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1. One-step hydrothermal synthesis of porous Ti ₃ C ₂ T _z MXene/rGO gels for supercapacitor applications

   https://doi.org/10.1039/D1NR02114A  

   Saha, Sanjit; Arole, Kailash; Radovic, Miladin; Lutkenhaus, Jodie L.; Green, Micah J. (October 2021, Nanoscale)

   Titanium carbide/reduced graphene oxide (Ti 3 C 2 T z /rGO) gels were prepared by a one-step hydrothermal process. The gels show a highly porous structure with a surface area of ∼224 m 2 g −1 and average pore diameter of ∼3.6 nm. The content of GO and Ti 3 C 2 T z nanosheets in the reaction precursor was varied to yield different microstructures. The supercapacitor performance of Ti 3 C 2 T z /rGO gels varied significantly with composition. Specific capacitance initially increased with increasing Ti 3 C 2 T z content, but at high Ti 3 C 2 T z content gels cannot be formed. Also, the retention of capacitance decreased with increasing Ti 3 C 2 T z content. Ti 3 C 2 T z /rGO gel electrodes exhibit enhanced supercapacitor properties with high potential window (1.5 V) and large specific capacitance (920 F g −1 ) in comparison to pure rGO and Ti 3 C 2 T z . The synergistic effect of EDLC from rGO and redox capacitance from Ti 3 C 2 T z was the reason for the enhanced supercapacitor performance. A symmetric two-electrode supercapacitor cell was constructed with Ti 3 C 2 T z /rGO, which showed very high areal capacitance (158 mF cm −2 ), large energy density (∼31.5 μW h cm −2 corresponding to a power density of ∼370 μW cm −2 ), and long stability (∼93% retention) after 10 000 cycles. 

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2. Enhanced charge storage of nanometric ζ-V ₂ O ₅ in Mg electrolytes

   https://doi.org/10.1039/d0nr05060a  

   Johnson, Ian D.; Nolis, Gene; Yin, Liang; Yoo, Hyun Deog; Parajuli, Prakash; Mukherjee, Arijita; Andrews, Justin L.; Lopez, Mario; Klie, Robert F.; Banerjee, Sarbajit; et al (November 2020, Nanoscale)

   null (Ed.)

   V 2 O 5 is of interest as a Mg intercalation electrode material for Mg batteries, both in its thermodynamically stable layered polymorph (α-V 2 O 5 ) and in its metastable tunnel structure (ζ-V 2 O 5 ). However, such oxide cathodes typically display poor Mg insertion/removal kinetics, with large voltage hysteresis. Herein, we report the synthesis and evaluation of nanosized ( ca . 100 nm) ζ-V 2 O 5 in Mg-ion cells, which displays significantly enhanced electrochemical kinetics compared to microsized ζ-V 2 O 5 . This effect results in a significant boost in stable discharge capacity (130 mA h g −1 ) compared to bulk ζ-V 2 O 5 (70 mA h g −1 ), with reduced voltage hysteresis (1.0 V compared to 1.4 V). This study reveals significant advancements in the use of ζ-V 2 O 5 for Mg-based energy storage and yields a better understanding of the kinetic limiting factors for reversible magnesiation reactions into such phases. 

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3. High performance vacuum annealed β -(Al _x Ga _1−x ) ₂ O ₃ /Ga ₂ O ₃ HFET with f _T /f _MAX of 32/65 GHz

   https://doi.org/10.35848/1882-0786/adeb43  

   Saha, Chinmoy Nath; Nipu, Noor Jahan; Singisetti, Uttam (July 2025, Applied Physics Express)

   Abstract This letter reports high performanceβ- (Al_xGa_1−x)₂O₃/Ga₂O₃Heterostructure FET (HFET) with an improved regrowth process and successful Al₂O₃passivation. Highly scaled I shaped gates (100–200 nm L_G) have been fabricated with degenerately doped (N++) source/drain contact regrown by ozone molecular beam epitaxy (MBE). Aiming to address the limitations observed in previously reported devices, this work incorporates a low-power BCl₃/Ar and SF₆/Ar plasma etching process to remove the AlGaO barrier layer and Ga₂O₃layer respectively before regrowth. Additionally, the surface was cleaned, and vacuum annealing was carried out before MBE regrowth to reduce any interface resistance between highly doped regrowth N++ and 2DEG layer. These meticulously designed fabrication steps enabled us to achieve the high DC current 0.5 A mm⁻¹at 5 V drain bias with 6.1 Ω.mm on resistance (R_ON) at V_GS = 3 V, peak transconductance (g_m) of 110 mS mm⁻¹at room temperature (V_DS = 15 V) and around 0.8 A mm⁻¹(V_DS = 5 V) peak I_ONat low temperature (100 K). The current gain cut-off frequency (f_T) of 32 GHz and peak power gain cut-off frequency (f_MAX) of 65 GHz were extracted from radiofrequency (RF) measurements. The reported f_MAXis one of the highest for Ga₂O₃based RF devices to the best of the authors’ knowledge. The f_T.L_Gproduct was estimated to be 6.1 GHz-μm for 191 nm L_Gand 32 GHz f_T, which is one of the highest reported among Ga₂O₃devices. After passivating the device with thicker Al₂O₃, the device shows no current collapse demonstrating first time successful traps passivation with Al₂O₃forβ-Ga₂O₃devices. 

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4. Facile synthesis of hierarchical MoS ₂ –carbon microspheres as a robust anode for lithium ion batteries

   https://doi.org/10.1039/C6TA03310E  

   Chen, Gen; Wang, Shengping; Yi, Ran; Tan, Longfei; Li, Hongbo; Zhou, Meng; Yan, Litao; Jiang, Yingbing; Tan, Shuai; Wang, Donghai; et al (January 2016, Journal of Materials Chemistry A)

   Molybdenum disulfide (MoS 2 ) may be a promising alternative for lithium ion batteries (LIBs) because it offers a unique layered crystal structure with a large and tunable distance between layers. This enables the anticipated excellent rate and cycling stability because they can promote the reversible lithium ion intercalation and de-intercalation without huge volume change which consequently prevents the pulverization of active materials during repeated charge and discharge processes. Herein, we prepared hierarchical MoS 2 –carbon (MoS 2 –C) microspheres via a continuous and scalable ultrasonic nebulization assisted route. The structure, composition, and electrochemical properties are investigated in detail. The MoS 2 –C microspheres consist of few-layer MoS 2 nanosheets bridged by carbon, which separates the exfoliated MoS 2 layers and prevents their aggregation and restacking, thus leading to improved kinetic, enhanced conductivity and structural integrity. The novel architecture offers additional merits such as overall large size and high packing density, which promotes their practical applications. The MoS 2 –C microspheres have been demonstrated with excellent electrochemical performances in terms of low resistance, high capacity even at large current density, stable cycling performance, etc. The electrodes exhibited 800 mA h g −1 at 1000 mA g −1 over 170 cycles. At a higher current density of 3200 mA g −1 , a capacity of 730 mA h g −1 can be also maintained. The MoS 2 –C microspheres are practically applicable not only because of the continuous and large scale synthesis via the current strategy, but also the possess a robust and integrated architecture which ensures the excellent electrochemical properties. 

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5. Catalyzing zinc-ion intercalation in hydrated vanadates for aqueous zinc-ion batteries

   https://doi.org/10.1039/D0TA01468K  

   Liu, Chaofeng; Tian, Meng; Wang, Mingshan; Zheng, Jiqi; Wang, Shuhua; Yan, Mengyu; Wang, Zhaojie; Yin, Zhengmao; Yang, Jihui; Cao, Guozhong (April 2020, Journal of Materials Chemistry A)

   Hydrated vanadium pentoxide (VOH) can deliver a gravimetric capacity as high as 400 mA h g −1 owing to the variable valence states of the V cation from 5+ to 3+ in an aqueous zinc ion battery. The incorporation of divalent transition metal cations has been demonstrated to overcome the structural instability, sluggish kinetics, fast capacity degradation, and serious polarization. The current study reveals that the catalytic effects of transition metal cations are probably the key to the significantly improved electrochemical properties and battery performance because of the higher covalent character of 55% in the Cu–O bond in comparison with 32% in the Mg–O bond in the respective samples. Cu( ii ) pre-inserted VOH (CuVOH) possesses a significantly enhanced intercalation storage capacity, an increased discharge voltage, great transport properties, and reduced polarization, while both VOH and Mg( ii ) pre-inserted VOH (MgVOH) demonstrate similar electrochemical properties and performances, indicating that the incorporation of Mg cations has little or no impact. For example, CuVOH has a redox voltage gap of 0.02 V, much smaller than 0.25 V for VOH and 0.27 V for MgVOH. CuVOH shows an enhanced exchange current density of 0.23 A g −1 , compared to 0.20 A g −1 for VOH and 0.19 A g −1 for MgVOH. CuVOH delivers a zinc ion storage capacity of 379 mA h g −1 , higher than 349 mA h g −1 for MgVOH and 337 mA h g −1 for VOH at 0.5 A g −1 . CuVOH shows an energy efficiency of 72%, superior to 53% for VOH and 55% for MgVOH. All of the results suggest that pre-inserted Cu( ii ) cations played a critical role in catalyzing the zinc ion intercalation reaction, while the Mg( ii ) cations did not exert a detectable catalytic effect. 

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