【作者】 王浩宇；

【导师】 谢腾峰；

【作者基本信息】 吉林大学 ， 物理化学， 2022， 硕士

【摘要】 随着工业社会的不断发展,温室效应以及能源危机成为了亟待解决的问题,人类急需寻找一种新的可持续能源。光电化学分解水制氢,将氢能源储存并加以利用,是一种解决目前能源问题的有效方法。目前,产氧半反应还是光电化学分解水反应的速控步骤,所以构筑高效、稳定的光阳极对整体光电化学分解水反应是具有决定性作用的。α-Fe₂O₃因其储量丰富,能带结构优异,理论光电流高（12.5m A/cm²）,被认为是光电化学水氧化反应中非常有前途的光阳极材料,但是由于其载流子浓度低、载流子迁移率慢等缺点导致严重的体相复合,以及缓慢的表面水氧化速率导致的表面复合等因素限制了α-Fe₂O₃光阳极的应用。缓慢的表面水氧化速率是一个极为重要的限制α-Fe₂O₃光阳极性能的因素,在α-Fe₂O₃表面负载高效稳定的OER电催化剂（作为助催化剂）是一种有希望改善α-Fe₂O₃表面水氧化速率的方法。过渡金属硫化物是一种优良的电催化水氧化材料,且目前很少应用在光电催化水氧化领域,因此在α-Fe₂O₃表面负载过渡金属硫化物助催化剂是一种很有前途的提高光阳极性能的方式。本论文利用Ti掺杂的方式对α-Fe₂O₃进行改性,并在表面负载过渡金属硫化物助催化剂,提升光生空穴的注入效率,增加光生电荷的分离效率,并且减小光生电荷在光阳极内部以及界面的传输阻力,极大的提升α-Fe₂O₃光阳极的光电流密度。此外,我们通过光电化学分析、稳态表面光电压技术、瞬态表面光电压技术、电化学阻抗谱等多种研究手段对复合光阳极的光生电荷行为进行了研究。本论文的研究内容主要分为以下两个部分:1.NiFeS_x助催化剂/Ti-Fe₂O₃光阳极的构筑以及光生电荷行为的研究:不同于传统的水热合成法,我们通过简单的一步原位电沉积法在Ti-Fe₂O₃光阳极上负载了NiFeS_x助催化剂。由于NiFeS_x助催化剂良好的电催化水氧化性能以及光阳极和助催化剂之间良好的界面接触,Ti-Fe₂O₃/NiFeS_x光阳极的光电流密度在1.23 V vs.RHE时可以达到3 m A/cm²,是单纯Ti-Fe₂O₃光阳极光电流密度的2.5倍,并且起始电位负移了170 m V。2.CoS-Z助催化剂/Ti-Fe₂O₃光阳极的构筑以及光生电荷行为的研究:为了进一步的提升Ti-Fe₂O₃光阳极的性能,我们逐步寻求更加高效的助催化剂材料,利用原位溶剂热刻蚀Zi F-67的方法在Ti-Fe₂O₃光阳极上负载了CoS-Z助催化剂。结果表明,CoS-Z助催化剂的负载增加了光生空穴的注入效率,增大了光生电荷的分离效率,并且减小了光生电荷的传输阻力,CoS-Z/Ti-Fe₂O₃光阳极的光电流密度在1.23 V vs.RHE时可以达到3.4 m A/cm²,是单纯Ti-Fe₂O₃光阳极光电流密度的2.8倍,并且起始电位负移了190 mV。更多还原

【Abstract】 With the continuous development of industrial society,the greenhouse effect and energy crisis have become urgent problems to be solved,people need to find a new sustainable energy source.Photo-electrochemical（PEC）water splitting to produce hydrogen energy is known as an efficient method to solve the energy problem.At the present stage,oxygen evolution reaction is also the speed step of PEC water splitting,therefore,actual PEC system design is mainly impeded by the efficiency of the photoanodes.Due to its abundant reserves,suitable band structure,the high theoretical photocurrent density（12.5 m A/cm²）,hematite（α-Fe₂O₃）has been considered to be an extremely promising photoanode in the PEC water oxidation reaction.However,due to its severe bulk recombination（low carrier concentration and mobility）and surface recombination（sluggish surface water oxidation rate）,the application ofα-Fe₂O₃photoanode is severely limited.Sluggish surface water oxidation rate is a significant rate-limiting factor,loading an appropriate OER electrocatalyst（regarded as a cocatalyst）on the surface ofα-Fe₂O₃ is known as a promising method to improve the surface water oxidation rate ofα-Fe₂O₃.Transition metal sulfide is a kind of excellent OER electrocatalyst and seldom used in the field of PEC water splitting.Therefore,loading transition metal sulfide cocatalyst onα-Fe₂O₃ is a promising method to improve PEC performance of the photoanode.In this paper,we modifyα-Fe₂O₃ photoanode by Ti doping and loading transition metal sulfide cocatalyst,the injection efficiency of photogenerated holes and the separation efficiency of photogenerated charge are improved,and the transmission resistance of photogenerated charge in the photoanode and the interface is reduced,the photocurrent density ofα-Fe₂O₃photoanode is improved observably.In addition,in order to analyze the behavior of photogenerated charges and the true effect of cocatalyst for the enhanced PEC performance ofα-Fe₂O₃ photoanode,we obtain surface photovoltage spectroscopy（SPV）,transient photovoltage（TPV）technique and photoelectrochemical impedance spectroscopy（PEIS）.The research content of this paper is mainly divided into the following two parts:1.Construction of NiFeS_x cocatalyst/Ti-Fe₂O₃ photoanode and study of photogenerated charge behavior:Different from the traditional hydrothermal synthesis method,we synthesize NiFeS_x modified Ti-Fe₂O₃ photoanode through simple one-step in-situ electrodeposition.Due to the excellent electrocatalytic performance of NiFeS_xand the well interfacial contact between photoanode and cocatalyst,the resulting NiFeS_x/Ti-Fe₂O₃ photoanode shows an excellent photocurrent density of 3 m A/cm² at1.23 V vs.RHE,which is 2.5 times larger than the photocurrent of pure Ti-Fe₂O₃photoanode and a 170 m V water oxidation onset potential shift compared with pure Ti-Fe₂O₃.2.Construction of CoS-Z cocatalyst/Ti-Fe₂O₃ photoanode and study of photogenerated charge behavior:We are gradually seeking more efficient cocatalyst materials to improve the PEC performance of Ti-Fe₂O₃ photoanode furtherer.We synthesize CoS-Z modified Ti-Fe₂O₃ photoanode through in-situ solvothermal method etching Zi F-67.The results show that after loading the CoS-Z cocatalyst,the injection efficiency and separation efficiency of photogenerated holes of photoanode are improved,the transmission resistance of photogenerated charge is reduced.the CoS-Z/Ti-Fe₂O₃ photoanode shows an excellent photocurrent density of 3.4 m A/cm² at 1.23V vs.RHE,which is 2.8 times larger than the photocurrent of pure Ti-Fe₂O₃ photoanode and a 190 m V water oxidation onset potential shift compared with pure Ti-Fe₂O₃.更多还原