【作者】 袁铁锤；

【导师】 周科朝；

【作者基本信息】 中南大学 ， 材料学， 2008， 博士

【摘要】 电解水制氢是现有成熟制氢技术中最具应用前景的一种。但目前使用的Fe电极和Raney-Ni电极由于其较高的析氢过电位导致制氢能耗偏高,因此,要实现大规模开发应用氢能,必须大幅降低析氢阴极的过电位。Ni-S及其多元合金电极因其较低的析氢过电位而成为制氢阴极的研究热点。本文通过在不同镍基体上电沉积制备非晶态Ni-S和Ni-S型三元合金电极,并研究其晶体结构和析氢性能,得到如下研究结果:1、以镍丝网为基体制备了Ni-S合金电极。确定了最佳的电镀液配方和工艺条件。对其析氢性能的研究表明:镀层中S含量对电极的析氢性能影响较大,S含量范围为15-19 wt%时,Ni-S合金电极具有很低的析氢电位。2、选用泡沫镍为基体制备了非晶态Ni-S型合金电极,泡沫镍特殊的多孔网状结构使电极具有更大的真实表面积,析氢活性明显提高,在模拟工业条件下电解24小时后,该电极比Raney-Ni电极的小室电压分别降低0.17V(200mA cm^-2)或0.26V(400mA cm^-2),极大地降低了电解制氢能耗,可产生巨大的经济效益。3、在Ni-S合金镀液中加入Co、La、Mo等过渡族金属元素制得了Ni-S型三元合金电极,实验结果表明:添加上述金属离子均能提高泡沫镍基非晶态Ni-S型合金电极的析氢活性,但只有Ni-S-Co和Ni-S（La）两种三元合金电极具良好的析氢活性和电化学稳定性,在电解水制氢工业中具有较高的实际应用价值。4、采用梯度电沉积工艺制备出镀层中S含量呈梯度分布的泡沫镍基Ni-S合金电极和S、Co含量呈梯度分布的Ni-S-Co合金电极,这种梯度分布形式有利于降低镀层内应力、增加镀层与基体的结合力,提高电极的寿命和稳定性,是一种应用前景良好的析氢阴极材料。5、在Ni-S合金电沉积液中添加稀土氧化物Er₂O₃或Pr₂O₃的研究表明:镀层的晶粒尺寸随添加物浓度的增大而有所减小,这可能是Pr₂O₃或Er₂O₃颗粒在电极表面的吸附阻碍了晶核生长,导致镀层晶粒尺寸减小,表面积增大,Er₂O₃或Pr₂O₃的加入有利于提高电极的析氢活性。6、对Ni-S合金电极的镀后处理工艺结果表明:液相热活化处理可极大地提高电极的析氢活性,降低析氢电位;而氩气热处理使合金镀层由非晶态转变为晶态结构,析氢电位反而有所升高。7、通过Tafel曲线计算出泡沫镍电极、泡沫镍基Ni-S合金电极和Ni-S-Co合金电极的表观活化能分别为49.5 kJ mol^-1、40.3 kJ mol^-1和38.6 kJ mol^-1,首次从能量角度上揭示了各合金电极析氢活性不同的原因。对Ni-S型合金电极析氢反应的研究结果表明:电极在析氢过程中能大量吸附氢原子是电极活性高的根本原因;其析氢反应的催化机理为电化学脱附机理。更多还原

【Abstract】 In all the mature hydrogen production techniques the water electrolytic production of the hydrogen energy is the most applicable technique.However,the iron and Raney-nickel electrode of the electrolytic technique used nowadays result in high energy consumption due to the high hydrogen evolution reaction（HER） potential.Thus,to develop and use the hydrogen energy in large scale,the HER potential must be decreased.Recently,Ni-S and Ni-S-based alloys have gain important considerations in hydrogen production field due to the low HER potential.In this paper,the amorphous Ni-S and Ni-S-based tertiary alloy electrode have been produced on different nickel substrates,and the crystal structures and the hydrogen evolution activity have been studied. Based on the investigations,the following conclusions are drawn:1.Ni-S alloy electrode on nickel net substrate has been produced. The best electrodepositing conditions have been experimentally determined.The results of the hydrogen evolution properties indicated that the content of S in the coating has large effect on the hydrogen evolution properties of the electrode.The Ni-S alloy electrode has very low HER potential when the content of S is between 15～19%.2.The amorphous Ni-S alloy electrode has been produced on nickel foam substrate.Compared to nickel net substrate,the hydrogen evolution properties of nickel foam substrate have obviously been improved since the nickel foam substrate has special pore structures and large true surface area.In modeling the industrial electrolysis conditions for 24 hours,the cell volt of the nickel foam substrate was decreased by 0.17 V and 0.26 V at current densities of 200 mA·cm^-2 and 400 mA·cm^-2,respectively,which substantially decreases the energy consumption in electrolytic production of hydrogen.3.Ni-S-based tertiary alloy electrodes have been produced by adding Co,La and Mo ions.The experimental results indicated that all the above mentioned metal ions can improve the hydrogen evolution activity of nickel foam substrate based amorphous Ni-S alloy electrode.However, only Ni-S-Co and Ni-S-La alloy electrodes have both excellent hydrogen evolution properties and electro-chemical stability,and have high real application merit for hydrogen electrolytic production industry.4.On the first time,the Ni-S electrode with gradient distribution of S and the Ni-S-Co electrode with gradient distributions of S and Co in the coating have been produced using gradient electrolytic process.This gradient distribution can help decrease the coating internal stress and increase the coherence between the coating and the substrate,and improve the electro-chemical stability and lifetime.Thus,they are good hydrogen evolution cathode materials for future applications.5.The rare earth element oxides Er₂O₃ and Pr₂O₃ have been added to the electroplating solution.The experimental results indicated that the grain size of the coating decreases and surface area increases as the concentration of the additives increase,which is probably due to the inhibition of the grain growth by Er₂O₃ and Pr₂O₃ particles on the coating surface.However,the addition of the Er₂O₃ or Pr₂O₃ can help improve the hydrogen evolution activity.6.The heat treatment program after electrodeposition has been studied.It has been shown that Ni-S alloy coating can change from amorphous state to crystalline state after heat treatment under argon atmosphere,thus increase the HER potential,while the HER potential during water electro-deposition can be decreased a lot after heat treatment under alkali solution.7.The calculated activation energies are 49.5,40.3 and 38.6 kJ mol^-1 for nickel foam electrode,nickel foam substrate based Ni-S alloy electrode and Ni-S-Co alloy electrode according to Tafel curves, respectively,which gives explanation about the difference in hydrogen evolution activity from energy angle.The results indicated that the high hydrogen evolution activity of Ni-S alloy electrode is due to the large absorption of the hydrogen atoms during hydrogen evolution process.The catalysis principle is electro-chemical desorption principle.更多还原