(Keynote) Electrochemical Surface Science and Energy Conversion

Abstract

Electrochemical energy conversion processes play central roles in the future sustainable society based on renewable energy. To realize efficient electrochemical energy conversion processes, it is essential to understand the mechanisms of these processes by determining the geometric, electronic, and molecular structures of electrode, reactants, products, intermediates, and solvent at electrode/solution interfaces where the reactions are taking place in situ in real time. It is relatively easy to obtain such information in vacuum where electron beam techniques can be used but is difficult in solution as electron probe cannot be used. A wide range of in situ techniques have been developed in the course of the growth of electrochemical surface science in the last 25 years and we have contributed much to this development.1-3 Thanks to the development of electrochemical surface science, electrochemical studies are now routinely carried out in atomic/molecular resolution. Electrocatalysts are the key to improve the efficiencies of electrochemical energy conversion processes such as fuel cell reactions and water electrolysis and much effort has been made to design electrocatalysts for efficient electrochemical energy conversion processes rationally based on electrochemical surface science and theoretical analyses, which are significantly progressed recently. We have demonstrated how in situ, real time monitoring of electrochemical processes at electrode/electrolyte interfaces is critical to understand the reaction mechanism by showing some examples including 1. XAFS study on Pt-CeO2 electrocatalyst for oxygen reduction reaction (ORR),4 2. QCM study on ORR5 and the cathodic reaction of Li-O2 battery,6 and 3. the developments of ”real” in situ electrochemical XPS,7 gap-mode Raman,8 and double-resonance electrochemical SFG.9 In the presentation, I will describe some of the above and, in addition, our efforts to reduce the amount of Pt catalyst for photoelectrochemical hydrogen evolution at Si electrode by “confined molecular catalyst”,10 and our most recent activities of theory driven design and development of novel electrocatalysts based on boron nitride nanosheet, an insulator, for ORR11 and hydrogen evolution reaction12 are presented.