The Fuel Cycle of the Future: Water to Fuel to Water

doi:10.21203/rs.3.rs-3596832/v1

Download PDF

Short Report

The Fuel Cycle of the Future: Water to Fuel to Water

https://doi.org/10.21203/rs.3.rs-3596832/v1

This work is licensed under a CC BY 4.0 License

Version 1

posted

You are reading this latest preprint version

Background: Fuel cells are a clean, renewable source of energy that may become the fuel of the future, next to solar, wind, geothermal energy.

Problem: There are many technological hurdles that must be fixed before hydrogen fuel cells replace pollutants like coal and oil. Hydrogen fuel cells are inefficient, and the process of creating hydrogen uses a lot of energy, so the problem tackled in this project is to optimize efficiency of hydrogen generation from electrolysis.

Hypothesis: We hypothesize that: 1. An increase in water temperature will increase efficiency 2. An increase in current through the cell will increase efficiency 3. The use of catalyst will increase efficiency.

Materials and Procedure: Using alligator clips a circuit was built, consisting of breadboard, power supply, voltmeter, and resistors. An electrolysis bath was created as described in detail in the paper. The data was collected in two sets: with and without catalyst (cobalt nitrate). For each set, the water temperature was increased to 75 degrees Celsius and was let to cool naturally to 22 degrees Celsius. Electrolysis was performed during cooling, using a current of approximately 3 mA.

Results: Every two degrees (C): the cell voltage was measured; the current was decreased to 2 mA and then to 1 mA and measurements were taken for those two currents as well, resulting in 3 cell voltage measurements for each temperature point; the current was then returned to 3 mA. The efficiency of reaction was calculated at start, baseline and after adding progressively more catalyst.

Conclusion: Hypothesis 1, the temperature dependency, was correct. Hypothesis 2 was the exact opposite of what we expected: the efficiency increased with a decrease in cell current. However, it is possible that in spite of having a better energy efficiency, the hydrogen output could have also been reduced. Hypothesis 3, the role of the catalyst, was also proven to have a substantial effect, especially at lower temperature and high current.

Electrochemistry

simple hydrogen fuel cells

catalyst

temperature dependence

Hydrogen fuel cells are very inefficient, and the process of creating hydrogen fuel uses a lot of energy. In this project, we are going to generate hydrogen through electrolysis and study the efficiency of a galvanostatic electrochemical cell as a function of temperature and current intensity, with and without catalyst (Cobalt Nitrate).

The main problems today are the expanding need for energy and the subsequent increasing pollution: cars burn fuel, which generates pollution; 70% of electricity is obtained from burning of fossil fuels (coal, oil, and natural gasses). The fossil fuels originate from organisms that died approximately 300 million years ago, they decomposed and through pressure and temperature changes turned into organic molecules made up of carbon, hydrogen and oxygen which made up coal, natural gases and oil. (1, 2) Scientists estimate that, by 2050, the United States will exhaust its reserve of fossil fuels, and as the process of creation of these fuels takes millions of years, is evident that the world has to come up with alternatives of renewable, clean energy.(1)

An alternative to internal combustion engines are electric vehicles; they do not pollute, but require batteries to store energy; this is inconvenient, since batteries require long charging times. (2, 3)

Fuel cells can be used as an alternative to batteries; they do not require long charging time and can operate on hydrogen. (4, 5) Hydrogen fuel cells utilize hydrogen and convert it into electricity which can be used to make more efficient electrical cars that don’t use batteries.

Hydrogen is the most abundant element in the Universe and represents the third most abundant element on Earth, where it is found in a multitude to chemical compounds (such as water), as well as in plants and animals. (2) Therefore, there is a clean infinite source of hydrogen that can be used in fuel cells. The history of hydrogen fuel cells dates back in 1671, when Robert Boyle discovered hydrogen through an experiment using iron and acid. (5) In the late 1700’s, people used hydrogen to float balloons because of its density being less than that of air. People then realized that hydrogen could be burned as a fuel, and Francois Isaac de Rivaz used hydrogen as fuel for the car with the first internal combustion engine. In the year 1839, Sir William Grove realized that electricity could be created by reversing electrolysis in water. Then in 1889, two researchers (Charles Langer and Ludwig Mond) invented the name: fuel cell. (5) Francis Bacon, however, was the first person to create a successful hydrogen fuel cell in 1932. (5) However, after the disaster of Hindenburg (1937), when a passenger aircraft caught on fire, people ceased using it. (5)

The best thing about hydrogen fuel cells is that they provide renewable energy, and they don’t pollute. However, there are many technological hurdles that must be fixed before hydrogen fuel cells replace pollutants like coal and oil. There are many problems with current day fuel cells, for instance: hydrogen is difficult to store, which would make it hard to put it in cars. (5) Hydrogen fuel cells are also very inefficient, and the process of creating hydrogen fuel uses a lot of energy. Hydrogen fuel cells are also very expensive, and there are very few hydrogen filling stations in the world. (4) Because of these reasons, it would be very hard to replace cheap nonrenewable pollutants like coal and oil with hydrogen fuel cells.

The hydrogen that fuel cells need can be extracted from water through electrolysis. There are many advantages to a galvanostatic electrochemical cell, because, unlike pollutants like coal and oil, it provides clean hydrogen. It also is renewable because the process of electrolysis creates water, which can be re-used. (4)

In this project, I create hydrogen for fuel cells through electrolysis and study ways to improve efficiency of electrolysis.

We hypothesize that the efficiency of electrolysis process (used to obtain hydrogen as a potential source for a fuel cell) can be improved by:

Plating the electrodes with cobalt nitrate, since plating will act as a catalyst in the reaction.
An increase in water temperature
An increase in current through the cell will increase efficiency

Background

One option for obtaining renewable energy is electrolysis/ water splitting, meaning that water molecules are broken apart into molecular hydrogen gas and oxygen gas. The hydrogen and oxygen can be stored separately, and later brought together as fuel in what is called a fuel cell. The combustion of hydrogen fuel produces energy and water as a byproduct, instead of carbon-based molecules, such as carbon dioxide and carbon monoxide, also known as greenhouse gases.(1) The water that is formed upon combustion of the hydrogen can be collected and reused in the electrolysis procedure to make more hydrogen fuel. This way, the cycle is self-sustainable. In order to make the electrolysis process more efficient, a catalyst needs to be used; the catalyst both increases the rate of reaction and reduces the energy necessary to produce hydrogen. Our experiment used a cobalt nitrate catalyst to determine if the electrolysis is more energy efficient.

Materials

− 30 Volt power supply and breadboard

- Alligator Clips (12)

− 9x 1k ohm resistor

- Digital Multimeter

− 250 ml glass beaker

Small Styrofoam piece
Nickel Metal Strips (2) (5 inches tall and ¾ inch wide)
Metal scoop for chemicals
Cobalt nitrate hexahydrate

− 0.1 M phosphate buffer solution, pH 7.0 (500 ml)

Measuring cup, 500 mL (6)
Digital thermometer
We then built a circuit (6, 7, 8) using alligator clips consisting of a breadboard, a power supply, a voltmeter, and resistors as shown in the next figure

The circuit (7, 8, 9) consists of:

A power supply (30 V, built in the breadboard),
9 x 1 Kohm resistors connected in series with the power supply
The two electrodes in the jar, connected in series with the power supply and resistors.
A voltmeter to measure the voltage across the electrodes

Preparation:

We verified that the voltmeter read 30v before the circuit was closed
We the inserted the two nickel electrodes partly into the Styrofoam
We then attached the electrodes to the circuit with alligator clips.
We filled the 500ml jar with 200ml of phosphate buffer
We placed the Styrofoam and electrodes on top of the jar so that electrodes were partly in phosphate buffer

Description of the experiment:

The data was collected in two sets: with and without catalyst. For each set, the water temperature was increased to 75 degrees Celsius and was let to cool naturally to 22 degrees Celsius. Electrolysis was performed during cooling, using a current of approximately 3 mA. Every two degrees (C):

the cell voltage was measured.
the current was decreased to 2 mA and then to 1 mA and measurements were taken for those two currents as well, resulting in 3 cell voltage measurements for each temperature point.
the current was then returned to 3 mA

We started with the electrolysis of water without catalyst to get a basic reading: we turned on power and measured the voltage across the electrodes. The voltage decreased over x minutes. We waited until the voltage stabilized.

Second, we started adding Cobalt nitrate in small quantities using the small metal scoop. We continued stirring and measuring the voltage across the electrodes. The voltage continued to decrease. We waited minutes until the voltage stabilized again.

We noticed a black substance depositing on the positive electrode as shown in the next picture. This substance is the plating.

We continued adding cobalt nitrate, stirring and measuring electrode voltage until we could not see any more change in voltage on the electrodes

Observations

The following table shows the results (steps: baseline, moments when we added nitrate; fill in duration)

Step	Time	Duration	Voltage
Start	4:29	1	2.14
1	4:30	1	2.06
2	4:31	1	2.04
3	4:32	1	2.03
4	4:33	1	2.01
5	4:34	1	2
6	4:35	1	1.99
7	4:36	1	1.98
8	4:37	1	1.98
9	4:38	2	1.98
Added one scoop of cobalt nitrate
10	4:40	6	1.98
11	4:46	13	1.85
Added one scoop of cobalt nitrate
12	4:59	1	1.81
13	5:00	10	1.78
14	5:10	3	1.8
Added one scoop of cobalt nitrate
15	5:13	8	1.78
16	5:21	0	1.78

This graph illustrates the variation of voltage with time and upon using the catalyst.

Data Analysis

We know from electrochemical literature (10) that in an ideal situation, the voltage required for water electrolysis is 1.23 volts. Any deviation from that value indicates that the reaction is less efficient than ideal.

We calculate the efficiency of the reaction as:

$$\varvec{e}\varvec{f}\varvec{f}\varvec{i}\varvec{c}\varvec{i}\varvec{e}\varvec{n}\varvec{c}\varvec{y}\left(\varvec{\%}\right)=\frac{\varvec{I}\varvec{d}\varvec{e}\varvec{a}\varvec{l} \varvec{v}\varvec{o}\varvec{l}\varvec{t}\varvec{a}\varvec{g}\varvec{e}}{\varvec{M}\varvec{e}\varvec{a}\varvec{s}\varvec{u}\varvec{r}\varvec{e}\varvec{d} \varvec{v}\varvec{o}\varvec{l}\varvec{t}\varvec{a}\varvec{g}\varvec{e}}\bullet 100\left(\varvec{\%}\right)$$

The following table shows the results of our experimentation, together with the time it required to achieve that point. The first column describes the event, the second describes the time it took the reaction to stabilize. The third column shows the voltage across the electrodes when the reaction was stabilized. The last column shown the efficiency of the reaction.

In conclusion, the hypothesis that the efficiency of the electrolysis process (used to obtain hydrogen as a potential source for a fuel cell) can be improved by plating the electrodes with cobalt nitrate, since plating will act as a catalyst in the reaction, was confirmed.

However, a few problems and questions arose, for example:

It is difficult to add small amounts of nitrate.
Stirring seems to affect the reaction; stirring too slowly or too violently seems to decrease the efficiency of the reaction.
The experiment was performed at room temperature, which is assumed to be constant; variations in temperature may modify the speed of reaction, independent of the catalyzer.

There are a few ways we could have improved this experiment:

By changing the current used in this reaction, the efficiency could be improved.
By choosing different catalysts, the efficiency could be improved further and the effect of different catalysts on the water splitting reaction can be compared.
Temperature could also influence the efficiency of the reaction and further testing at different temperatures, other than room temperature, may be pursued (for example temperatures around 5C versus 20C versus 30C) to determine the impact.

By using this galvanostatic electrochemical cell to generate hydrogen we are providing the fuel necessary for a fuel cell. The next step would be to capture the hydrogen generated and direct it into a fuel cell that would power the galvanostatic electrochemical cell, while the water resulted as a byproduct would be recycled back into the electrolysis process. This would create a power generating system that is self-sustainable.

I declare I have no conflict of interest

M.M Eboch. The 12 Biggest Breakthroughs in Energy Technology. Paw Prints, 2015.
Lew, Kristi. Goodbye, Gasoline: The Science of Fuel Cells. Compass Point Books, 2009.
Christensen, Victoria G. How Batteries Work. Lerner Publications, 2017.
Bayden, Maya. What Is Chemical Energy? Britannica Educational Publishing in Association with Rosen Educational Services, 2018.
Marquardt, Meg. Hydrogen Fuel Cells. Core Library, an Imprint of Abdo Publishing, 2017.
Science Buddies Staff. "Water to Fuel to Water: The Fuel Cycle of the Future" Science Buddies. Science Buddies, 6 Nov. 2017. Web. 14 Jan. 2018 <https://www.sciencebuddies.org/science-fair-projects/project-ideas/Chem_p099/chemistry/fuel-cell
Facts at Your Fingertips: Introducing Physics Electricity and Electronics. Brown Bear Books Limited, 2010.
Monroe, Ronald. What Are Electrical Circuits? Crabtree Publishing Co., 2012.
Roland, James. How Circuits Work. Lerner Publications, 2017.
Electrolysis of Water. Wikipedia, Wikimedia Foundation, 6 Jan. 2018, en.wikipedia.org/wiki/Electrolysis of water.

Download PDF

Version 1

posted

You are reading this latest preprint version

The Fuel Cycle of the Future: Water to Fuel to Water

Status:

Version 1

Abstract

Figures

Problem Statement

Background Research and Literature Review

Hypotheses

Background

Procedure, Experimental Design and Materials

Description of the experiment:

Observations

Data Analysis

Conclusions and Discussion

Implications for further research

Declarations

References

Status:

Version 1