Functionalization of 2D materials for enhancing OER/ORR catalytic activity in Li–oxygen batteries

Abstract

A major barrier toward the practical application of lithium-oxygen batteries is the high overpotential caused by the precipitation of oxygen-reduction products at the cathode, resulting in poor cyclability. By combining first-principle calculations and reactive molecular dynamics simulations, we show that surface functionalization of 2D MXene nanosheets offers a high degree of tunability of the catalytic activity for oxygen-reduction and oxygenevolution reactions (ORR/OER). We show that the controlled creation of active vacancy sites on the MXene surface enhances ORR in excess of a factor of 60 compared to graphenebased cathode materials. Furthermore, we find that increasing the ratio of fluorine vs. oxygen termination of the functionalized Ti 4 N 3 -MXene catalyst reduces the charge overpotential by up to 70% and 80% compared with commercial platinum-on-carbon and graphene catalysts, respectively. These results provide direct guidance toward the rational design of functionalized 2D materials for modulating the catalytic activity for a wide range of electrocatalytic applications. 1 1234567890():,; ResultsAb initio thermodynamic analysis of charge and discharge processes at low overpotential. In order to examine the ARTICLE COMMUNICATIONS CHEMISTRY | https://doi.

Highly Efficient Nb2C MXene Cathode Catalyst with Uniform O‐Terminated Surface for Lithium–Oxygen Batteries

“…To further investigate the stability of various discharge products during cathode reaction and the influence on the electrode potential, we established a phase diagram of possible intermediates and discharge products in Figure 8a, showing the possible change of adsorbing species during the discharge process on Nb 2 CO 2 surface. [ 37,65,66 ] The formation of Li 2 O 2 through a two‐electron step is thermodynamically advantageous above 1.51 V. The formation voltage window of LiO 2 through the single‐electron step is 2.58–2.82 V. It worth noting that LiO 2 and Li 2 O 2 can spontaneously nucleate between the voltage window 2.58–2.70 V due to their similar free energy. When the voltage drops to 2.58 V, the nucleation of Li 2 O 2 begins to be the primary step.…”

“…It is thermodynamically feasible to adsorb LiO 2 (E ad = −0.60 eV) and then perform a surface. [37,65,66] The formation of Li 2 O 2 through a two-electron step is thermodynamically advantageous above 1.51 V. The formation voltage window of LiO 2 through the single-electron step is 2.58-2.82 V. It worth noting that LiO 2 and Li 2 O 2 can spontaneously nucleate between the voltage window 2.58-2.70 V due to their similar free energy. When the voltage drops to 2.58 V, the nucleation of Li 2 O 2 begins to be the primary step.…”

“…During the synthesis process, functional groups, such as O, F, and OH will be anchored on the surface of Nb 2 C MXene. It has been demonstrated theoretically that the surface O, F, and OH functional groups formed during the synthesis process will significantly influence the catalytic capability of Ti x C x−1 , [38,39,60] Ti x N x−1 [37] for LOBs. In the present work, the catalytic capability of the four type surface structures decorated by O, F, OH functional groups and bare Nb 2 C were first characterized.…”

State-of-the-art surface oxide semiconductors of liquid metals: an emerging platform for development of multifunctional two-dimensional materials

“…Surface functionalization approaches offer a unique platform for synthesis of advanced functional 2D materials for a wide range of electronic applications. [170][171][172][173][174] The 2D surface oxide of liquid metals as one of the natural sources of 2D materials can also be functionalized via sonochemical- assisted reactions to nally synthesize ultra-thin functionalized Ga 2 O 3 nanosheets with controllable electronic and optoelectronic properties. For example, in a recently developed technique, the sonochemical assisted functionalization of liquid metal nanoparticles with selenium and silver nanostructures led to a tangible improvement in the visible light sensitivity of Ga 2 O 3 nanosheets.…”

Electrochemical Investigation of Interfacial Properties of Ti3C2Tx MXene Modified by Aryldiazonium Betaine Derivatives

“…Several breakthroughs in MXene synthesis and MXene-nanocomposite preparation resulted in various elemental compositions and surface functional tunabilities (Khazaei et al, 2019 ). During the last few years, MXenes have played an ever important role in terms of both crystalline and composition varieties for catalysis (Zhang et al, 2018 ; Benchakar et al, 2019 ; Li and Wu, 2019 ; Sun et al, 2019 ), environmental applications (Rasool et al, 2019 ), development of Li batteries (Ostadhossein et al, 2019 ; Wu Y.-Y. et al, 2019 ), and (bio)sensors (Kalambate et al, 2019 ; Lorencova et al, 2019 ; Mohammadniaei et al, 2019 ; Wu Q. et al, 2019 ; Gajdosova et al, 2020 ; Szuplewska et al, 2020 ).…”