reaction (HER) are coupled in the single compartment between two electrodes, in which the inherent co-generation of oxygen and hydrogen inevitably hinders the operational flexibility and increases the practical cost. [3] Therefore, it is urgent to develop a feasible electrolyzer system to separately produce and collect hydrogen.Decoupled water electrolysis, firstly proposed by Symes and Cronin, [4] is an effective strategy to achieve gas separation by inducing redox mediators. The mediators with appropriate redox potentials can couple with OER and offer electrons and protons for subsequent hydrogen evolution reaction (HER), which can completely decouple HER and OER in spatial and temporal separation with three-electrode system. [5] To date, many types of redox mediators have been developed to decouple HER and OER, with the neglection of energy requirement. The high energy consumption in above water electrolysis, derived from the sluggish kinetics of anodic OER is unavoidable, [6] where higher than 1.6 V input energy is required because of the high theoretical water electrolysis voltage of 1.23 V. [7] Recently, small molecule organics including alcohols, urea, glucose, hydrazine, etc, have been developed as favorable fuel candidates to replace OER due to the lower overpotentials. [8] Among them, hydrazine, a carbonfree and environmentally friendly liquid fuel, can be oxidized by transition metal catalysts at the low voltage of −0.33 V, effectively decreasing the input electrical energy. [9] Besides the much lower voltage, hydrazine oxidation reaction (HzOR) only releases inert and environmentally benign nitrogen. [9c,d,10] Although the energy for electrolytic hydrogen generation can be significantly decreased via replacing OER by HzOR, the extra energy input is still required to drive the electrolysis, adverse to practical and economical applications. Therefore, it is highly desired to develop a decoupled electrolyzer system for efficient hydrogen generation.Encouraged by the Zn-CO 2 batteries combined resource utilization/production with energy storage system, [11] a rechargeable alkaline Zn-Hz battery, based on decoupled hydrazine splitting by two temporally separate cathodic reactions of HzOR at charging and HER at discharging, can achieve efficient and separate hydrogen generation. Totally different from the typical decoupled electrolysis, the decoupled hydrazine splitting in the Zn-Hz battery is realized by bifunctional electrocatalysts with two-electrode system based on two separate electrochemical ). This Zn-Hz battery, driven by temporally decoupled electrochemical hydrazine splitting on the cathode during discharge and charge processes, can generate separated hydrogen without purification. When the highly active bifunctional cathode of 3D Mo 2 C/ Ni@C/CS is paired with Zn foil, the Zn-Hz battery can achieve efficient hydrogen generation with a low energy input of less than 0.4 V (77.2 kJ mol −1 ) and high energy efficiency of 96%. Remarkably, this battery exhibits outstanding long-term stability f...

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The quench characteristic is a critical issue for the application of superconducting cable. In order to study the process of the quench behavior in the cable accurately, a four-dimensional (4D) quench model for quasi-isotropic superconducting cable was developed and presented, in this paper. We first consider that the materials of the cable are in perfect thermal contact with the neighboring ones, and the radial temperature field and current redistribution at different time and different axial distances during the quench process are obtained. Then, thermal contact resistance (TCR) is considered. In addition, the minimum quench energy (MQE) and the quench propagation velocity (QPV) in axial direction of the two cases are investigated and compared. The results show that the maximum temperature of the heating area (T max ) is higher and QPVs are greater than the case without considering TCR. In addition, there is temperature gradient in the cross section of the cable. Finally we evaluate the sensitivity of thermal stability for the quasi-isotropic cable on the different values of TCR and positions where TCR is inserted. It is concluded that TCR among REBCO tapes has little effect on MQE and QPV of quasi-isotropic superconducting cable. The results are useful for the application of the quasi-isotropic superconducting cable immersed in liquid nitrogen, and this numerical model can also be used for simulating the quench process of other superconducting cables or conductors.

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