Chromium Single-Atom Catalyst with Graphyne Support: A Theoretical Study of NO Oxidation and Reduction

Abstract

Catalytic mechanisms and bonding analysis of NO oxidation and reduction on Cr single-atom catalysts (SAC) dispersed on the graphyne (GY) surface have been systematically investigated using the first-principles theoretical methods. GY is a decent support for isolated transition-metal (TM) atom catalysts because the most active sp-hybridized carbon atoms exist on the GY surface. All the single TM atoms are trapped into the void of the GY surface and existed in the isolated form. The molecular geometries and adsorbate binding energies of NO@TM–GY, ON@TM–GY, and O2@TM–GY configurations are determined. We find that the Cr–GY is the most promising SAC for NO oxidation and reduction compared with the other TM-SACs. Herein, we report an efficient NO oxidation and reduction catalyzed by Cr–GY at ambient temperature. We find that Cr–GY SAC is very reactive for NO oxidation and reduction at ambient temperatures with low activation barriers to the rate-determining steps for Eley–Rideal (0.87, 0.60, and 0.62 eV) and Langmuir–Hinshelwood (0.69, 0.62, and 0.84 eV) mechanisms. The Termolecular Eley–Rideal mechanism for the formation of the NO2 molecule is not thermodynamically favorable. Comparative analysis revealed that the NO reduction (0.62 eV) is more favorable than NO oxidation (0.84 eV). These findings provide valuable perceptions for design of highly efficient and selective heterogeneous SACs for NO oxidation and reduction with TMs.

Research Progress and Application of Single-Atom Catalysts: A Review

“…However, due to the high cost of NH 3 reduction, the development of economical and green catalysts is the key. Through first-principles calculations, Li et al [78] found that the Cr single-atom catalyst supported on graphene is the most promising single-atom catalyst for NO oxidation. Compared with precious metals, the 3D orbitals of transition metals Fe and Co do not form paired electrons, so they have unique activities [79].…”

Theoretical Inspection of M1/PMA Single-Atom Electrocatalyst: Ultra-High Performance for Water Splitting (HER/OER) and Oxygen Reduction Reactions (OER)

“…A large number of SACs were used individually during diverse chemical reactions. However, an increase in the surface free energy with a decrease in metal particle size results in the formation of metal clusters. , Thus, substantial efforts for SACs have been made to develop a practical support that can efficiently anchor the single-metal atom and avoid metal cluster formation without a decrease in the support performance. − Recently, Li et al reported that a Cr adatom on the 2D material graphyne (GY) is thermodynamically stable and has superb catalytic activity for NO oxidation and reduction reactions, with rate-determining steps of 0.84 and 0.62 eV, respectively . Numerous single-transition-metal (TM) atoms embedded on different supports, such as metal oxides, , metal–organic frameworks, , graphene, , g-C 3 N 4 , and MXene, − have been investigated both experimentally and computationally for their catalytic performance.…”

A polyoxometalate cluster-based single-atom catalyst for NH3 synthesis via an enzymatic mechanism

“…45 Recently, Talib et al reported that a single Cr atom embedded over a graphyne Cr 1 /GY surface is an efficient catalyst for the NO oxidation and reduction reaction under normal reaction conditions. 46 Prior investigation proved that SACs exhibit massive potential in many catalytic reactions, such as CO oxidation, CO 2 reduction reaction (CO 2 RR), oxygen evolution/reduction (OER/ORR), NO oxidation, and reduction reaction. For this reason, SACs arouse significant curiosity in N 2 fixation and catalytic conversion of N 2 into NH 3 .…”