Studies On Advanved Catalysts For Nickel-hydrogen Gas Batteries

Since the beginning of the electrical age,humanity’s dependence on electricity has consistently increased.The increasing energy consumption and rising environmental concerns have driven people to decrease their dependence on fossil fuels and foster the development of renewable energy alternatives.While the wind and solar industries have grown rapidly over the past few decades,their contribution to global electricity supply remains relatively modest due to their inherent volatility and intermittency.The Chinese government has established goals to reduce carbon emissions and achieve carbon neutrality,emphasizing the importance of transforming China’s energy structure.In order to promote the development of clean and sustainable renewable energy,it is crucially necessary to develop efficient energy storage systems capable of addressing the intermittent nature of renewables.Despite high expectations for battery energy storage technologies,grid-scale energy storage applications face several challenges,including insufficient safety,low energy density,technological immaturity,and high costs.Nickel-hydrogen gas(Ni-H2)batteries have been utilized as energy storage units in satellites and spacecraft since the 1970s.These batteries employ highly efficient and durable hydrogen catalytic anodes and nickel hydroxide cathodes,meeting the stringent aerospace requirements with their excellent safety,long cycle life,high energy efficiency,all-climate availability,and maintenance-free operation.However,the high amount of platinum(Pt)used in hydrogen catalytic electrodes hinder their grid-scale energy storage application.Therefore,Low-cost,high-efficiency hydrogen catalysts are the important keys to achieving Ni-H2 battery technology for grid-scale energy storage.Hydrogen catalysts can be divided into non-noble and noble metal-based catalysts.Most of the non-noble metal-based catalysts have low mass activity and poor utilization in electrodes,resulting in poor performance in Ni-H2 batteries.For noble metal catalysts,due to their scarce resources and high prices,the grid-scale energy storage applications can only be achieved by greatly improving their mass activity.In addition,scalability of preparation methods of catalysts is also the key for industrialization.This dissertation aims to design a series of low-cost,high active hydrogen catalysts and catalytic electrodes for Ni-H2 batteries.The research is carried out from multiple perspectives,such as improving the catalyst activity,increasing the catalyst utilization,and optimizing the preparation methods.The obtained catalysts are then assembled into NiH2 batteries and tested their performance at industrial-level areal capacity.The main contents of this dissertation are described is as following:1.Highly active non-noble metal nickel-molybdenum(NiMo)hydrogen catalysts were prepared for Ni-H2 cells.We have synthesized a low-cost NiMo alloy,which exhibited higher hydrogen evolution reaction/hydrogen oxidation reaction(HER/HOR)activities than most of the non-noble metal-based catalysts reported so far.In addition,the NiMo alloy catalysts showed a significantly lower elemental cost that is three three orders of magnitude lower than that of Pt.Furthermore,we used hydrophobic multiwalled carbon nanotubes(MWCNTs)in the electrode to form a conductive and gasconducting network which accelerate the electron conduction and hydrogen gas transfer in the HER/HOR process.Compared with the pristine NiMo electrode,the NiMoMWCNT electrode increased the energy efficiency of the cell from 74%to 87%at a current density of 4 mA cm-2.The Ni-H2 battery using the new NiMo electrode exhibited a high energy density of 118 Wh kg-1 and a cost of about 472.5 RMB per kWh.Moreover,there was no significant capacity degradation after 200 cycles,showing remarkable application potential.This study provides the guidance for the development of non-noble metal-based hydrogen catalysts with a practical concept.2.Ultra-high active carbon-loaded ruthenium-nickel alloy nanoparticles(RuNi/C)were prepared for Ni-H2 batteries.The Ni-H2(RuNi)batteries showed an energy efficiency above 75%at a high current density of 50 mA cm-2,and it showed excellent durability for 1500 cycles.Moreover,the cell showed all-climate application in the temperature range of-25℃ to+50℃.Notably,the Ni-H2(RuNi)battery achieves an cell-level energy density up to 183 Wh kg-1 under an ultrahigh cathode Ni(OH)2 loading of 280 mg cm-2(60 mAh cm-2)and a low anode Ru loading of～62.5 μg cm-2,thereby reaching an estimated cost of the cell stack as low as 347 RMB per kWh.This study provides prospects for the development of Ru-based hydrogen catalysts and highperformance Ni-H2 cells.3.A facile and simple synthesis method were proposed for the preparation of bifunctional hydrogen catalytic electrodes.Using the spontaneous corrosion reaction of the metal foam in the metal chloride salt solution,we achieved the simultaneous preparation of catalyst and electrode.In terms of electrochemical performance,the Ru nanoparticles on Ni(OH)2 nanosheets grown on nickel foam(Ru-Ni(OH)2/NF)electrode exhibited excellent a superior HER/HOR catalytic performance than that of Pt/NF electrode.Theoretical calculations showed that Ru-Ni(OH)2 heterojunctions optimized hydrogen adsorption,water dissociation and*OH adsorption,ensuring high HER/HOR activity of the electrode.Microscopic analysis showed that Ru-Ni(OH)2 are robustly grown on the surface of the nickel foam,demonstrating a durable hydrogen electrode.From a cost perspective,the cost of Ru-Ni(OH)2/NF electrode is about 1/15 of that of Pt/NF electrode.This study will become an important reference for the novel preparation of excellent hydrogen catalysts for Ni-H2 batteries.