Aqueous rechargeable hydrogen gas batteries have low cost and high safety, which are expected to be used in large-scale energy storage. Here, we design a novel static vanadium-hydrogen gas (V-H) battery by pairing V3+/VO2+ liquid redox cathode with the hydrogen gas anode. The two-electron reactions between V3+ and VO2+ in static hydrogen gas batter. Hydrogen gas batteriesVanadium cathodeHigh current densityLarge-scale energy storageWith the rapid evolution of renewable energy, there is an urgent demand for developing large-scale electrical energy storage systems with good reliability, fast rate, and high safety to compensate for the intermittency and volatility of sustainable wind and solar powers,,. Currently, lithium-ion batteries are widely used in electronic devices and electrical vehicles due to their mature manufacturing and high energy density,,. However, the use of flammable organic electrolytes increases the safety risk, making them unsuitable for large-scale energy storage. In contrast, aqueous rechargeable batteries are increasingly favored in the large-scale energy storage area due to their advantages of good stability, eco-friendliness, and cost-effectiveness [7,8]. For example, lead-acid batteries have achieved great success in commercialization with the advantages of high safety and low cost. However, their further development is limited by the low energy density and poor cycle life [9,10]. In addition, redox flow batteries exhibit long-term cycling performance, but their fabrication process is cumbersome due to the needs of additional pumps and storage tanks [11,12]. Therefore, it is necessary to develop new aqueous battery systems with high energy density and facile manufacturing process to perfectly match the future grid energy storage.Recently, Chen's group has successfully initiated and developed a category o. 2.1. Fabrication of the Swagelok cellThe Pt/C powder (20 % Pt on Vulcan XC-72, Premetek, USA) and polyvinylidene fluoride (MTI) were evenly dispersed in N-methyl-2-pyrrolidone (NMP, Aladdin) with a mass ratio of 9:1 to form a slurry. Subsequently, the slurry was coated on a gas diffusion layer with doctor blading and dried at 80 °C for 12 h to form a hydrogen anode. The mass loading of Pt/C was controlled to be ∼1 mg/cm2. The carbon felt was used as a liquid cathode after being calcined at 450 °C for 2 h. The electrolyte was 1.5 mol/L VOSO4 with 3 mol/L H2SO4 or 1.8 mol/L VOSO4 with 3 mol/L H2SO4. The Nafion 117 membrane (Dupont, USA) was soaked in 3 % H2O2 at 80 °C for 1 h and then washed in deionized water at 80 °C for 1 h. Finally, the membranes were treated with 3 mol/L H2SO4 at 80 °C for 1 h to change them into H+ conductive membranes. Both cathode and anode have an area of 1 cm2. The Swagelok cells were assembled according to a previous study [13,17]. The V-H batteries were assembled by a homemade Swagelok cell composed of stainless-steel inlet and outlet valves with Klein Flange (KF) to Swagelok adapters in a polytetrafluoroethylene (PTFE)-centered O-ring by a clamp. Inside the cell, the liquid cathode, Nafion 117 membrane and hydrogen anode were assembled in a sandwiched structure in a coin-cell-like stack. And a glass fiber membrane wa. 3.1. Fabrication and electrochemical performance of the V-H batteryFig. 1 illustrates the structure and charge and discharge processes of the V-H battery. Specifically, a carbon felt was selected as the liquid-phase cathode for the V3+/VO2+ redox reaction and Pt/C catalyst coated on gas diffusion layer as anode for HER/HOR. A Nafion membrane was used as the separator to transport H+ and prevent the crossover of V ions between the electrodes. During the first charge, V4+ is oxidized to VO2+ on the cathode, while HER occurs at the anode. During the discharge, VO2+ is reduced to V3+ at the cathode, while HOR happens on the anode. In the subsequent cycles, the anode is still based on HER/HOR and the cathode is a two-electron conversion reaction of V, where V3+ is firstly oxidized to VO2+ and then further oxidized to VO2+. The discharge process is exactly the reverse process of the charge process. The working principle of the V-H battery can be described in the following equations:(1)First charge of cathode: V4+ + 2H2O → VO2+ + 4H+ + e−(2)Subsequent cycles of cathode: V3+ + 2H2O ↔ VO2+ + 4H+ + 2e−(3)Anode: 2H+ + 2e− ↔ H2(4)Overall: V3+ + 2H2O ↔ VO2+ + 2H+ + H2Fig. 1. The working principle of V-H battery with charge and discharge processes.The electrochemical performance of the V-H battery was systematically investigated in a homemade Swagelok cell. In order to underst.
