| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016) | |
| Nanomaterials | Wednesday Sessions |
| Session NM-WeP |
| Session: | Nanomaterials Poster Session |
| Presenter: | Takahiro Inoue, Nagaoka University of Technology, Japan |
| Authors: | T. Inoue, Nagaoka University of Technology, Japan N. Saito, Nagaoka University of Technology, Japan M. Nishikawa, Nagaoka University of Technology, Japan |
| Correspondent: | Click to Email |
1. Introduction
H2 has received attention as a next-generation energy alternative to fossil fuels. In the past four decades, photocatalysts have payed attention to energy conversion materials for water splitting into H2 and O2. Recently, we have discovered that Mg-doped GaN has an ability to decompose water when depositing RuO2. [1] However, synthesized as-prepared Mg-doped GaN has an impurity phase such as MgO, and showed unstable activities at an initial stage of reaction, suggesting that an unstable layer soluble in water exists on as-prepared Mg-doped GaN. Therefore, it is necessary to remove them for improving the activity of photocatalytic water splitting. In this study, we investigated changes in photocatalytic activities by surface acid treatment.
2. Experimental
A precursor of Mg-doped GaN was obtained by co-precipitation method using Ga(NO3)3 and Mg(NO3)2 in alkaline solution. The precursor was heated at 1273 K for 15 h under NH3 atmosphere. The obtained Mg-doped GaN was treated by stirring in 0.1 M HCl solution. RuO2 was deposited by impregnation method in range from 1 to 5 wt% as a promoter. Photocatalytic water splitting was performed by closed gas circulation apparatus. A 300 W Xe lamp was used for photo-irradiation.
3. Results and discussion
As an impurity phase, an imperceptible peak for MgO was detected on as-prepared Mg-doped GaN. MgO was completely removed by surface acid treatment. For photocatalytic water splitting, RuO2-loaded as-prepared Mg-doped GaN evolved H2 and O2 with N2 at an initial stage of reaction, then N2 generation disappeared at the several runs of reaction, indicating that the outermost surface of the as-prepared Mg-doped GaN was dissolved in water by photo-irradiation. On the other hand, acid treatment gave stable and high activities for H2 and O2 evolutions compared to that of the as-prepared Mg-doped GaN without N2 production. The optimum amount of RuO2 on Mg-doped GaN changed from 3.5wt% to 2.0wt% after acid treatment.
4. Conclusions
Effects of acid treatment on Mg-doped GaN for photocatalytic water splitting were investigated. This work indicates that removal of surface impurity phase and unstable layer on Mg-doped GaN is promising approach.
References
[1] N. Arai, N. Saito, H. Nishiyama, Y. Inoue, K. Domen and K. Sato, Chem. Lett., 35, 796 (2006)