Petri Kanninen

Transparent and flexible high-performance supercapacitors based on single-walled carbon nanotube films

Transparent and flexible energy storage devices have garnered great interest due to their suitability for display, sensor and photovoltaic applications. In this paper, we report the application of aerosol synthesized and dry deposited single-walled carbon nanotube (SWCNT) thin films as electrodes for an electrochemical double-layer capacitor (EDLC). SWCNT films exhibit extremely large specific capacitance (178 F g(-1) or 552 μF cm(-2)), high optical transparency (92%) and stability for 10 000 charge/discharge cycles. A transparent and flexible EDLC prototype is constructed with a polyethylene casing and a gel electrolyte.

Integration of carbon felt gas diffusion layers in silicon micro fuel cells

We have integrated carbon felt, a traditional fuel cell gas diffusion layer, with silicon micro fuel cells. To this end we used two silicon microfabrication procedures using reactive ion etching: formation of black silicon and sinking of flowfield. The former decreases electrical contact resistance to the diffusion layer, the latter serves to contain the reactant gases. The micro fuel cells, where the flowfield was covered by black silicon nano-needles, showed better performance (127 mW cm−2) compared to the same cells without black silicon (114 mW cm−2). The black silicon fuel cells were also more stable during an overnight chronoamperometric measurement.

Bulk-Aluminum Microfabrication for Micro Fuel Cells

We present a simple method for microfabricating microfluidic devices by wet etching of bulk aluminum wafers. Aluminum wafers are identical to silicon wafers in terms of dimensions and can easily be processed in standard clean room processes like lithography, etching, and thin film deposition. Aluminum thin film wet etching in phosphoric acid-based etchants is well established. In this paper, it is extended to much greater depths than before. 80 μm deep structures have been fabricated. A hydrogen-fueled micro fuel cell has been microfabricated from bulk aluminum. These fuel cells achieved very high current densities of 1.1 A cm-2 and power density up to 228 mW cm-2. Considering the simplicity of bulk aluminum micromachining, these results are very encouraging.

Stretchable and transparent supercapacitors based on aerosol synthesized single-walled carbon nanotube films

Stretchable all-solid supercapacitors based on aerosol synthesized single-walled carbon nanotubes (SWCNTs) have been successfully fabricated and tested. High quality SWCNT films with excellent optoelectrical and mechanical properties were used as the current collectors and active electrodes of the stretchable supercapacitors. A transmittance of up to 75% was achieved for supercapacitors made from the assembly of two PDMS/SWCNT electrodes and a gel electrolyte in between. The transparent supercapacitor has a specific capacitance of 17.5 F g−1 and can be stretched up to 120% with practically no variation in the electrochemical performance after 1000 stretching cycles and 1000 charging–discharging cycles.

Test of different anode electrocatalysts for direct glucose anion exchange membrane fuel cell

Direct glucose anion exchange membrane fuel cell (AEMFC) with near-neutral-state electrolyte of 0.1 M [PO4] (tot) was studied with five different anode electrocatalysts (Pt, PtRu, PtNi, Au, PdAu) a ...

Towards an efficient direct glucose anion exchange membrane fuel cell system with several electro-oxidation units

This work covers the direct glucose anion exchange membrane fuel cell (AEMFC) with near-neutralstate electrolyte of 0.1 M [PO4] (tot) having two high-performing anode electrocatalysts (Pt and PtNi) ...

Symmetric silicon micro fuel cell with porous electrodes

We have developed a silicon microfabricted PEM fuel cell which uses hydrogen as fuel. The device employs flow channels with dual structure: isotropic plasma etching has been used for defining the large channels and gas conduits, and anisotropic plasma etching under passivating conditions (high concentration of oxygen in SF6) has been used to create silicon nanograss (black silicon) to increase surface area and triple junction points. The design presented here achieves the following goals: simple and cheap to fabricate, high power density (45mW/cm2), longevity and integrability.

Simple Stacking Methods for Silicon Micro Fuel Cells

Abstract: We present two simple methods, with parallel and serial gas flows, for the stacking of microfabricated silicon fuel cells with integrated current collectors, flow fields and gas diffusion layers. The gas diffusion layer is implemented using black silicon. In the two stacking methods proposed in this work, the fluidic apertures and gas flow topology are rotationally symmetric and enable us to stack fuel cells without an increase in the number of electrical or fluidic ports or interconnects. Thanks to this simplicity and the structural compactness of each cell, the obtained stacks are very thin (~1.6 mm for a two-cell stack). We have fabricated two-cell stacks with two different gas flow topologies and obtained an open-circuit voltage (OCV) of 1.6 V and a power density of 63 mW·cm −2 , proving the viability of the design. Keywords: silicon; micro fuel cell; stacking; deep reactive ion etching; polymer electrolyte membrane; black silicon 1. Introduction Fuel cells have been traditionally used for stationary power generation or in electrical vehicles, but miniaturized micro fuel cells (micro FC) have been, more recently, researched as a viable alternative to rechargeable batteries for applications, such as mobile phones, MP3 players, camcorders,