This is the first time that using only water and bacteria, researchers can continuously produce hydrogen-a potential source of clean energy. Scientists say that the challenge today is to scale up production to provide large amounts of hydrogen for a variety of uses, such as fueling cars and small generators.
Using a system of fresh water, salt water and bacteria, scientists produce hydrogen without any external energy.
Since only water vapor is generated after burning with oxygen, hydrogen may become the ultimate clean fuel. According to Bruce Logan, an environmental engineer at Pennsylvania State University, researchers have previously been able to produce hydrogen from fuel cells similar to batteries powered by microorganisms, but this process requires external energy to provide electricity, such as through renewable resources or burning fossil fuels. Logan also emphasized that with devices that contain permeable membranes that separate salt water and fresh water, scientists have been able to take advantage of the voltage difference that exists between them. However, these devices can only generate a voltage difference, but cannot create the current required to produce hydrogen. Only when an electric current passes through a liquid containing hydrogen ions can hydrogen atoms be produced, and these atoms combine to form hydrogen gas eventually.
Today, Logan and Younggy Kim, an environmental engineer at Pennsylvania State University, reported in this week ’s online edition of the Proceedings of the National Academy of Sciences that they have done something that other research teams have never done before – without any external energy Under the premise, the two devices were successfully combined to produce hydrogen. The prototype of the device consists of two parts: one part stores bacteria and their nutrients, and the other part stores salt water used to generate hydrogen gas-they are separated by five combined gas chambers to circulate salt water and fresh water. These combined gas chambers can produce a voltage of 0.5 to 0.6 volts-the researchers said that this is enough for the microbial fuel cell to produce hydrogen, and the bacteria in it feed on acetic acid compounds.
The researchers used 30 milliliters of sodium acetate solution to feed the bacteria. This device can produce 21 to 26 milliliters of hydrogen per day. There is no doubt that this is a very small volume-about four times the volume of disposable lighter fuel, but it is enough to prove that this concept of hydrogen production can work in the laboratory. Although the equipment for manufacturing hydrogen is expensive, this device does not require external energy, so no greenhouse gases will be produced during this process.
Chemist Leonard Tender of the US Naval Research Laboratory in Washington, DC pointed out that the research team's device was "very simple, and their experimental results were well explained and unambiguous." He emphasized that one of the challenges of expanding the scale of hydrogen production is to develop new materials needed for fuel cell membranes to prevent them from being quickly blocked by chemical by-products of bacterial activity-this will reduce the ion current required to maintain the voltage difference. Tender said that once this bottleneck is overcome, this technology will provide great possibilities for using the organic matter in wastewater to generate energy.
César Torres, a chemical engineer at the University of Arizona in Tempe, said that there is still a challenge to scale up production, which is "to keep the bacteria satisfied." Because if all the energy produced by bacterial metabolism is used to produce hydrogen, it will affect the growth and reproduction of microorganisms.
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