Yutaka Sasaki

Highly Active GaN‐Stabilized Ta3N5 Thin‐Film Photoanode for Solar Water Oxidation

Ta3 N5 is a very promising photocatalyst for solar water splitting because of its wide spectrum solar energy utilization up to 600u2005nm and suitable energy band position straddling the water splitting redox reactions. However, its development has long been impeded by poor compatibility with electrolytes. Herein, we demonstrate a simple sputtering-nitridation process to fabricate high-performance Ta3 N5 film photoanodes owing to successful synthesis of the vital TaOδ precursors. An effective GaN coating strategy is developed to remarkably stabilize Ta3 N5 by forming a crystalline nitride-on-nitride structure with an improved nitride/electrolyte interface. A stable, high photocurrent density of 8u2005mAu2009cm-2 was obtained with a CoPi/GaN/Ta3 N5 photoanode at 1.2u2005VRHE under simulated sunlight, with O2 and H2 generated at a Faraday efficiency of unity over 12u2005h. Our vapor-phase deposition method can be used to fabricate high-performance (oxy)nitrides for practical photoelectrochemical applications.

Balancing control method of a microgrid with intermittent renewable energy generators and small battery storage

A cooperative control system for gas engine generators and a lead-acid battery in a microgrid was developed. The control system enables a microgrid system to balance the electric power demand and supply and to simultaneously control the state of charge (SOC) of the battery. To evaluate this control system, we simulated its performance in balancing the control of an experimental microgrid facility with two reciprocating engine generators for a day in which large fluctuation in PV and wind turbine output was observed. Based on the simulation, the rated power ratio of renewable energy installed in the microgrid can be increased beyond 50%, and simultaneously the minimum feasible capacity of the battery can be reduced to the capacity which is enough to charge the rated output of the intermittent renewable energy for 15 minutes.

Automatic diagnosis of plant disease - Spectral reflectance of healthy and diseased leaves

Abstract Accurate diagnosis of plant diseases is needed to minimize the use of agricultural chemicals. Because it must be designed for laborsaving and work efficiency in the actual management system, this automation is a critical problem for the future. The final objective of this project is the construction of an automated system to diagnose plant disease. This article reports on the spectral reflectance characteristics of healthy and diseased leaves. The results obtained were as follows: 1. A wavelength that distinguishes between two categories of leaves (healthy and diseased) was identified using the Distinction Index (D.I.). 2. The difference between near ultraviolet information and near infra-red information gave the largest D.I., and the ratio of red wavelength centered at 660 nm to violet wavelength centered at 400 nm gave the largest D.I. in the visible range.

Towards zero bias photoelectrochemical water splitting: onset potential improvement on a Mg:GaN modified-Ta3N5 photoanode

Tantalum nitride (Ta3N5) based photoanodes were overlaid with magnesium-doped gallium nitride (Mg:GaN) thin films by using a plasma-enhanced chemical vapor deposition (PCVD) technique, and subjected to photoelectrochemical activity tests, aiming for a negative shift of onset potential for O2 evolution. A remarkable negative shift of the onset potential was observed after annealing Mg:GaN in N2 gas, reaching 0 V vs. RHE, despite a lower photocurrent than that on bare Ta3N5. Mg:GaN annealed in NH3 exhibited an improvement of the photocurrent. A detailed study of the photoelectrochemical performance for various samples and a thorough characterization have revealed the effects of N2/NH3 post annealing on Mg activation/Ta3N5 damage recovery, controlling the onset potential shift and the current density improvement. N2 post annealing shifted the onset potential to 0 V vs. RHE but decreased the current density. On the other hand, NH3 post annealing slightly shifted the onset potential and increased the current density largely. Despite the current density loss, this onset potential shift unlocks the prospect of unassisted photoelectrochemical water splitting on Ta3N5.

Presenting a Model for the Revival of Rural Communities in Japan’s Disaster Zones

During our research for the Great East Japan Earthquake Recovery Assistance Project, we focused on the city of Iwanuma in Miyagi Prefecture, where we held workshops with farmers to discuss how the revival of agriculture in the area should proceed. The feedback from these workshops was subsequently reflected in our revival plan. However, scientific data on how the ground had been altered by the earthquake and tsunami was also required to hasten the area’s reconstruction and revival. To this end, we used a three-dimensional (3-D) laser measurement system with MMS (Mobile Mapping System) to reveal the changes in the topography of the survey district. Our results suggest that the MMS system can be applied across a diverse range of fields related to community development, such as improving emergency evacuation routes and road infrastructure, devising town planning models, or for agricultural production forecasting. In future, we plan to survey a wider area, and to use our findings as a baseline ground map for actual restoration work as we conduct further research into how these baseline data can be applied to community development.