Tuning oxygen reduction activity on chromia surface via alloying: a DFT study

Abstract

Economical electro-catalysts for the oxygen reduction reaction (ORR) are highly desirable for a range of advance energy storage technologies. Chromium compounds have been suggested as one possible source of non-precious metal based catalysts for oxygen reduction reaction (ORR), especially chromia (Cr 2 O 3) which is the most stable form of Cr oxide at room temperature. Using density functional theory + U calculations, we investigate the 4-electron ORR on the hydroxylated Cr 2 O 3 surfaces alloyed with 17 different transition metals. On the one hand, we find that the ORR overpotential is lower when the Cr 2 O 3 surface alloyed with elements towards the end of both the first and second rows of transition metals. Among these elements, Cd alloyed Cr 2 O 3 surface is found to promote the ORR the most, but due to its high toxicity and price it loses out to Zn as the recommended alloyant. On the other hand, we find that the ORR overpotential is generally higher and less varied on the Cr 2 O 3 surface alloyed with the early-to-mid row transition metal elements (e. g. Zr, Ti). As Cr 2 O 3 is also a major component in the passive film on stainless steels, where a low ORR rate is desirable to reduce the impact of localized corrosion. This implies that alloying with early-to-mid row transition elements could be beneficial to stainless steels. The difference in oxygen reduction activity is attributed to the tendency of forming stable ORR intermediates during the oxygen reduction process.

H2 Activation on Pristine and Substitutional ZnO(101̅0) and Cr2O3(001) Surfaces by Density Functional Theory Calculations

“…Cr 2 O 3 was widely studied in the field of molecular adsorption and reactions using DFT before, such as adsorption of carbon dioxide 38 and hydrogen sulfide, 39 catalytic oxidation of nitric oxide, 40 and the oxygen reduction reaction. 41 However, compared to ZnO, investigation of hydrogen activation on Cr 2 O 3 as well as the influence of heterometal atoms has not been reported yet. Finally, different from transition metals, at higher temperatures, the dissociated products might recombine to form H 2 or react with the lattice oxygen to form H 2 O with oxygen vacancies left.…”

“…It is therefore interesting to study the influence of heterometal atoms on activation of hydrogen molecules. Cr 2 O 3 was widely studied in the field of molecular adsorption and reactions using DFT before, such as adsorption of carbon dioxide and hydrogen sulfide, catalytic oxidation of nitric oxide, and the oxygen reduction reaction . However, compared to ZnO, investigation of hydrogen activation on Cr 2 O 3 as well as the influence of heterometal atoms has not been reported yet.…”

Revisiting Cl-Induced Degradation of MnS Inclusions Using DFT

“…For the oxide layer, the chloride attack can lead to the formation of oxygen vacancies. The oxygen vacancies can serve as reactive sites to promote the cathodic oxygen reduction reaction (ORR), , accelerating the anodic dissolution and hence the corrosion process.…”