Department of Applied Chemistry, Graduate School of Engineering , Hiroshima University , 1-4-1 Kagamiyama , Higashi-Hiroshima , Hiroshima 739-8527 , Japan.
Graduate School of Human and Environmental Studies , Kyoto University , Yoshida Nihonmatsu-cho, Sakyo-ku, Kyoto 606-8501 , Japan.
Inorg Chem. 2018 Nov 5;57(21):13953-13962. doi: 10.1021/acs.inorgchem.8b02498. Epub 2018 Oct 8.
A solid solution of GaN and ZnO (GaN:ZnO) is promising as a photocatalyst for visible-light-driven overall water splitting to produce H. However, several obstacles still exist in the conventional preparation procedure of GaN:ZnO. For example, the atomic distributions of Zn and Ga are nonuniform in GaN:ZnO when a mixture of the metal oxides, i.e. GaO and ZnO, is used as a precursor. In addition, GaN:ZnO is generally prepared under a harmful NH flow for long durations at high temperatures. Here, a facile synthesis of GaN:ZnO with homogeneous atomic composition via a simple and safe procedure is reported. A layered double hydroxide (LDH) containing Zn and Ga was used to increase the uniformity of the atomic distributions of Zn and Ga in GaN:ZnO. We employed urea as a nitriding agent instead of gaseous NH to increase the safety of the reaction. Through the optimization of reaction conditions such as heat treatment temperature and content of urea, single-phase GaN:ZnO was successfully obtained. In addition, the nitridation mechanism using urea was investigated in detail. NH released from the thermal decomposition of urea did not directly nitride the LDH precursor. X-ray absorption and infrared spectroscopies revealed that Zn(CN)-like intermediate species were generated at the middle temperature range and Ga-N bonds formed at high temperature along with dissociation of CO and CO.
GaN 和 ZnO 的固溶体（GaN:ZnO）有望成为可见光驱动整体水分解制氢的光催化剂。然而，在 GaN:ZnO 的常规制备过程中仍然存在一些障碍。例如，当使用金属氧化物混合物（即 GaO 和 ZnO）作为前体时，GaN:ZnO 中 Zn 和 Ga 的原子分布不均匀。此外，GaN:ZnO 通常在高温下长时间在有害的 NH 流下制备。在这里，报道了一种通过简单安全的方法制备具有均匀原子组成的 GaN:ZnO 的简便方法。使用含有 Zn 和 Ga 的层状氢氧化物 (LDH) 来提高 GaN:ZnO 中 Zn 和 Ga 原子分布的均匀性。我们使用尿素作为氮源而不是气态 NH，以提高反应的安全性。通过优化热处理温度和尿素含量等反应条件，成功获得了单相 GaN:ZnO。此外，详细研究了使用尿素的氮化机制。尿素热分解释放的 NH 并没有直接氮化 LDH 前体。X 射线吸收和红外光谱表明，在中温范围内生成了 Zn(CN)-样的中间物种，并且随着 CO 和 CO 的解离，Ga-N 键在高温下形成。
