Direct biomass fuel cell (BMFC) for polymeric biomass with anode/catalyst device comprising a mesoporous n-semiconductor film/Co, Ni or Cu thin layer

Efficient direct biomass fuel cell (BMFC) anode/catalysts were successfully prepared that are comprised of [base FTO electrode/mesoporous n-TiO2 thin film/low cost metal thin layer], for which the low cost metal is Co, Ni or Cu, and FTO is a conductive glass electrode coated with an F-doped SnO2 thin layer. The metal thin layer was reductively electrodeposited onto a mesoporous 10 μm thick TiO2 thin film coated on an FTO. The anode/catalyst semiconductor (SC) devices in which the metal shows metallic luster were efficient for generating electrical power without any photoirradiation nor bias potentials by using polymeric biomass (BM) compounds such as starch, carboxy-methyl cellulose (CMC), and lignin–sulfonic acid in combination with an O2-reducing cathode the other side of which was exposed to ambient air. The TiO2/Cu device anode/catalyst generated with CMC fuel short circuit current Jsc of 740 μA cm−2, open circuit voltage Voc of 0.38 V, and fill factor FF of 0.25, leading to the maximum output power Wout of 70 μW cm−2. The TiO2/Ni device with starch gave Jsc 870 μA cm−2, Voc 0.33 V, FF 0.24 and Wout 69 μW cm−2. The TiO2/Cu with glucose gave Jsc 850 mA cm−2, Voc 0.69 V, and FF 0.25, attaining Wout 147 μW cm−2. It is important that the capability of electron utilization by the TiO2/Cu device with glucose reached more than 17e− among the theoretical 24e− (=71%) of one glucose molecule. It was strongly suggested that the interface between the TiO2/metal has both the Schottky-junction and Ohmic nature, which interpreted the multi-electron utilization of the biomass. It was proposed that, according to a simple calculation, the device has a potential to be used in a principal sustainable energy resource system.

Graphical abstractAnode/catalyst device was prepared by a mesoporous TiO2 thin film coated with a low cost metal (Co, Ni, or Cu) for efficient BMFC capable of generating electrical power directly from polymeric BM such as starch, cellulose and lignin.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► New semiconductor device was prepared by mesoporousTiO2 thin film and low cost metal layer as anode/catalyst of fuel cell. ► At the interface of the TiO2/metal device, both the Schottky-junction and Ohmic contact were found. ► Starch, cellulose and lignin generated electric power by the device with Cu, Ni, and Co metals using O2-reducing cathode. ► This direct biomass fuel cell has a potential to function as principal sustainable energy resource system in our society.