【作者】 李爽；

【导师】 杜希文；

【作者基本信息】 天津大学 ， 材料学， 2019， 硕士

【摘要】 日益严重的能源问题迫切要求我们对绿色能源进行开发和利用。电解水获取氢能是有效方式之一。其中,实现析氢反应（HER）和析氧反应（OER）的双功能电催化剂对于通过整体水分解将水转化为清洁燃料至关重要。双功能催化剂意味着材料需要包含同时满足HER和OER的催化位点,即对H^*和O^*中间体均有最优吸附能。掺杂水滑石材料表现出催化HER和OER的巨大潜力。本文对镍基LDH表面进行HER和OER单独催化位点的设计,以便HER和OER中间体可以被这些位点吸附并独立调节。首先,在泡沫镍上生长出铱掺杂Ni V-LDH的样品,铱掺杂前后物相均为α-Ni（OH）₂相的片状结构,铱通过取代镍原子实现掺杂。当铱含量为14%时,Ni VIr-LDH表现出优异的性能,在OER和HER过电势值分别为203 m V和42 m V@10 m A cm^-2。在1.49 V电压下实现了10 m A cm^-2的电解水电流,远低于Pt/C–Ir/C电极对应电压（1.60 V）。对不同浓度的铱掺杂样品进行表征测试。铱含量较低时为α-Ni（OH）₂相和片状结构,但当铱含量大于19%,晶格结构被破坏转变为非晶。随着铱含量的增加,HER和OER性能,均表现出先上升后下降的趋势。计算表明,水分解、HER和OER分别在Ir、桥O和V原子上发生,以实现H^*/O^*中间体吸附能的独立调节。在Ir掺杂的Ni V-LDH中,掺杂的Ir离子起着三种作用:（i）Ir离子本身充当了水离解的催化位点;（ii）Ir离子存在降低了相邻桥氧的电荷密度,从而促进了桥氧原子的HER性能;（iii）Ir离子存在增加了V离子的电荷密度,从而提高了OER性能。因此,Ir掺杂的Ni V-LDH表现出卓越的全解水催化性能。更多还原

【Abstract】 Increasingly energy issues urgently require us to develop new green energy.Bifunctional electrocatalysts for both hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）are very crucial for converting water into clean fuel through overall water splitting.A bifunctional catalyst should contain catalytic sites that satisfies both HER and OER,has optimal adsorption energy for both HER and OER intermediates.Therefore,we aimed at designing separate catalytic sites for HER and OER on the surface of Ni-based LDH,so that the intermediates could be adsorbed by such sites and adjusted independently.First,Ir doped Ni V-LDH samples were prepared on Ni foam and the nanosheet array structure was obtained.Ir doped did not change theα-Ni（OH）₂ phase.The detailed characterizations showed that Ir atoms entered the lattice of Ni V-LDH by substituting Ni atoms.Ni VIr-LDH exhibits excellent performance when the Ir content is 14%.The resultant Ni VIr-LDH exhibited excellent performance with the OER and HER overpotential values of 203 m V@10 m A cm^-2 and 42 m V@10m A cm^-2,respectively.Thereby,the newly prepared Ni VIr-LDH catalyst achieved an overall water splitting current of 10 m A cm^-2 under an applied voltage of 1.49 V（as both anode and cathode）,which is much lower than that of the Pt/C–Ir/C couple(1.60V@10 m A cm^-2).Further,A series of Ir-doped LDH with different Ir contents in the Ni VIr-LDH material was prepared.The samples possessed the phase structure ofα-Ni（OH）₂and flake-like morphology.Once the Ir content exceeded 19%,the crystal structure was found to collapse and become morphous.Interestingly,both HER and OER performance first increased and then decreased with the increase in Ir contents.The result shows that water dissociation,HER and OER occur on Ir,bridge O and V atoms,respectively.Therfore,the H*and O*intermediates could be adsorbed by such sites and adjusted independently.The dopant Ir ions were found to play a triple role:（i）Ir ions serve as the catalytic sites for water dissociation;（ii）they reduce charge density on adjacent bridge oxygen,thus facilitating HER there;and（iii）finally they increase charge density on V ions,which in turn boosts OER.As a result,the novel catalyst achieves an ultralow applied voltage for overall water splitting.更多还原