This article reports a brief review of electrochemical sensors and redox flow batteries based on nanostructured design strategy of solid electrode surface developed by our team, and then the practical applications of proposed techniques are introduced. The first content consists of surface modification techniques of solid electrode materials such as metal and carbon, which can control electro-catalytic activity and application for the determination various electroactive species. The second topic describes electrochemical sensors based on the batch injection coulometry by using our presented electrodes, which exhibited absolute determination of inorganic compounds in practical fields. Finally, we tried to develop vanadium redox flow batteries with high current density by using the electrochemical modified carbon felt electrodes.

Herein, we describe our recent studies on the molecular mechanism of adsorption-coupled electron transfer (ACET). ACET is ubiquitous and crucial in many important electrode reactions to generate irreversibly adsorbed products in electrodeposition and electrointercalation and reversibly adsorbed intermediates in electrocatalysis and photoelectrocatalysis. ACET reactions, however, are highly complex owing to the coexistence of concerted and non-concerted mechanisms. We established the theoretical framework of voltammetry to discriminate between the two mechanisms, which was demonstrated experimentally for the first time by using not cyclic voltammetry but transient voltammetry based on scanning electrochemical microscopy (SECM). The novel ACET mode of SECM will enable us to quantitatively understand the coupling between electron transfer and specific adsorption.

Formula to express the Frumkin effect is reconsidered from the viewpoint of easiness of understanding its physical meaning. Although it is usually expressed based on the potential difference, here it is expressed based on the concentration changes. There are two aims of this formula transformation: One is to treat the Red / Ox species equally in the expression. The other is to extend the applicability of the formula to the effects of concentration changes caused by other than pure electrostatic effects.

　ポーラログラフィスト，電気化学者にとっては，金属を電極とした固｜液界面，液（水銀）｜液界面の電気化学については非常になじみ深いが，固体が金属から電気伝導度が何桁も減少する半導体に置き換わると，その界面での電気化学は半導体物性に詳しくないこともあり，よくわからないという人が多いのかもしれない。一方で，光電気化学の分野では電極材料に半導体を使うことで光励起による電子-正孔のキャリア生成をつかって興味ある特性を示す多くのデバイスが提案されている。また，全固体電池の固体と固体の界面は半導体｜半導体界面，金属｜半導体界面であり，この界面に発生した電位差がリチウムイオンの伝導に大きな影響を与えることが示唆されている。[1]

　本シリーズでは，全文を4部にわけて報告する。Part Iでは半導体の基礎，Part IIでは半導体中のポアソンボルツマン式，Part IIIでは半導体｜電解質溶液の電気二重層，Part IVでは金属｜半導体界面の電気二重層，について記述する。

Again, the consideration of the electrical potential in the electrolyte, and especially the consideration of the difference of potential in electrolyte and electrode, involves the consideration of quantities of which we have no apparent means of physical measurement, while the difference of potential in “pieces of metal of the same kind attached to the electrodes” is exactly one of the things we can and do measure.