Preparation Of Hydrogen Evolution Electrode And Study Of Electrochemical System For Hydrogen Production From Zinc-Water

As the charging and discharging cycle proceeds,the deposited zinc metal on the negative electrode of zinc-nickel single-liquid flow battery will be shed and accumulate at the bottom of the battery,and the performance of the battery will be decayed.Therefore,this project aims to efficiently eliminate the shed zinc and restore the performance of the zinc-nickel single-liquid flow battery by preparing a high catalytic activity hydrogen precipitation electrode,and forming a zinc-water hydrogen production battery from the prepared electrode and zinc,which is accompanied by hydrogen precipitation on the hydrogen precipitation electrode while the zinc is dissolved,and simultaneously outputting electrical power externally.In addition,to improve the output power of the external circuit of the zinc-water battery,the original battery system was improved to enhance the discharge performance of the zinc-water hydrogen production battery under the controlled range of hydrogen rate.The main research of the full paper is as follows:（1）Composite nickel-plated/hydrogen storage alloy（Ni/MH）electrodes were prepared and their hydrogen precipitation performance in alkaline aqueous solutions was investigated.The results of scanning electron microscopy（SEM）,X-ray diffraction（XRD）and energy spectrum analysis（EDS）show that the hydrogen storage alloy particles have been uniformly deposited inside and on the surface of the nickel plating,and there are pores on the surface of the electrode;the overpotential of the Ni/MH composite electrode is 196 m V when the current density reaches 50 m A·cm^-2 and 196 m V when the current density reaches100 m A·cm^-2,as determined by the polarization curve（LSV）at room temperature.The performance of Ni/MH composite electrode is much better than that of Ni-plated electrode,with the overpotential of 231 m V when the current density reaches 100 m A·cm^-2 and the Tafel slope of 100 m V·dec^-1;the chrono-potentiometric（CP）test shows that the potential response of Ni/MH composite electrode is very stable and comparable to that of Pt electrode,while the polarization of Ni electrode continues to increase;the electrochemical impedance spectroscopy（EIS）test confirms that The electrochemical impedance spectroscopy（EIS）test confirmed that the charge transfer resistance of Ni/MH composite electrode was low.The results show that the composite plating with hydrogen storage alloy significantly improves the hydrogen precipitation catalytic performance of the Ni electrode and has a broad application prospect.（2）To investigate the effect of nickel metal surface treatment on the performance of hydrogen precipitation electrode,flat nickel,polished nickel,perforated nickel,rhombic nickel mesh,and nickel foam were used as hydrogen precipitation cathodes and their hydrogen precipitation performance was investigated with the performance of the constructed zinc-water hydrogen cell.The Tafel curves fitted to the LSV polarization curves showed that the Tafel slope of nickel foam was the smallest at 68.7 m V·dec^-1.The two-electrode polarization curves and the fitted power density curves showed that nickel foam had a maximum power density of 8.84 m W/cm².The voltage-time curves for 10m A·cm^-2 constant-current discharge showed that all nickel electrodes with different surface treatments showed performance degradation.Discharging nickel foam at high current densities above 50 m A·cm^-2,the dissolved zinc from the anode is redeposited onto the cathode surface,thus hindering the hydrogen precipitation process.Nickel foam is suitable for deep hydrogen precipitation discharge up to 50 m A·cm^-2 current density,and the discharge voltage voltage of zinc-water hydrogen precipitation cell decreases slowly along with the hydrogen precipitation time.Nickel foam with high specific surface area has superior performance than flat nickel,polished nickel,perforated nickel,and diamond-shaped nickel mesh.（3）In order to improve the electrical output power of zinc-water battery in alkaline solution,an electrolyte-decoupled zinc-water battery that can extend the battery discharge voltage at the same current density is proposed.A Ni-Cu-La Fe O₃ hydrogen precipitation cathode that can operate stably in the electrolyte-decoupled zinc-water cell was prepared.The morphological structure,material type and elemental content of the Ni-Cu-La Fe O₃electrode surface were determined using scanning electron microscopy（SEM）,X-ray diffraction（XRD）and energy spectrum analysis（EDS）characterization.The performance of alkaline solution Zn-water cells and electrolyte-decoupled Zn-water cells were compared by steady-state polarization curves（LSV）and chronopotentiometry（CP）tests,and the causes of performance degradation of alkaline solution Zn-water cells were analyzed by electrochemical impedance（EIS）and chronopotentiometry（CP）in the three-electrode system.The results show that the electrolyte-decoupled zinc-water cell has high electrical output power and stable hydrogen release,which is an efficient,environmentally friendly and inexpensive hydrogen production system with broad application prospects in the field of hydrogen energy.