Recent Developments in Mems-Based Micro Fuel Cells

Micro fuel cells ($\mu$-FC) represent promising power sources for portable applications. Today, one of the technological ways to make $\mu$-FC is to have recourse to standard microfabrication techniques used in the fabrication of micro electromechanical systems (MEMS). This paper shows an overview on the applications of MEMS techniques on miniature FC by presenting several solutions developed throughout the world. It also describes the latest developments of a new porous silicon-based miniature fuel cell. Using a silane grafted on an inorganic porous media as the proton-exchange membrane instead of a common ionomer such as Nafion, the fuel cell achieved a maximum power density of 58 mW cm-2 at room temperature with hydrogen as fuel.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Additive manufacturing: unlocking the evolution of energy materials

The global energy infrastructure is undergoing a drastic transformation towards renewable energy, posing huge challenges on the energy materials research, development and manufacturing. Additive manufacturing has shown its promise to change the way how future energy system can be designed and delivered. It offers capability in manufacturing complex 3D structures, with near-complete design freedom and high sustainability due to minimal use of materials and toxic chemicals. Recent literatures have reported that additive manufacturing could unlock the evolution of energy materials and chemistries with unprecedented performance in the way that could never be achieved by conventional manufacturing techniques. This comprehensive review will fill the gap in communicating on recent breakthroughs in additive manufacturing for energy material and device applications. It will underpin the discoveries on what 3D functional energy structures can be created without design constraints, which bespoke energy materials could be additively manufactured with customised solutions, and how the additively manufactured devices could be integrated into energy systems. This review will also highlight emerging and important applications in energy additive manufacturing, including fuel cells, batteries, hydrogen, solar cell as well as carbon capture and storage

Effects of Nano/Microstructures on Performance of Si-based Microfuel Cells

We investigated the effects of the contact surface structure of porous Si-based membrane electrode assemblies (MEAs) on the performance of microfuel cells, because the contact area of the triple-phase boundary among the MEA components plays an important role in the performance of polymer electrolyte fuel cells (PEFCs). An n-type silicon substrate was first wet-etched with KOH and subsequently anodically etched to fabricate a porous Si substrate. The cross section of the mechanically polished Si wafer showed pores with high aspect ratios. Electrolyte solutions were filled into the pores to prepare a porous Si membrane (PSM), and the MEA was fabricated by hot-pressing the PSM between two conventional catalyst-coated carbon-paper electrodes. The porous Si-based MEA worked well and showed a power density higher than that of the Nafion®-212-based membrane. Further, we examined the effects of the nano/microstructures at the triple-phase boundary and found that the more densely arranged nano/microstructures reduced the magnitudes of the activation overvoltage and ohmic overvoltage, thereby improving the cell performance.International Symposium on Innovative Materials for Processes in Energy Systems 2013 (IMPRES2013), September 4-6, 2013 in Fukuoka, Japan

Development of enzymatic biofuel cell based on carbon nanotube electrodes on porous silicon

The work presented in this thesis has focused on designing and characterizing biofuel cell electrodes using porous silicon (p-Si) as the substrate or current collecting platform on which carbon nanotubes (CNTs), both single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MiWNTs), were synthesized directly, followed by enzyme catalyst immobilization on the CNTs. Laccase and glucose oxidase (GOx) were used as enzymatic biocatalysts, which were immobilized on the CNT walls and tips using an electrochemical technique. Cyclic voltammetry showed well-defined redox peaks which indicated that the enzyme (GOx and laccase) were successfully immobilized on the CNTs. The amperometric responses of the laccase electrode upon additions of bubbled air and potentiometric responses of GOx electrode to additions of glucose demonstrated that the immobilized enzymes retained their bioelectrocatalytic activity after electrochemical deposition. Working biofuel cells with p-Si/SWNTs and p-Si/MWNTs based electrodes with immobilized enzymes were studied at room temperature in a 0. iM phosphate buffer solution of pH 7.0, containing 4 mM glucose. The peak power output of the biofuel cell with p-SiISWNTs based electrodes was 3.32 μW at 357 mV vs. SCE (Saturated Calomel Electrode). It provided much better performance than the biofuel cell with p-Si/MWNTs electrodes, which yielded a peak power of 1.23 nW at 5.6 mV. The combination of p-Si/CNTs with redox enzymes provided a convenient prototype for a direct electron transfer, membrane-less biofuel cell

Single Compartment Micro Direct Glucose Fuel Cell

Micro fuel cells have received considerable attention over the past decade due to their high efficiency, large energy density, rapid refuelling capability and their inherent non-polluting aspect. An air breathing abiotically catalyzed single compartment micro direct glucose fuel cell (SC-µDGFC) has been developed using microfabrication technologies. The single compartment of the fuel cell was shared by the anode and cathode that had an interdigitating comb electrodes configuration. The SC-µDGFC compartment was formed of polydimethylsiloxane (PDMS) which exhibits high permeability to oxygen and served as the membrane through which oxygen from ambient environment was able to permeate to the cathode. To minimize the losses associated with fuel crossover, two features were incorporated in the fuel cell: (i) silver was used as the catalyst to selectively reduce oxygen in the presence of glucose and (ii) cathodes were made 25-45µm higher than the anode to reduce access of oxygen to the anode with nickel or platinum catalyst. For 1M glucose/2M KOH solution, an initial OCV of 120-160mV was recorded, which gradually decreased with time and stabilized at 60-75mV. For a fuel cell tested without PDMS membrane, maximum OCV of 135mV and power density of 0.38µW/cm2 was obtained

Effects of Nano/Microstructures on Performance of Si-based Microfuel Cells

We investigated the effects of the contact surface structure of porous Si-based membrane electrode assemblies (MEAs) on the performance of microfuel cells, because the contact area of the triple-phase boundary among the MEA components plays an important role in the performance of polymer electrolyte fuel cells (PEFCs). An n-type silicon substrate was first wet-etched with KOH and subsequently anodically etched to fabricate a porous Si substrate. The cross section of the mechanically polished Si wafer showed pores with high aspect ratios. Electrolyte solutions were filled into the pores to prepare a porous Si membrane (PSM), and the MEA was fabricated by hot-pressing the PSM between two conventional catalyst-coated carbon-paper electrodes. The porous Si-based MEA worked well and showed a power density higher than that of the Nafion®-212-based membrane. Further, we examined the effects of the nano/microstructures at the triple-phase boundary and found that the more densely arranged nano/microstructures reduced the magnitudes of the activation overvoltage and ohmic overvoltage, thereby improving the cell performance

Integrated Micro Fuel Processor And Flow Delivery Infrastructure

Apparatus for transporting a fluid, atomizers, reactors, integrated fuel processing apparatus, combinations thereof, methods of atomizing reactants, methods of moving fluids, methods of reverse-flow in a reactor, and combinations thereof, are provided. One exemplary apparatus for transporting a fluid, among others, includes: a channel for receiving a fluid; a sensor for determining an internal condition of the fluid in the channel; and a channel actuator in communication with the sensor for changing a cross-sectional area of the channel based on the internal condition, wherein the change in cross-sectional area controls a parameter selected from a pressure and a fluid flow.Georgia Tech Research Corporatio