Department of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo Bunkyoku, Tokyo, 113-8656, Japan.
Dalton Trans. 2009 Dec 7(45):10055-62. doi: 10.1039/b910318j. Epub 2009 Aug 11.
Overall water splitting to form hydrogen and oxygen over a heterogeneous photocatalyst using solar energy is a promising process for clean and renewable hydrogen production on a large-scale. The ZnGeN2-ZnO solid solution photocatalyst shows photocatalytic activity under visible irradiation. This paper deals with results of photocatalytic reactions over the (Zn(1+x)Ge)(N2O(x)) photocatalyst for overall water splitting. The photocatalyst shows high rates for overall water splitting under visible irradiation, with notable deactivation with time. This study focuses on measuring rates for H2 and O2 evolution to elucidate the cause of the deactivation. Our results showed negligible changes in the structure and the composition of the photocatalyst after the photocatalytic reaction, and thus the changes undetectable by the techniques employed should be the cause of deactivation. This paper also discusses two strategies to improve the photocatalytic activity: metal doping in the oxynitride formulation and post-calcination after nitridation. Several characterization carried out in this study led us to conclude, at the current point, that the improvement of photocatalytic activity is ascribed to the reduction in the number of defects in the photocatalyst materials.
利用太阳能在多相光催化剂上整体分解水以形成氢气和氧气是一种有前途的大规模清洁可再生制氢方法。ZnGeN2-ZnO 固溶体光催化剂在可见光照射下具有光催化活性。本文介绍了（Zn(1+x)Ge）(N2O(x))光催化剂用于整体水分解的光催化反应结果。该光催化剂在可见光照射下表现出高的整体水分解速率，但随着时间的推移会显著失活。本研究重点测量 H2 和 O2 生成的速率，以阐明失活的原因。我们的结果表明，光催化反应后光催化剂的结构和组成没有明显变化，因此，应该是所采用技术无法检测到的变化导致了失活。本文还讨论了两种提高光催化活性的策略：在氧氮化物配方中进行金属掺杂和氮化后进行煅烧后处理。本研究进行的几项表征使我们得出结论，在目前的阶段，光催化活性的提高归因于光催化剂材料中缺陷数量的减少。
