c and d) can be formed, as supported by the shorter distance of 1.51/1.64 Å between the N of NO/NO 2 and the substrate C1 atom near the N 2C , stronger adsorption energies of −2.05/−2.28 eV, and significant electron transfer of −0.12/−0.31 |e| from g-CN NV to NO/NO 2 .…”

“…14 Since the graphitic carbon nitride (g-CN) material contains N, it was also adopted to study the NO X removal. 4,[16][17][18][19][20][21] However, direct NO decomposition into N 2 and O 2 on pure g-CN was not observed until the temperature was raised to 450 °C with a low conversion efficiency of 0.6% and 550 °C with a conversion efficiency of 8.9%. 16 Higher temperatures of over 700 °C are expected to effectively decompose NO, but such temperatures are not suitable for the stable existence of g-CN.…”

“…4,[16][17][18][19][20][21] However, direct NO decomposition into N 2 and O 2 on pure g-CN was not observed until the temperature was raised to 450 °C with a low conversion efficiency of 0.6% and 550 °C with a conversion efficiency of 8.9%. 16 Higher temperatures of over 700 °C are expected to effectively decompose NO, but such temperatures are not suitable for the stable existence of g-CN. Computationally, the NO X is demonstrated to be merely physisorbed on pristine g-CN and a large activation energy (3.62 eV) is required for NO decomposition into N and O radicals on g-CN.…”

“…By far, there is still a lack of direct experimental evidence that NO is indeed decomposed into products of N 2 and O 2 , 16 which indicates that the mechanism of NO X decomposition has not been sufficiently studied. Computational studies based on density functional theory (DFT) can be an ideal approach to provide a molecular-level understanding and demonstrate the chemical reaction mechanism according to experimental observation.…”

Achieving Digital Catalysis: Strategies for Data Acquisition, Storage and Use

“…Therefore, catalyst data accessible today, are generally not diverse enough. Particularly poor catalysts, which are often not mentioned in publications are, however, of great importance for data sets that are evaluated using machine learning [58b, 59] . Often as well, for a given reaction, the entire community focuses on only one or a few different catalyst compositions.…”