Recently, a new process has been made to significantly improve the photocatalytic water splitting efficiency of iron oxide in study of micro-nano-structured Iron oxide materials, iron oxide doping and heterojunction, by a team including ISSP researchers, led by Dr. Chang Hui YE.
In the environmental crisis intensified today, it is necessary to develop clean and renewable energy. Compared to solar energy and nuclear energy, hydrogenic energy has no damage on the environment whose source and product is water. Moreover, the semiconductor photocatalytic splitting water has greater prospects than the traditional way of producing hydrogen by electrolysis water. The optical band gap of Iron Oxide is so right that it can make full use of the visible light, which leads to the theory efficiency up to 15%.
The team prepared micro-nano-structured hematite electrodes in an acid solution using a simple hydrothermal method and enhanced conversion efficiency by doping Ti ions. The photocurrent increases for enhanced electrical conductivity. Further enhanced photocurrent is achieved for Fe2O3:Ti/ZnFe2O4 heterojunction electrodes. Cyclic voltammograms combined with optical absorbance examinations demonstrate that the conduction and valence band edges of ZnFe2O4 shift from those of Ti doped Fe2O3 to the negative direction, which facilitates the efficient separation of electron−hole pairs at the Fe2O3:Ti/ZnFe2O4 interface. Further, a higher concentration of Ti ions are incorporated into hydrothermally grown Ti-doped micro-nano-structured hematite films by an in situ solid-state reaction method. These findings demonstrate that the in situ solid-state reaction is an effective method to increase the doping level of Ti ions in hematite films with the retention of the micro-nanostructure of the films and enhance the photocurrent.
The relevant results have been published in ACS Applied Materials & Interfaces (ACS Appl. Mater. Interfaces 4, 4428-4433, 2012 and ACS Appl. Mater. Interfaces 5, 1310-1316, 2013). This work was supported by National Basic Research Program of China (973 Program, Grant No. 2011CB302103), National Natural Science Foundation of China (Grant Nos. 11074255 and 11274308), and the Hundred Talent Program of the Chinese Academy of Sciences.
Figure 1: Micro-nano-structured hematite films producing by hydrothermal method (left); the structure schematic of Fe2O3:Ti/ZnFe2O4 heterojunction (right)
Figure 2: J-V of the samples before and after in situ solid-state reaction