Understanding underlying processes in formic acid fuel cells.

A basic understanding of electrode structure and the characteristics of its components can be powerfully utilized in fuel cell applications such as direct formic acid fuel cell (DFAFC) system integration and HCOOH concentration controlled systems. There have been, thus, tremendous efforts made to elucidate theoretical aspects of electrochemical processes involving new anode catalysts and put them into practical effect on formic acid fuel cells. Herein, we highlight recent studies for better understanding of the underlying processes in DFAFC: (i) a systematic approach for developing cost-effective and stable anode catalysts and electrode structures that incorporate mass transport characteristics of HCOOH; (ii) a clear evaluation of the HCOOH crossover rate based on its physicochemical properties; and (iii) a theoretical assessment process of individual electrodes and related components during DFAFC operation using electrochemical impedance spectroscopy and a reversible hydrogen reference electrode, which can potentially detect subtle changes in the DFAFC mechanism and provide useful information pertaining to rate-limiting processes.