Molten salt derived Mo₂AlB₂ with excellent HER catalytic performance

Mo2AlB2 is a lamellar transition metal boride that is prepared by selectively etching the MoAlB MAB phase precursor. Most methods for synthesizing Mo2AlB2 require the use of strong acids or bases and a long reaction time. In this study, we present a Lewis acid molten salt method for synthesizing the lamellar structured Mo2AlB2 by selectively etching a layer of aluminium atoms from the MoAlB precursor. The synthesized Mo2AlB2 shows excellent catalytic activity for hydrogen evolution reaction under alkaline conditions, with long-term stability, and a low overpotential of 145 mV and Tafel slope of 76 mV dec−1 at 10 mA cm−2. Mo2AlB2 was synthesized through a novel molten salt method of etching MoAlB, resulting in exceptional HER catalytic performance in alkaline conditions.</p

Selenium Embedded in Metal–Organic Framework Derived Hollow Hierarchical Porous Carbon Spheres for Advanced Lithium–Selenium Batteries

Metal–organic framework derived hollow hierarchical porous carbon spheres (MHPCS) have been fabricated via a facile hydrothermal method combined with a subsequent annealing treatment. Such MHPCS are composed of masses of small hollow carbon bubbles with a size of ∼20 nm and shells of ∼5 nm thickness interconnected to each other. MHPCS/Se composite is developed as a cathode for Li–Se cells and delivers an initial specific capacity up to 588.2 mA h g^–1 at a current density of 0.5 C, exhibiting an outstanding cycling stability over 500 cycles with a decay rate even down to 0.08% per cycle. This material is capable of retaining up to 200 mA h g^–1 even after 1000 cycles at a current density of 1 C. Such good electrochemical performance may be ascribed to the distinct hollow structure of the carbon spheres and a large amount of Se wrapped within small carbon bubbles, thus not only enhancing the electronic/ionic transport but also providing additional buffer space to adjust volume changes of Se during charge/discharge processes

Improving the Performance of Hard Carbon//Na₃V₂O₂(PO₄)₂F Sodium-Ion Full Cells by Utilizing the Adsorption Process of Hard Carbon

Hard carbon has been regarded as a promising anode material for Na-ion batteries. Here, we show, for the first time, the effects of two Na⁺ uptake/release routes, i.e., adsorption and intercalation processes, on the electrochemical performance of half and full sodium batteries. Various Na⁺-storage processes are isolated in full cells by controlling the capacity ratio of anode/cathode and the sodiation state of hard carbon anode. Full cells utilizing adsorption region of hard carbon anode show better cycling stability and high rate capability compared to those utilizing intercalation region of hard carbon anode. On the other hand, the intercalation region promises a high working voltage full cell because of the low Na⁺ intercalation potential. We believe this work is enlightening for the further practical application of hard carbon anode

Activating Pseudocapacitive Charge Storage of Molten-Salt-Synthesized MXenes in Mild Aqueous Electrolytes

Traditional MXenes, synthesized by an HF-based wet chemical process, are promising pseudocapacitive materials in strong acidic aqueous electrolytes, but they show poor performance in neutral or alkaline aqueous electrolytes due to the lack of pseudocapacitive activity. In this work, we demonstrate that molten-salt-synthesized MXenes (MS-MXenes) with −O and −Cl surface groups can exhibit a high pseudocapacitive behavior in both AlCl3 and acetate-buffered aqueous electrolytes. MS-Ti2CTx MXene achieves a high specific capacitance of 318 C g–1 in a 1 M AlCl3 electrolyte and 280 C g–1 in a 1 M acetate buffer electrolyte. Furthermore, the mild acidity of AlCl3 and acetate electrolytes suppresses hydrogen evolution and enables more negative cutoff potentials of −1.6 and −1.4 V versus Hg/Hg2SO4, respectively. Most of the charge storage and release occur at potentials below −1 V versus Hg/Hg2SO4, making MS-MXene carbides suitable for negative electrodes. By pairing with a MnO2 positive electrode, the asymmetric supercapacitor delivers a high voltage of 2.1 V and an energy density of 37 Wh kg–1 together with high cycling stability in a 1 M acetate aqueous electrolyte. Our findings demonstrate the potential of MXenes as negative electrode materials in mild aqueous electrolytes, opening avenues for their practical implementation in advanced energy storage devices

Synergistic Effects of Pyrrolic N/Pyridinic N on Ultrafast Microwave Synthesized Porous CoP/Ni₂P to Boost Electrocatalytic Hydrogen Generation

Transition metal phosphides are ideal inexpensive electrocatalysts for water-splitting, but the catalytic activity still falls behind that of noble metal catalysts. Therefore, developing valid strategies to boost the electrocatalytic activity is urgent to promote large-scale applications. Herein, a microwave combustion strategy (20 s) is applied to synthesize N-doped CoP/Ni2P heterojunctions (N-CoP/Ni2P) with porous structure. The porous structure expands the specific surface area and accelerates the mass transport efficiency. Importantly, the pyrrolic N/pyridinic N content is adjusted by changing the amount of urea during the synthesis process and then optimizing the adsorption/desorption capacity for H*/OH* to enhance the catalyst activity. Then, the synthesized N-CoP/Ni2P exhibits small overpotentials of 111 and 133 mV for HER in acidic and alkaline electrolytes and 290 mV for OER in alkaline electrolytes. This work provides an original and efficient approach to the synthesis of porous metal phosphides

Synergistic Effects of Pyrrolic N/Pyridinic N on Ultrafast Microwave Synthesized Porous CoP/Ni₂P to Boost Electrocatalytic Hydrogen Generation

Transition metal phosphides are ideal inexpensive electrocatalysts for water-splitting, but the catalytic activity still falls behind that of noble metal catalysts. Therefore, developing valid strategies to boost the electrocatalytic activity is urgent to promote large-scale applications. Herein, a microwave combustion strategy (20 s) is applied to synthesize N-doped CoP/Ni2P heterojunctions (N-CoP/Ni2P) with porous structure. The porous structure expands the specific surface area and accelerates the mass transport efficiency. Importantly, the pyrrolic N/pyridinic N content is adjusted by changing the amount of urea during the synthesis process and then optimizing the adsorption/desorption capacity for H*/OH* to enhance the catalyst activity. Then, the synthesized N-CoP/Ni2P exhibits small overpotentials of 111 and 133 mV for HER in acidic and alkaline electrolytes and 290 mV for OER in alkaline electrolytes. This work provides an original and efficient approach to the synthesis of porous metal phosphides