Formic Acid Photo-Fuel Cells Consisting of TiO₂ Photoanode and Pt Cathode

Formic acid (HCOOH) has attracted much attention as a promising power source for portable electronic devices because of its ease of storage and transportation. Here we report that a simple HCOOH photo-fuel cell (PFC) consisting of mesoporous anatase TiO₂ photoanode and Pt cathode stably delivers a short-circuit photocurrent (J_sc) of 5.94 mA cm^-2 and an open-circuit voltage of 0.94 V under UV-light irradiation (light intensity, I=200 mW cm^-2). The incident photon-to-current conversion efficiency and Faradaic efficiency reach ~90 % and ~100 %, respectively. The excellent performances of this HCOOH PFC, designed based on the discovery that HCOOH provides a large photocurrent by current doubling even in the presence of O₂, not only solves the problem of conventional HCOOH FCs, but also achieves the performances far exceeding those of PFCs using biomass-derived organics reported so far.