Ultrathin Carbon Deficient Molybdenum Carbide (α-MoC_1–x) Enables High-Rate Mg-Ion-based Energy Storage

Abstract

Dual-electron transfer with Mg 2+ -ion intercalation outperforms typical alkali metal-ion (Li + , Na + , K + ) systems with superior charge storage efficiency while the neutral electrolytes can achieve a working voltage beyond the hydrolysis window of 1.23 V. Hence, aqueous Mg-ion electrolytes are promising for electrochemical energy storage devices to boost the energy density and solve the safety challenges synchronously. However, the Mg-based electrochemical energy storage (EES) devices are generally confined by poor rate performance due to the slow Mg 2+ diffusion in the electrode materials. In this paper, we demonstrate that carbon-deficient carbide could function as a promising electrode material in Mg 2+ -ion-based EES. An electrode made of such carbide can operate over an extended window up to 2.4 V in 1 M magnesium acetate, showing superior performance of high capacitance (125.2 F/g), high energy density (25.1 Wh/ kg), and high power density (3934.8 W/kg). Ab initio simulation reveals migration energy of Mg 2+ being lower than that of Li + diffusing from one carbon defect to another in the α-MoC 1−x lattice, supporting the experimental results that a symmetric supercapacitor made of α-MoC 1−x in an electrolyte based on Mg 2+ outperforms electrolytes based on Li + .

Insight Understanding of Ultrathin Carbon-Deficient Molybdenum Carbide Catalytic Activity for CO2 Conversion into Hydrocarbon Fuels

“…To verify the reliability of the simulation results, we carried out the CO 2 RR experiment with the MoC 0.66 catalyst. The MoCl 5 hydrogel was carbonized layer by layer through laser ablation to produce the ultrathin MoC 0.66 . , There are some porous structures from ∼10 nm to ∼1 μm distributed in different areas of the MoC 0.66 (Figure S4a). The diffraction pattern results (Figure S4b) indicate that a lattice constant of the MoC 0.66 is 4.25 Å .…”

“…The diffraction pattern results (Figure S4b) indicate that a lattice constant of the MoC 0.66 is 4.25 Å . Moreover, the high-angle annular dark-field (HAADF) results (Figure S4c) reveal that the carbide sheets are regularly arranged in alternating darker and brighter phases with a crystalline size of approximately 5 nm, and there are plenty of carbon defects in the laser-ablated product, proving the existence of an ultrathin morphology in the experimentally synthesized MoC 0.66 , which is in great agreement with the previous research . An increasing trend of CO 2 conversion (from ∼0.1 to ∼5% under a pressure of 2 MPa for 1 h), representing the better catalytic property of the MoC 0.66 , has been observed by raising the temperature (Figure S5).…”

Laser Processing of Flexible In-Plane Micro-supercapacitors: Progresses in Advanced Manufacturing of Nanostructured Electrodes

“…Recent studies have shown that laser irradiation of GO or gelatin-mediated hydrogels/inks containing transition metal ions (Mo 5+ , W 6+ , Co 3+ , V 5+ , etc.) on flexible substrates enable multifunctional TMC-based composites for use in flexible devices including in-plane MSCs. − In 2018, Zang et al proposed and demonstrated direct laser writing of Mo 5+ /gelatin-mediated ink-soaked paper substrates using a CW mid-infrared CO 2 laser under an air ambient environment. The resulting product was confirmed to be Mo 3 C 2 and LIG composite characterized by the Raman spectrum and XRD pattern.…”

First‐Principles Investigation of Phase Stability in Substoichiometric Zirconium Carbide under High Pressure

“…[ 17–24 ] This property is known as sub‐stoichiometry, and it plays a vital role in determining bulk properties across many material classes. [ 25–28 ]…”

“…[17][18][19][20][21][22][23][24] This property is known as sub-stoichiometry, and it plays a vital role in determining bulk properties across many material classes. [25][26][27][28] While the presence of vacancies in the dilute limit (≈ 10 −3 ) is usually not sufficient to significantly influence most bulk properties, the concentration of vacancies possible in sub-stoichiometric materials (≈ 10 −1 ) can impart quite considerable effects. For example, vacancy concentration correlates to hardness, [14,29,30] thermal conductivity, [31,32] ionic diffusion, [33,34] and electrical conductivity.…”