Making Microbial Fuel Cells
At the Logan Lab, we get a lot of questions about how to make an MFC and what materials we use. Well… it is not that simple. There are many types of configurations, and many different way to make electrodes and put them all together. To make it easier for people to choose what kind of MFC they want to make, and how to do that, we have put information on this page on materials, methods and configurations. In addition to the material on this page, see the photos of different types of MFCs and MxCs on this website, and visit the page on presentations which contains slides and videos on presentations on MFC. Be sure to see the MFC YouTube page and sign up for tweets (but we don’t send a lot of tweets).
HANDOUTS: Questions, and Getting Started
- Questions? – See this file on Answers to many different MFC questions (9-1-19). This has information on manufacturers of materials and whole MFCs. This file has great information for making your own MFC. We will update this as we answer questions from others.
- Handout with photos: Photographs of some earlier types of microbial fuel cells developed at Penn State – has pictures and short text explanation of various types of MFCs and MECs. For the best photos, go to the Photos page
Single-chamber, Air-cathode MFCs
- Cube-shaped MFC (28 mL): See this description of our cube MFC [Making a cube MFC] which holds 28 mL and has a cylindrical anode chamber. [MFC 4 cm cube] [2 cm cube]
- Larger, multiple brush MFC (150 mL): For continuous flow experiments we developed this multiple brush MFC that can have three or more brushes: 3 brushes (Ahn & Logan 2012); Lanas et al 2013)
- Single chamber bottle: MFC with side-arm air cathode: Watson & Logan (2010).
Two-chamber, Aqueous cathode MFCs
- 2 Bottle (H-Type) MFCs. There are several photos of these reactors on the photos page.
- Getting started: If you are doing a science project, here is a little guidance on making a simple two-chamber MFC using locally sourced materials (by Karl Shellenberger; 2005).
- Graphite fiber, brush anodes: Brush anodes work better than all others, as we first showed in a paper in 2007 (Logan et al., ES&T). A later analysis still shows that to be true [Analysis paper by Yang et al., Energy & Environmental Science, 2017). You can buy brush anodes from brush makers, for example we purchase them from Mill Rose. [Sources for bottle brushes] Bottle brush
- Heat treating brush anodes: The fibers on brushes should be cleaned to make it easier for bacteria to attach. Simply heat in a muffle furnace for 30 min at 450 deg C, chemical cleaning not needed. A regular oven set on the cleaning cycle works too. [Paper on heat treatment] [Paper on heat treatment by Feng et al, 2010, J. Power Sources]
- Ammonia-treated anodes: A procedure for the ammonia treatment of the anode. This increases power, but it is difficult and expensive, so we usually don’t do this anymore, and we just generally heat treat the anode.
- Graphite anodes: These are simple graphite plates. You can buy graphite from many vendors, for example see this page for Graphite materials available from McMaster-Carr. You many want to polish the electrodes to obtain consistent performance.
- Air cathode with Pt catalyst: You can buy carbon paper with Pt catalyst from the fuel cell earth, but if you use it without further modifications, it will leak water. Thus, you need to apply a diffusion layer (see below).
- Air cathode with 4 PTFE diffusion layers. You can download a step-by-step method for preparation of a cathode with Pt catalyst, binder, and four diffusion layers. This procedure requires a laboratory, but it is commonly used by many labs to make cathodes now. [original reference, Cheng et al. 2006, Electrochem. Comm]
- Air cathode with activated carbon and a single, thick PTFE layer: The first activated carbon cathode (Zhang et al. 2009, Electrochem. Commun.) was made by VITO in Belgium (using a proprietary method) and tested at Penn State. Several types of activated carbon cathodes have now been developed at Penn state.
- Air cathode by phase inversion, with an activated carbon catalyst and diffusion layer: A phase inversion cathode is easier to make than the 4 PTFE layer method, and the diffusion layer forms while it is made. There is a YouTube video on making this cathode. [Paper by Yang et al. 2015, Biores. Technol]
- Aqueous cathode, 2 Chamber MFC- Dissolved oxygen. You can use a cathode made of carbon paper with Pt (for example from fuel cell earth), but you have to aerate the water in the cathode chamber (for example with a fish pump). It will even work without the Pt catalyst, but the power will be very much lower than with a Pt catalyst.
- Aqueous cathode, 2 Chamber MFC- Ferricyanide catholyte: You can also use ferricyanide as the catholyte, but this requires use of an ion exchange membrane (to prevent the ferricyanide from crossing into the anolyte), and this chemical is not a sustainable solution. However, a plain carbon cloth, carbon paper or brush can be used to make the construction easy and inexpensive.
- Simple diffusion layer applied to cathode: A diffusion layer is on the air side of the cathode, and basically keeps water from leaking out. We have developed several procedures for this, with the original one based on adding PTFE. [Cheng et al. 2006, Electrochem. Comm]. A simpler alternative is to use a DMS diffusion layer (see Zhang et al 2010, IJHE) which will minimize water leakage if the cathode is not that big (doesn’t have a lot of water pressure). These work well compared to other options ( Zhang et al. 2017, ESWRT), and it is easy to apply, but it does not withstand water pressure very well.
- Cathode with GoreTex fabric: You can just use an old piece of GoreTex fabric if it is held pressed against the air side of the cathode (Luo et al. 2013, Biochem. Eng. J.)
- A defined medium. This is our standard MFC defined medium which is a rather complex laboratory medium as it has many added metals and vitamins. We have never seen a benefit of the vitamins, so they can probably be omitted for most MFC tests.
- Simple medium. You can make this using available media for a BOD test, as described in the Simple_Media_Instructions. We developed this very simple medium that we used for feeding our MFC_WebCam, a 2 L MFC that powered a fan.
- Inoculation? – Here is a procedure on how to inoculate an MFC with an acetate medium or wastewater, and this set of instructions has references to specific papers on the subject. Also, there is an an additional set of instructions for inocculation using a glucose medium. Acetate is generally the best substrate as it does not need to be broken down to generate electricity. Bacteria do not usually use glucose to produce electricity, so glucose must first be fermented to acetate to produce current.
- Comparing MFC startup methods: Different types of startup conditions were compared in a paper by Zhang et al. (2013, Biores. Technol.). Inoculation from another MFC is probably the best, but if that is not available, after starting your first MFC transfer solution into medium for the next MFC. The power will usually increase slightly when you transfer to a new MFC.
- Safety of the inoculum?– Some science fairs and competitions restrict microorganisms being studied to those that are known to be safe, so it may not allow you to use a wastewater inoculum or even lake sediment. You should consult the safety rules for your class or competition. Pure cultures can be purchased from culture collections such as ATCC.
- Non-ion selective separators: Separators can provide insulation between the electrodes so they don’t touch, but they also help to reduce oxygen crossover. A textile cloth works well, but it can degrade over time. (Zhang et al. Energy Environ. Scie, comparison of separators).
- Ion Exchange membranes: These are selective for anions and cations. Using them can result in large pH changes in the anode and cathode chambers, but anion exchange membranes (AEM) work better than cation exchange membranes (CEM) (Nafion is an expensive cation exchange membrane).(Kim et al. 2007, comparison of IX membranes).