Trends in the Adsorption of Oxygen and Li₂O₂ on Transition-Metal Carbide Surfaces: A Theoretical Study

Abstract

In this work we performed fundamental investigations of the adsorption of O 2 and Li 2 O 2 molecules on seven transition-metal carbide (TMC) surfaces, which present 3d, 4d and 5d TM, where TM = Ti, V, Zr, Nb, Mo, Hf and Ta. We employed density functional theory (DFT) with the semilocal meta-GGA SCAN functional. The oxide layer behaves as a passivation layer on the TiC(111), ZrC(111) and MoC(001) systems upon Li 2 O 2 adsorption, but promotes the formation of the Li 1 O 3 TM 1 layer on the VC(111), NbC(111), MoC(111), and HfC(111) surfaces due to the change in stoichiometry which is caused by the rst adsorbed Li 2 O 2 molecule. We showed that with increasing the number of the Li 2 O 2 molecules on the TMC surfaces, the contribution of the TMC surface states turns out less important to the adsorption energy of the molecules. After the rst layer of Li 2 O 2 it approaches the native crystal values, which occurs faster with the occupation of the TM d-bands. This work can make a contribution in fundamental understanding and development of new, TMC-based, catalysts for alkali-metal batteries.

Improved Durability of Ti3C2Tz at Potentials above the Reversible Hydrogen Electrode by Tantalum Substitution

“…Several possible oxygen binding positions were considered, this discussion is found in the supporting information. The adsorption energy of the O atom on the pristine and Ta-doped Ti 3 C 2 was observed to be −6.00 eV and −5.40 eV, respectively; this is close to the calculated adsorption energy, of O 2 on the FCC phase of TiC (111) surface, which was found to be −5 eV by Tereshchuk et al [36] We note in passing that the DFT calculations do not capture the influence of the MXene termination groups (T z ), which likely convolute the OBE calculation.…”

Nanoparticle Size Effects on Phase Stability for Molybdenum and Tungsten Carbides

“…The two Mo 2 C phases are α-Mo 2 C and β-Mo 2 C, and have Mo bonded to three C, each C to six Mo, and both have similar computed Bader charges with respect to Mo and C. We used DFT calculations with the PBE functional to optimize cell shape and atomic positions and compute the bulk formation energy for each structure; additional details of the calculations are reported in Section . For comparison, we used the strongly constrained and appropriately normed (SCAN) functional for all bulk structures of Mo x C y (Figure S3); consistent with recent reports, , we found that relative energies for PBE and SCAN were in close agreement. Optimized structural parameters of different Mo x C y phases, including cell parameters, space groups, and bulk energies, are listed in Table .…”

Li2O2 Formation Electrochemistry and Its Influence on Oxygen Reduction/Evolution Reaction Kinetics in Aprotic Li–O2 Batteries

“…A number of studies have shown that the electronic structure and surface properties of the cathode material play an important role in affecting the structure and morphology of the discharge product. [ 59,81–84 ] Nazar et al. discovered long time ago that sodium defects and vacancies in the acid‐leached Na 0.44 MnO 2 electrode had influence on the Li 2 O 2 formation electrochemistry.…”