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Surface Modifications of Ti 2 CO 2 for Obtaining High Hydrogen Evolution Reaction Activity and Conductivity: A Computational Approach
Author(s) -
Wang Shuo,
Chen Liang,
Wu Yang,
Zhang Qiuju
Publication year - 2018
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201800899
Subject(s) - conductivity , doping , mxenes , hydrogen , fermi level , vacancy defect , band gap , materials science , activation energy , chemistry , analytical chemistry (journal) , crystallography , nanotechnology , electron , physics , optoelectronics , organic chemistry , chromatography , quantum mechanics
The identification of hydrogen evolution reaction (HER) catalysts with high conductivity and high activity is the top priority in the development of renewable energy. Oxygen‐terminated Ti 2 C (Ti 2 CO 2 ), as one of the typical MXenes, shows good HER Gibbs free energy (Δ G H ) at low hydrogen coverage, whereas the large band gap of approximately 1.0 eV limits its conductivity capability. By doping phosphor (P) or sulfur (S) to partially substitute the surficial O, the average free energy (Δ G H a ) at various hydrogen coverages has been draggd to approach zero, and the conductivity is also significantly improved by narrowing the band gap to lower than 0.3 eV. Partial charge analysis indicates that doping P or S on the surface induces the diffusion of electrons on oxygen from O 2p x to O 2p z , resulting in O 2p z reaction with H 1s. The facial overlapping of H 1s with O 2p z will strengthen the binding strength, hence lowering Δ G H . The energy shift toward Fermi level of Ti 3d after P or S doping contributes to the reduced band gap and high conductivity. Surficial O or P vacancies are created to evaluate the vacancy effect on HER performance, which not only improves Δ G H a and conductivity but also leads to a low reaction barrier of H 2 O splitting (<0.2 eV). The armchair nanoribbon (ANR) displays improved HER activity by P‐doping at 50% ratio. Our research shows that modification of end‐group in MXenes can effectively improve HER catalytic activity and conductivity, which is expected to promote their potential applications in electrocatalysis and energy conversion.