One-Compartment InGaN Nanowire Fuel Cell in the Light and Dark Operating Modes

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 (Jsc) 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.

Hydrogen peroxide photo-fuel cells

Hydrogen peroxide (H2O2) possesses both strong oxidizing and moderate reducing ability. Due to the unique chemical reactivity, one-compartmentalization of fuel cells is possible by using H2O2 as both the fuel and oxidant for fuel cells (H2O2-FC). To enhance the anode reaction (H2O2 → O2 + 2H+ + 2e-) of the H2O2-FC, a noble metal-free H2O2-photo fuel cell (PFC) has been newly developed for enhancing the conversion from chemical energy to electric energy with only emission of water and oxygen. The H2O2-photo fuel cells (PFC) take several significant advantages over the conventional hydrogen-oxygen fuel cells. With the realization of a solar-driven energy cycle with H2O2 as the key substance in mind, this Frontier article highlights the H2O2-PFCs. Firstly, the fundamentals of the H2O2-PFC are dealt with by treating the prototype using TiO2 as the photoanode. Then, recent progress in the H2O2-PFCs and an emerging application to self-powered biosensors are described. Finally, the conclusions are summarized with the future outlook.

InN/InGaN Quantum Dot Abiotic One-Compartment Glucose Photofuel Cell: Power Supply and Sensing

InN/InGaN quantum dots (QDs) are introduced as an efficient photoanode for a novel abiotic one-compartment photofuel cell (PFC) with a Pt cathode and glucose as a biofuel. Due to the high catalytic activity and selectivity of the InN/InGaN QDs toward oxidation reactions, the PFC operates without a membrane under physiologically mild conditions at medium to low glucose concentrations with a noble-metal-free photoanode. A relatively high short-circuit photocurrent density of 0.56 mA/cm² and a peak output power density of 0.22 mW/cm² are achieved under 1 sun illumination for a 0.1 M glucose concentration with optimized InN/InGaN QDs of the right size. The super-linear dependence of the short-circuit photocurrent density and the output power density as a function of the logarithmic glucose concentration makes the PFC well suited for sensing, covering the 4-6 mM range of glucose concentration in blood under normal conditions with good selectivity. No degradation of the PFC operation over time is observed.