Ni-Doping Effects on Oxygen Removal from an Orthorhombic Mo₂C (001) Surface: A Density Functional Theory Study

Abstract

Density functional theory (DFT) calculations were used to investigate the effect of Ni dopants on the removal of chemisorbed oxygen (O*) from the Mo-terminated (T Mo ) and C-terminated (T C ) Mo 2 C(001) surfaces. The removal of adsorbed oxygen from the catalytic site is essential to maintain the long-term activity and selectivity of the carbide catalysts in the deoxygenation process related to bio-oil stabilization and upgrading. In this contribution, the computed reaction energetics and reaction barriers of O* removal were compared among undoped and Ni-doped Mo 2 C(001) surfaces. The DFT calculations indicate that selected Ni-doped surfaces such as Ni adsorbed on T Mo and T C Mo 2 C(001) surfaces enable weaker binding of important reactive intermediates (O*, OH*) compared to the undoped counterparts, which is beneficial for the O* removal from the catalyst surface. This study thus confirms the promoting effect of the Ni dopant on O* removal reaction on the T Mo Mo 2 C(001) and T C Mo 2 C(001) surfaces. This computational prediction has been confirmed by the temperature-programmed reduction profiles of Mo 2 C and Ni-doped Mo 2 C catalysts, which had been passivated and stored in an oxygen environment.

Non‐3d Metal Modulation of a 2D Ni–Co Heterostructure Array as Multifunctional Electrocatalyst for Portable Overall Water Splitting

“…Previous studies have demonstrated that the modification of electrocatalysts on molecular level can greatly enhance the thermodynamics and/or kinetics of electrocatalytic reactions, which can be achieved through rational designed synthetic process, such as constructing heterostructures, and transition‐metal doping . For example, V, Fe, Co, Ni, and Zn have been applied as dopants to modify the energy levels of catalysts, and improved their electrocatalytic activities. Recently, non‐3d high‐valence metals, such as Mo and W, were proved to be ideal dopants due to their unique advantages in optimizing Gibbs free energy (Δ G ) of formation of electrocatalytic intermediates, e.g., Δ G H* for HER and Δ G OH* for OER,7b,15 which paves a new path to boost performance of electrocatalyst.…”

Surface and Interface Engineering: Molybdenum Carbide–Based Nanomaterials for Electrochemical Energy Conversion

“…can improve the catalytic performance by modulating the electronic configuration, producing new active sites and activating the surrounding sites. [ 88 ] Zhou et al [ 79 ] have investigated the role of “Ni” dopant atom toward the oxygen removal from the Mo 2 C (0 0 1) catalyst surface. The Bader charge analysis results showed that the charges values of Ni are −0.31 ( Figure ) and −0.16 (Figure 4b), corresponding the Ni‐adsorbed and Ni‐replaced on the Mo‐terminated Mo 2 C (0 0 1) surface, respectively.…”

“…Reproduced with permission. [ 79 ] Copyright 2018, American Chemical Society. e) SEM, f) TEM, and g) HR‐TEM images of Co‐Mo 2 C‐0.020 and h) their STEM images and the corresponding elemental mappings.…”

“…Heteroatom doping into materials lattice can tune the electronic or surface structures of the material and in turn influence the adsorption free energy of reaction intermediates on the surface for boosting the catalytic efficiency. [74,78,79] Heteroatom modification demonstrates that the additional heteroatoms replace the crystal lattice sites of material. The enhanced catalytic performance would be contributed to the optimized electronic configuration, which induced by the additional heteroatom element affecting the coordination environments of the surrounded elements in the composite.…”

“…[100] Heterostructures, as a promising strategy for highly efficient electrochemical energy conversion, have been successfully applied in Mo x C-based catalytic materials, such as Reproduced with permission. [79] Copyright 2018, American Chemical Society. e) SEM, f) TEM, and g) HR-TEM images of Co-Mo 2 C-0.020 and h) their STEM images and the corresponding elemental mappings.…”