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

Abstract

Abstract: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.

Laser additive manufacturing of stainless steel micro fuel cells

“…This power density is nearly double compared to the silicon MFCs in Ref. [7] (127 mW cm À2 ) and an improvement compared to the aluminum MFCs in Ref. [18] (228 mW cm À2 ).…”

“…[7,18]: we have a square pillar flowfield and a basin for accommodating a commercial carbon cloth GDL. An exploded schematic view of the MFC construction is presented on Fig.…”

“…However, even with the high processing speeds achieved by methods such as laser ablation or CNC machining, the drawbacks of the serial subtractive approach come to the fore when large cavities must be produced. Many MFC designs require the presence of large volume cavities, such as fuel reservoirs [3,4,11], or basins to accommodate thick gas diffusion layers [7,18]. Speeding up CNC machining by using larger milling bits with CNC, or increasing laser ablation speed with larger beam waist and sustained power, is not usually feasible, as these actions would then make it impossible to create sufficiently small microchannels or inlet holes.…”

“…The electrical resistivity of 316L stainless steel is 74 mU cm, which compares favorably to the 10 mU cm of highly-doped silicon used in Refs. [7,20]. Because of the low electrical resistivity, the steel flowfield plates are good current collectors.…”

Enhanced performance of a silicon microfabricated direct methanol fuel cell with PtRu catalysts supported on few-walled carbon nanotubes

“…Therefore, a gradual coalescence of water droplets may occur in either catalyst layer, DL or flow channels which can increase mass transfer resistance and reduce the overall cell performance [46,47]. In another study [48] a layer of carbon cloth/felt on top of nanograss DL in a H2/O2 Si-MFC improved the performance of the cell. Therefore, including an additional layer of mesoporous DL in future studies may not only improve water removal management (at the cathode) and reactant distribution (at the anode) but also prevent migration/loss of catalyst particles from the support, all promoting durability of Si-MFCs.…”