Theoretical investigation of the MXene precursors MoxV4-xAlC3 (0 ≤ x ≤ 4)

Abstract

By first-principles total-energy calculations, we investigated the thermodynamic stability of the MAX solid solution MoxV4-xAlC3 in the 0 ≤ x ≤ 4 range. Results evidence that lattice parameter a increases as a function of Mo content, while the c parameter reaches its maximum expansion at x = 2.5. After that, a contraction is noticed. Mo occupies VI sites randomly until the out-of-plane ordered Mo2V2AlC3 alloy is formed. We employed the Defect Formation Energy (DFE) formalism to evaluate the thermodynamic stability of the alloys. Calculations show five stable compounds. At V-rich conditions and from Mo-rich to Mo-moderated conditions, the pristine V4AlC3 MAX is stable. In the region of V-poor conditions, from Mo-rich to Mo-moderated growth conditions, the solid solutions with x = 0.5, 1, and 1.5 and the o-MAX Mo2V2AlC3 are thermodynamically stable. The line profiles of the Electron Localization Function and Bader charge analysis show that the V-C interaction is mainly ionic, while the Mo-C is covalent. Also, the exfoliation energy to obtain a MXene layer is ~ 0.4 eV/Å2. DFE also shows that MXenes exfoliated from the MAX phase with the same Mo content and atomic arrangement are thermodynamically stable. Our results get a deeper atomic scale understanding of the previously reported experimental evidence.

Synthesis and applications of double metal MXenes: A review

“…For instance, in Fig. 1, the stability of Mo x V 4-x C 3 is shown for different values of x [21]. According to this figure, V 4 C 3 is stable throughout the molybdenum-containing region.…”

Insights about AlP (001) Surface Reconstructions: A Density Functional Theory Study

“…The thermodynamic analysis is useful to determine the stability of different structures because it depends only on the chemical potential. Therefore, since we are interested in the thermodynamic stability of the AlP (001) surfaces, in this work we employed the so-called surface formation energy (SFE) formalism, which has been adapted to our system following refs − . To apply the formalism, thermodynamic equilibrium between the bulk and the surface is assumed, which implies that μ Al bulk + μ normalP bulk − normalΔ H normalf AlP = μ AlP bulk = μ Al + μ normalP with μ Al ≤ μ Al bulk and μ normalP ≤ μ normalP bulk where μ i is the chemical potential of the i th species and Δ H f AlP is the heat of formation for the AlP compound.…”

Nb2C and Nb2CO2 MXenes as Anodes in Li-Ion Batteries: A Comparative Study by First-Principles Calculations

“…Moreover, recent investigation affirms that the intercalation pseudocapacitance, which employs crystalline structures as electrode materials, provides a higher energy density than under-potential and redox pseudocapacitance . Notably, low-dimensional materials as electrodes are being proposed as the next generation of Li-ion batteries due to the high surface reactivity because it improves the adsorption of adatoms and molecules . Besides, organic 2D materials are emerging candidates for Li-ion batteries .…”

“… 3 Notably, low-dimensional materials as electrodes are being proposed as the next generation of Li-ion batteries due to the high surface reactivity because it improves the adsorption of adatoms and molecules. 4 Besides, organic 2D materials are emerging candidates for Li-ion batteries. 5 On the other hand, the reuse of electrodes from retired Li-ion batteries is an option for recycling components since electrodes can be employed in Na-ion batteries.…”