Water electrolysis is one of the most significant technologies for the utilization of renewable energy. To meet the huge demand for green hydrogen, there is a strong need for innovative technologies to increase the efficiency of water electrolysis and to reduce the associated cost. This contribution summarizes the fundamental aspects of water electrolysis under near neutral pH electrolyte conditions, with the expectation that many elements and substances will be available that are not in extremely acidic or alkaline electrolytes. For efficient water electrolysis at near neutral pH, maximizing buffer substance flux, or “electrolyte engineering,” is the key to improving both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Buffer substance can either act as proton donors/acceptors or participate in electrocatalytic reactions as direct reactants, depending on the buffer species and operating current density. A dense buffer electrolyte can also reduce solution resistance. Hydrophilized porous glass sheets were demonstrated as a gas separator producing 99.9% H₂ at 100 mA cm⁻². Recent advances in electrolyte engineering, along with “nano-engineering” to increase the surface area of the electrodes, have made it possible to achieve OER performance at near neutral pH that is comparable to alkaline pH with abundant elements. Finally, the future direction of water electrolysis research will be prospected.

Yamanashi Prefecture is developing P2G system technology that absorbs electricity from renewable energy at the Komekurayama Electric Power Storage Technology Site. We will present the outline of the empirical research that producing hydrogen from a 1.5 MW PEM water electrolyzer and using inside prefecture.

Recently, the hydrogen production using renewable energy has been attracting strong attention. However, the basic technology for the evaluation of element in the water electrolyzer has not been established at present. In this study, we developed a standard cell for the element evaluation of the water electrolysis. In this report, we introduce the feature of the developed cell. This standard cell has the two excellent features. The first function is the precise pressure control structure to the electrode area. The precise pressure setting for the electrode area is extremely important for the performance of electrolysis because the shortage of pressure to the electrode area occurs not only the increase of contact resistance but also the influence of the effective utilization ration of catalyst or the mass transfer resistance in some cases. The second function is the precise measurement for the polarization by using two reference electrodes. The newly developed evaluation method can measure the anode and cathode polarization and mass transfer overpotential. These functions can accelerate the development of electrolyzer compositions by optimizing the structure. We except that this standard cell will be used as a powerful tool to improve the fundamental technology of water electrolysis.

Hydrogen is an important media to convert unstable renewable energy to stable and transportable energy substances. Water electrolysis is a major technology to produce low-cost large amounts of hydrogen. Solid alkaline water electrolysis using an anion exchange membrane has recently attracted significant attention as an efficient hydrogen production system without using noble metals in rapid response to fluctuating and unstable electric power generated from solar and wind power energies. The development of this system has been however long limited due to the lack of stable membranes in alkaline conditions. In addition, not only using high-performance membrane and catalyst materials, but also membrane–electrode assemblies (MEAs) should be taken into account for obtaining high-performance and durable water electrolysis cell system. Based on the systematic material design, we first clarified the degradation mechanism of conventional membranes and succeeded in developing highly durable anion exchange membranes under high temperature and alkaline conditions. Then, high-performance and durable MEAs using our developed membranes have been demonstrated at the water electrolysis operations not only in alkaline solutions but also in pure water. These achievements are breakthrough technologies that will greatly advance the research of solid alkaline water electrolysis for realizing a global hydrogen energy society.

Methanation is a rational method that allows natural gas and city gas users to smoothly promote carbon-neutralization at low cost while utilizing their existing equipment and facilities. SOEC methanation technology (high temperature electrolysis and gas synthesis technology) is expected to be an innovative technology that can synthesize non-fossil fuels such as green methane using non-fossil electricity with extremely high energy conversion efficiency that exceeds that of hydrogen production by water electrolysis. In this paper, the outline and potential of this technology, our efforts, and future prospects will be introduced.

Research and Development on hydrogen energy systems including water electrolysis, methylcyclohexane (MCH) production, ammonia synthesis, and/or, power generation by internal combustion engines have been performed in Fukushima Renewable Energy Institute, AIST (FREA). Hydrogen production by water electrolysis is one of the most important technology to store and transport a large amount of energy, and, to use unstable electricity generated by renewable sources. We investigated an alkaline water electrolyzer performance and characteristics under fluctuating current conditions. The electrolyzer is connected to hydrogenation reactors to produce MCH, which is one of a liquid organic hydrogen carrier (LOHC). A control method for fluctuating operation was developed and successfully applied to the MCH production system. For further development of integrated system and its control, dynamic simulation technologies are effective. We have developed a dynamic simulator of alkaline water electrolyzer considering temperature change in fluctuating operation.

In order to realize the life support system under the closed environment in space, revitalization of water is essential. Water is not only used for drinking but should also be electrolyzed to generate oxygen for the human activity. Then, the carbon dioxide is generated by the metabolic reaction, which can be reacted with excess hydrogen generated together with oxygen. This is one of the current applicable processes for the revitalization of water in space. During the reduction process of carbon dioxide, methane is also generated accompanied with water. Since the methane is the fundamental compound of the natural gas, the space oriented technique for the life support system has the potential to contribute to the carbon neutral society.

Here, we discuss the possibility of the hybrid device combining the water electolyzer with methanation process targeting the dual use for the space and the terrestrial applications.

The Government of Japan announced the “6th Strategic Energy Plan” in October 2021. This paper introduces the outline of the “6th Strategic Energy Plan” and the “Energy Supply and Demand Outlook for 2030” announced by the Ministry of Economy, Trade and Industry as related materials. The position of hydrogen in the “6th Strategic Energy Plan” is also described.