Current status of research on catalysts related to supply chain of hydrogen such as hydrogen production, hydrogen carrier, and fuel cell electrocatalyst is introduced. Both the water-splitting to hydrogen and CO2 reduction by photocatalysts have attracted much attention as one of the uses of renewable energy. Platinum is well known as active electrocatalysts for ORR (oxygen reduction reaction), however, the reduction and/or replacement of platinum to base metals is strongly desired. Recently, new types of Ru-based catalysts for ammonia synthesis and decomposition have been developed. The reaction conditions of Ru-based catalysts is much milder than that used for conventional Fe-K catalysts. Catalytic reactions are expected to play an important role in fabrication and utilization of several kinds of energy carriers such as methane, methanol, ammonia, and organic chemical hydrides.
We are improving hydrogen production catalysts to reduce cost of natural gas fueled fuel cell systems. As a desulfurization catalysts, we developed a direct decomposition desulfurization catalyst which is neither adsorption nor hydrogeneration. As a steam reforming catalyst, a catalyst compeonent which does not deteriorate even if a sulfur compound remains in the gas was found. As a CO removal catalyst, a selective CO methanation catalyst with excellent activity and selectivity was developed. Combining these technologies can greatly simplify the current reforming process.
A structured reaction system, which was constructed by monolithic honeycomb-type catalysts, has excellent thermal conductivity and quick response to load fluctuations. This article mentioned such a structured reaction system for production and utilization of hydrogen. For processing the methane reforming, a nickel-based honeycomb-type catalyst was prepared using a combination technique of sol-gel method and electroless plating. The prepared honeycomb-type catalyst indicated high and stable performance for steam reforming and dry reforming of methane, comparing with commercial catalysts. The excellent heat-exchanging ability of the structured system produced high exergy efficiency by combining with an exothermic reaction like as methane combustion. For utilization of hydrogen, this article also introduced the methanation system to reduce carbon dioxide and to make energy resource by using the structured reaction concept.
Carbon supported Pt shell-Pd core structured catalyst (Pt/Pd/C) was successfully synthesized via a modified Cu under potential deposition/Pt displacement method. It was found that the Pd core preferentially dissolved out and the Pt shell was rearranged and thickened by a potential cycling performed at 80°C, which enhanced activity of the catalyst for oxygen reduction reaction (ORR). We developed Cu-O2 chemical treatment method which mimics the potential cycling and is suitable for a mass production of highly active Pt/Pd/C catalyst. Furthermore, SiO2 and carbon protective coatings were formed to mitigate agglomeration of the catalyst nanoparticles and improve durability of the catalyst. The highly activated and durable Pt/Pd/C catalyst could be a promising candidate for decrease of Pt usage for polymer electrolyte fuel cells (PEFCs).
One major problem for polymer electrolyte membrane fuel cells in commercial applications is the cost and scarcity of platinum, which is used as the cathode catalyst, and the development of Pt-free cathode catalysts is strongly desired. We have explored the synthesis of a carbon-based catalyst from polyimide nano-particles. Polyimide is a thermo resistive polymer and the morphology of precursor can be retained even after the carbonization; therefore, finer morphology can be expected. The obtained carbon-based catalyst shows a quite promising fuel cell performance. This articles focuses on the recent progress on the material synthesis and fuel cell performance.
Supported metal catalysts for synthetic methane production by hydrogenation of CO2 was reviewed. Some of recent researches and developments in applications of CO2 methantation to efficient utilization of renewable energy resources were introduced as well. It was highlighted that CO2 methanation was old but still played an important role in energy storage and transport, especially when renewable energy resources were concerned.
A large-scale and cost-effective production of hydrogen by thermochemical water splitting cycles using solar as well as nuclear heat sources is of great importance. The iodine-sulfur cycle consisting of the decomposition of H2SO4 and HI is a promising candidate. Both reactions require novel catalytic materials having not only high activities but also tolerance to corrosive environments, which severely damage most conventional materials. This short review article describes the current status of catalyst development for these reactions.
Molecular hydrogen (H2) has been accepted to be an inert and nonfunctional molecule in our body. Mammalian cells cannot metabolize H2 because of the lack of hydrogenase enzymes. We have overturned this concept by demonstrating that H2 reacts with strong oxidants such as hydroxyl radicals in cells, and proposed its potential for preventive and therapeutic applications. There are several methods to ingest or consume H2; inhaling H2 gas, drinking H2-dissolved water (H2-water), injecting H2-dissolved saline (H2-saline), or taking an H2 bath. H2 has a number of advantages exhibiting extensive effects: H2 rapidly diffuses into tissues and cells, and it is mild enough neither to disturb metabolic redox reactions nor to affect signaling reactive oxygen species; therefore, there should be no or little adverse effects of H2. The numerous publications on its biological and medical benefits revealed that H2 functions as an anti-inflammatory and anti-apoptotic, and stimulates energy metabolism by regulating the gene expressions. In addition to growing evidence obtained by model animal experiments, extensive clinical studies were performed or are under investigation. Owing to its great efficacy and lack of adverse effects, H2 has promising potential for clinical use against many diseases.