Electrochemical measurement is a simple analytical method suitable for an easy-to-use chemical sensor. Only small electrodes and a simple measuring device are required to perform a highly sensitive quantitative measurement. This paper reviews our researches for the development of electrochemical endotoxin sensors to show the potential of electrochemical sensors by introducing our studies on the development of detection principles as well as studies on the sensitivity enhancement.

Polymer electrolyte fuel cells (PEFCs) have increasing attractions as a power generator for nextgeneration vehicles and stationary cogeneration systems of electricity and heat. Wide spread of PEFCs is prevented by the limitation of Pt electrocatalysts. We try to develop metallocomplex-based anode catalysts to overcome some of the problems of the Pt catalysts. Among the metallocomplexes, Rh porphyrins exhibit high activity toward electrocatalytic oxidation of various fuel-related compounds such as CO, oxalic acid, sugars, alcohols, hydrazine derivatives, and borohydride. In this review, the development and analysis of Rh porphyrins-based electrocatalysts are summarized, and the benefits that are not observed in Pt catalysts are discussed.

In order to achieve the spontaneous hydrogen (H₂) evolution by using a photochemical reaction of fullerene (C₆₀), voltammetric behaviors of C₆₀ and its anion radical (C₆₀^•−) were investigated by means of voltammetry with an electron conductor separating oil-water (ECSOW) system. Nitrobenzene (NB) solutions and acidic aqueous solutions were used as the oil phase and the water (W) phase, respectively. In this work, two working electrodes with greatly different areas were used as the electron conductors, although two working electrodes with almost the same areas are usually used in voltammetry for the ECSOW system. As a result, we confirmed that the currents are controlled by the working electrode with a smaller area. Especially, when a microelectrode was used in the NB phase containing C₆₀ or C₆₀^•−, s-shaped voltammograms with limiting currents were obtained and thereby the diffusion coefficients of C₆₀ and C₆₀^•− were easily estimated to be 3.2×10⁻⁶ and 2.9×10⁻⁶ cm² s⁻¹, respectively. On the other hand, we could determine a criterion for the spontaneous H₂ evolution from the voltammogram measured for the ECSOW system, considering that the potential of the voltammogram corresponds to the electromotive force of the voltaic cell consisting of the NB and W phases. Based on this criterion, we supposed conditions for the spontaneous H2 evolution and successfully achieved the spontaneous H₂ evolution using a photovoltaic cell.