Metastable-phaseβ-Fe_(2)O_(3) photoanodes for solar water splitting with durability exceeding 100 h

光电催化分解水稳定性达100 h的亚稳相β-Fe_(2)O_(3)光阳极

Planar films of pure and Ti^(4+)-dopedβ-Fe_(2)O_(3)were prepared by a spray pyrolysis method.X-ray diffraction patterns and Raman spectra of the metastableβ-Fe_(2)O_(3)film showed that its thermal stability was significantly improved because of covalent bonds in the interfaces between the film and substrate,while only weak Van der Waals bonds existed at the interfaces within the particle-assembledβ-Fe_(2)O_(3)film prepared by electrophoretic deposition.The as-prepared planar films were thus able to withstand higher annealing temperature and stronger laser irradiation power in comparison with theβ-Fe_(2)O_(3)particle-assembly.Ti^(4+)doping was used to increase the concentration of carriers in the metastableβ-Fe_(2)O_(3)film.Compared with pureβ-Fe_(2)O_(3)photoanodes,the highest saturated photocurrent for water splitting over the Ti^(4+)-dopedβ-Fe_(2)O_(3)photoanode was increased by a factor of approximately three.Theβ-Fe_(2)O_(3)photoanode exhibited photochemical stability for water splitting for a duration exceeding 100 h,which indicates its important potential application in solar energy conversion.

利用半导体光电催化分解水制氢是将太阳能转化为化学能的有效途径之一,具有重要的科学意义和巨大的应用前景.铁基半导体具有光谱响应范围广、绿色环保和价格低廉等优点,是具应用前景的光阳极材料之一.在铁基半导体中,α-Fe_(2)O_(3)光阳极的光电催化性能已经被广泛报道,亚稳相氧化铁的光电催化性能尚未有深入研究.本课题组曾经报道用于光电催化分解水的亚稳相β-Fe_(2)O_(3)颗粒组装膜光阳极[Natl.Sci.Rev.,2020,7,1059-1067].β-Fe_(2)O_(3)光阳极的太阳能-氢能理论转化效率为20.9%,优于α-Fe_(2)O_(3)光阳极.β-Fe_(2)O_(3)的热稳定性和在长时间光电催化反应过程中的光化学稳定性是决定其应用前景的核心问题.本文报道了一种喷雾热裂解制备β-Fe_(2)O_(3)薄膜的方法.该方法提高了β-Fe_(2)O_(3)的热稳定性,从而提高了β-Fe_(2)O_(3)在长时间光电化学反应中的光电化学稳定性.与电泳沉积方法制备的β-Fe_(2)O_(3)颗粒组装膜相比,利用喷雾热裂解法制备的亚稳相β-Fe_(2)O_(3)薄膜的热稳定性得到显著增加.物相表征结果表明,经过相同的煅烧处理或者激光辐照后,电泳沉积方法制备的β-Fe_(2)O_(3)颗粒组装膜发生了明显相变;而由喷雾热裂解制备的β-Fe_(2)O_(3)平板膜依旧保持稳定,没有发生相变.β-Fe_(2)O_(3)薄膜与衬底之间存在较高的应力,与颗粒组装膜相比,平板膜在退火热处理与激光辐照下都表现出更好的稳定性.β-Fe_(2)O_(3)薄膜与衬底之间的应力增加了亚稳相β-Fe_(2)O_(3)的相变势垒,提高了β-Fe_(2)O_(3)的相变温度.通过引入Ti4+掺杂提高载流子浓度,改善载流子传输,使得β-Fe_(2)O_(3)光阳极的光电催化性能提升了3倍.结果表明,β-Fe_(2)O_(3)光阳极薄膜具有良好的光化学稳定性,其光电催化分解水性能在模拟太阳光条件下工作110 h后未出现明显的衰减.本文提出了一种增加亚稳相β-Fe_(2)O_(3)热稳定性的方法,β-Fe_(2)O_(3)光阳极具有较好的光化学稳定性,在光电催化方面具有较好的应用前景.