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Structural schemes of α‐MoO3 bound to (a) Na, (b) Mg and (c) Al atoms along with the corresponding binding energies. Radial distribution functions (g(r)) demonstrating the distribution of distances from Na, Mg and Al atoms to (d) Mo and (e) O atoms in α‐MoO3.
Source publication
In this paper, we show that the electrochemical
performance of -MoO3 electrode is significantly dependent on the
charge density of three studied aqueous electrolyte cations, i.e., Na+,
Mg2+ and Al3+. The charge storage capacity of the -MoO3 electrode
increases with increasing the cation charge density. On the other
hand, the initial coulombic eff...
Citations
... Orthorhombic molybdenum trioxide (a-MoO 3 ) is a layered transition metal oxide [5] that can host a wide range of cations such as H + [6], Na + [7], Mg 2+ [8] and Al 3+ [9]. Moreover, a-MoO 3 material has a high theoretical capacity of 372 mAh/g [8,10]. ...
... Orthorhombic molybdenum trioxide (a-MoO 3 ) is a layered transition metal oxide [5] that can host a wide range of cations such as H + [6], Na + [7], Mg 2+ [8] and Al 3+ [9]. Moreover, a-MoO 3 material has a high theoretical capacity of 372 mAh/g [8,10]. However, the a-MoO 3 electrode material is not stable against cycling in aqueous electrolytes. ...
... Ag/AgCl) (Fig. 2c). This is characteristic of Al 3+ -ion intercalation [8], which suggests that the [Al(H 2 O) 6 ] 3+ species is the major intercalant cation in the SiWE. However, other minor CV peaks appeared which may be attributed to the multivalent species, i.e. ...
Orthorhombic molybdenum trioxide (α-MoO3) electrode material experiences severe capacity fading and poor cycling stability in aqueous electrolytes. We investigated the charge-storage performance of α-MoO3 electrode in aluminium trifluoromethanesulfonate (Al(OTf)3)-based salt-in-water electrolyte (SiWE) and water-in-salt electrolyte (WiSE). It was found that α-MoO3 electrode exhibits significantly different cycling stabilities in both electrolytes with capacity retentions of 8% using the former and 87% using the latter. This is because α-MoO3 electrode maintains its crystal structure upon cycling in WiSE, but experiences substantial structural collapses and partial dissolution upon cycling in SiWE. This behaviour was inferred from both operando electrogravimetry and ex situ analyses. Research results suggest that the predominant charge-storage mechanism in α-MoO3 electrode using WiSE is the intercalation of protons due to electrolyte hydrolysis with some contribution from surface pseudocapacitance enabled by Al³⁺ ions. A two-volt full cell fabricated from α-MoO3 electrode as anode and copper hexacyanoferrate (CuHCF) electrode as cathode using WiSE delivers volumetric and gravimetric energies of 10.4 Wh/L and 26.5 Wh/kg, respectively, with 78% capacity retention after 2500 cycles. This study provides an insightful understanding of the electrochemical performance of α-MoO3 electrode in Al(OTf)3-based electrolytes.
... In a previous work [10], we reported on a stable α-MoO 3 -thin-film electrode for aqueous Na + -ion storage. In a subsequent study [11], we employed the thin-film α-MoO 3 electrode to investigate the effect of the charge density of electrolyte cations, i.e. Na + , Mg 2+ and Al 3+ , on the charge storage capacity. ...
... electrode demonstrated an initial areal discharge capacity of 2.01 mAh/ cm 2 which is equivalent to a specific capacity of ~251 mAh/g MoO3 . The initial coulombic efficiency (ICE) was estimated based on the ratio of the reversible capacity to the sum of reversible and irreversible capacities [11]. The ICE of α-MoO 3 was estimated to be ~28%, suggesting that most of the Al 3+ ions were irreversibly trapped in the α-MoO 3 electrode and/or structural collapses of α-MoO 3 occurred during the initial alumination, i.e., initial Al 3+ -ion insertion. ...
Orthorhombic molybdenum trioxide (α-MoO3) is a promising electrode material for aqueous electrochemical metal-ion storage due to its unique layered structure. However, its poor electronic conductivity and instability in aqueous electrolytes hinder its applications in electrochemical energy storage. In this paper, we report on the synthesis and electrochemical properties of a polypyrrole-stabilised α-MoO3 electrode for aqueous Al³⁺-ion storage. This binder-free, PPy-coated α-MoO3 electrode (α-MoO3@PPy) synthesised using an electrodeposition method has a high mass loading ( ∼16 mg/cm²). The α-MoO3@PPy electrode exhibites a high cycling stability in a 1 M aqueous AlCl3 electrolyte with a capacity retention of 88% after 1000 cycles. A full electrochemical Al³⁺-ion pseudocapacitor cell fabricated with the α-MoO3@PPy as anode and copper hexacyanoferrate (CuHCF) as cathode delivers a high rate capability with energy densities of 0.33 and 0.20 mWh/cm² at current densities of 1 and 10 mA/cm², respectively. In addition, this cell is stable against cycling with a capacity retention of 70% after 1800 cycles. This work provides an approach to the synthesis of stable α-MoO3-based electrode materials for aqueous electrochemical energy storage.
This study focuses on the development and optimization of MoO3 films on commercially available FTO substrates using the pulsed laser deposition (PLD) technique. By carefully selecting deposition conditions and implementing post-treatment procedures, precise control over crystallite orientation relative to the substrate is achieved. Deposition at 450 °C in O2 atmosphere results in random crystallite arrangement, while introducing argon instead of oxygen to the PLD chamber during the initial stage of sputtering exposes the (102) and (011) facets. On the other hand, room temperature deposition leads to the formation of amorphous film, but after appropriate post-annealing treatment, the (00k) facets were exposed. The deposited films are studied using SEM and XRD techniques. Moreover, electrochemical properties of FTO/MoO3 electrodes immersed in 1 M AlCl3 aqueous solution are evaluated using cyclic voltammetry and electrochemical impedance spectroscopy. The results demonstrate that different electrochemical processes are promoted based on the orientation of crystallites. When the (102) and (011) facets are exposed, the Al³⁺ ions intercalation induced by polarization is facilitated, while the (00k) planes exposure leads to the diminished hydrogen evolution reaction overpotential.
Layered crystal materials have blazed a promising trail in the design and optimization of electrodes for magnesium ion batteries (MIBs). The layered crystal materials effectively improve the migration kinetics of the Mg²⁺ storage process to deliver a high energy and power density. To meet the future demand for high‐performance MIBs, significant work has been applied to layered crystal materials, including crystal modification, mechanism investigation, and micro/nanostructure design. Herein, this review presents a comprehensive overview of layered crystal materials applied to MIBs, from development history to current applications. It focuses on the relationship between the layered crystal structure and the energy storage mechanism. Meanwhile, recent achievements in the design principles of layered crystal materials and their application to electrodes are summarized. Finally, future perspectives on the application of layered materials in MIBs are presented. The overview of the development process and structural characteristics contributes to a thorough understanding of these materials, while a discussion of design strategies and practical applications can inspire further research. Therefore, this review provides guidance and assistance for constructing high‐performance MIBs.
