The micro polymer-electrolyte fuel cell (PEFC) uses hydrogen gas as a fuel and is apparently small enough to directly fit in a mobile phone. The new micro polymer-electrolyte based fuel cell competes with the current direct-methanol fuel cell (DMFC) development.
NTT says DMFCs have two issues: They generate CO2 and it is difficult to miniturize the fuel cell, while still generate enough power for running a mobile phone.
The PEFCs do not generate CO2 and the current PEFC prototype has a compact size (external dimensions: 42*80*13 mm; weight: 104 g), which makes it suitable for directly fitting into a mobile phone, and enables a talk time of nine hours.
More details in NTT press-release.
Past Fuel Cell News:
KDDI to develop Fuel Cell Mobile Phone
Toshiba Tiny Fuel Cell for Wearable Devices
Nokia Fuel Cell Bluetooth Headset