An engineered microbe transforms carbon dioxide into a prospective liquid fuel in tandem with electrical power rather than light.

Abstract

The fabrication of nanostructured electrodes for enzymatic glucose-oxygen biofuel cells is reported. The electrodes are based on enzyme encapsulation in sol-gel silica matrices and incorporate carbon nanotubes within the matrix to provide enhanced electronic conduction. The silica matrix is designed to be sufficiently porous that both glucose and oxygen have access to the enzymes and yet provides a protective cage for immobilizing the biomolecules without affecting biological function. Voltammetry experiments indicate that the effect of the silica matrix on mediator diffusion is minimal, although for one mediator, 2,2Ј-azino-bis͑3-ethylbenzothiazoline-6-sulfonic acid͒ diammonium salt, chemical modification of the solvent phase with polyethylene glycol is necessary. The polyethylene glycol addition also results in a more uniform dispersion of the carbon nanotubes. The enzymes maintain their biocatalytic activity in the sol-gel matrix. A glucose-oxygen biofuel cell based on the nanostructured silica sol-gel/carbon nanotube composite electrodes generates ϳ120 W/cm 2 at 0.24 V when operated at room temperature.

Progress in the miniaturization of batteries has lagged well behind that of microelectronics. Although lithium‐ion (Li‐ion) battery technology has been vital in advancing portable consumer electronics, it is not clear whether future generations of microscale devices can be powered using traditional battery designs. In this paper, we report on the fabrication and properties of battery electrodes comprised of arrays of vertically aligned carbon rods. The electrodes exhibit good reversibility and represent the first carbon arrays to achieve areal capacities greater than 5 mAh cm−2 at relatively large current densities, although the capacity does fade with cycling. The 3D battery designs based on these architectures offer the promise of achieving high energy densities within small footprint areas.

Careful control of sol–gel chemistry allows for the encapsulation of water-reactive lithium polysulfides