Functional principle of the synergistic effect of co-loaded Co-Pi and FeOOH on Fe2O3 photoanodes for photoelectrochemical water oxidation  

Co-Pi与FeOOH对Fe2O3光阳极用于光电化学氧化的协同作用原理

作　　者：Jingran Xiao Longlong Fan Zhongliang Huang Jun Zhong Feigang Zhao Kaiji Xu Shu-Feng Zhou Guowu Zhan 肖静冉;范龙龙;黄忠亮;钟俊;赵飞刚;徐凯吉;周树锋;詹国武(华侨大学化工学院,福建厦门361021)

机构地区：[1]College of Chemical Engineering,Huaqiao University,Xiamen 361021,Fujian,China

出　　处：《Chinese Journal of Catalysis》2020年第11期1761-1771,共11页催化学报（英文）

基　　金：华侨大学科研启动基金(605-50Y19013).

摘　　要：The establishment of multi-component catalytic systems on Fe2O3 photoanodes presents considerable potential for significantly enhancing the performance of photoelectrochemical water splitting systems. In this study, we hydrothermally synthesized a Fe2O3 photoanode. In addition, d-Fe OOH synthesized via dip-coating and hydrothermally prepared h-FeOOH were used as cocatalysts and their synergistic combinations with cobalt phosphate(Co-Pi) were investigated. The synergy between h-FeOOH and Co-Pi was remarkable, whereas that between d-Fe OOH and Co-Pi was negligible. For example, the onset potentials of the Co-Pi/h-FeOOH and Co-Pi/d-FeOOH dual catalysts, were cathodically shifted by 270 and 170 m V, respectively. Moreover, the photocurrent density of the Co-Pi/h-FeOOH/Fe2O3 anode was significantly higher than that of the Co-Pi/d-FeOOH/Fe2O3 one. The synergistic effect of Co-Pi and h-FeOOH could be attributed to the significantly inhibited recombination of surface charges owing to the formation of a p-n junction between β-FeOOH and Fe2O3 and the large contact area between the granular h-FeOOH and Co-Pi. However, the thin amorphous FeOOH layer of the Co-Pi/d-FeOOH/Fe2O3 anode acted as a hole-transfer medium, and weakly promoted the kinetics of the charge transfer process.利用太阳能光电解水反应制氢为解决能源危机和环境问题提供了一条途径,是目前研究的热点方向.目前研究较多的一种光阳极材料是α-Fe2O3,其禁带宽度窄(2.0–2.2 e V),水稳定性高且天然丰度高.但是, Fe2O3的导带位置低于水还原电极电势,而且Fe2O3表面存在大量的表面态,造成费米能级"钉扎"效应,使其开启电压高达0.8–1.0 V.大量研究表明,在Fe2O3表面负载水氧化助催化剂可以有效降低其开启电压,但多数研究集中于采用单一催化剂,提升效率有限.已有采用双助催化剂提升Fe2O3光电效率的研究报道,但是对其协同作用原理解释不清晰.更重要的是,双助催化剂的性质选择没有一致性规律,这给复合型助催化剂的研究带来了不确定性.本文研究了Co-Pi与FeOOH对Fe2O3光阳极的协同作用原理.分别通过浸涂法和水热法制备了两种FeOOH,在得到的FeOOH/Fe2O3光阳极表面通过光电化学方法制备Co–Pi薄膜.采用电化学阻抗谱表征和电化学动力学分析,重点研究两种FeOOH与Co-Pi形成复合助催化剂对Fe2O3光阳极开启电压的协同作用原理及差异,旨在指导双助催化剂的复合方案.X射线衍射(XRD)和高分辨透射电镜(HRTEM)表征结果表明,浸涂法得到的FeOOH为无定形薄膜(记为d-FeOOH),水热法得到的FeOOH为颗粒状的结晶β-FeOOH (记为h-FeOOH).采用X射线光电子能谱(XPS)和扫描电镜(SEM)元素面扫证明了Co-Pi的成功负载.H-FeOOH/Fe2O3比d-FeOOH/Fe2O3具有更高的电化学活性表面积.从极化曲线可以看出,Co-Pi/h-FeOOH双助催化剂使Fe2O3的开启电压降低了270 m V,而Co-Pi/d-FeOOH仅能使其降低170 m V,并且Co-Pi/h-FeOOH/Fe2O3的光电流有明显提升.因此, Co-Pi与h-FeOOH产生了显著的协同作用,但是与d-FeOOH的协同作用很弱.莫特-肖特基(Mott-Schottky)和紫外光电子能谱(UPS)证明h-FeOOH与Fe2O3之间形成了P-N结,提升了载流子浓度,增强了电极导电性.开路电压(OCP)测�

关 键 词：FE2O3 Synergistic effect Onset potential PHOTOANODE Water splitting 

分 类 号：TQ116.2[化学工程—无机化工] TQ426