Control in Surface Atomic Structure of Heterogeneous Catalysts: Fundamental Understanding of Surface Reaction on Solid Surface
Heterogeneous reaction occurs at the interface of liquid/gas medium and solid catalyst. The property of solid surface is very important to control activity, selectivity, and long-term stability of the catalytic reaction. The geometry and electronic structure of the surface affects the catalytic property. The surface can be modulated in a rational way by nano-structure control, and the well-defined nano-catalysts can be used to elucidate the fundamental principals of heterogeneous reactions.
 Pt Minimization
Platinum (Pt) is a king of the catalysts. It is the most widely used material for various catalytic reactions, such as exhaust treatment or hydrogen fuel cells. However, the high cost and rarity of Pt metal often hinder market expansion. The form of 3~5 nm sized Pt nanoparticles are typically used as catalysts, with more than a half of Pt metal atoms occluded inside the nanoparticles. The Pt use can be minimized by exposing all the Pt metal atoms at the surface of supports. Additionally, the control of Pt atom arrangement at the surface, e.g. isolated versus neighbored, can modulate the selectivity while maximizing the activity.
 Gas-Phase Reactions: Air Purification, Methane Conversion, Reforming
CO, hydrocarbons, NOx, SOx species are formed from various types of vehicles. Especially, as internal combustion engine has been advanced, the temperature in the after-treatment system becomes lower, obscuring the catalytic conversion. Much better catalysts are needed for gasoline hybrid cars. The cheap and durable catalysts are also highly required for motorcycles or indoor air cleaner. Additionally, we are developing novel catalysts for direct methane conversion or hydrogen production via reforming.
 Electrochemical Reactions: H2 Fuel Cells, Water Electrolysis, CO2 Conversion
Electrocatalysts for ORR, OER, HOR, HER, CO2RR typically have the form of nanoparticles deposited on conducting supports. We are developing these electrocatalysts, particularly focusing on applying them into membrane-electrode-assembly (MEA) system. We are trying to minimize the use of precious metals or develop non-precious metal catalysts. Photo-assisted electrochemical reaction system is also studied.