Green Chemistry in Energy Storage

By Mark Miltenburg, Member-at-Large for the GCI

Batteries are not usually thought of as very “green” technologies. They typically employ toxic heavy metals and scarce elements, and they are not often recycled very effectively [1, 2]. However, their increasing usage in applications such as cell phones and electric vehicles has led to these factors being overlooked compared to improvements in cost and performance.

I recently came across a paper in the journal Nature on a new redox-flow battery [3]. Redox-flow batteries (RFBs) are stationary energy storage devices primarily used as on-site redundant power sources, and could potentially be used to store energy from intermittent renewable sources like solar or wind.

Redox_Flow_Battery_English

Schematic of a redox flow battery, consisting of a redox flow cell and two tanks used to store electrolyte solutions. The colour change demonstrates the reduction or oxidation of the solution. [4]

In this paper, the authors improve upon existing RFBs in three key areas: cost, safety, and scalability. This directly addresses at least 3 of the 12 principles of green chemistry as explained below [5].

Traditional RFBs use expensive and non-scalable materials like lithium or vanadium. This paper replaces these materials by employing inexpensive and environmentally friendly polymers for use as active materials. These polymers were able to approach conventional vanadium-based RFBs in performance, while being shown to be significantly less toxic than vanadium compounds. This greatly improves the cost and scalability of RFBs for future applications. This hits principle number 4: Chemical products should be designed to preserve efficacy of function while reducing toxicity.

The authors also were able to replace the electrolyte, usually based on sulfuric acid, with a non-corrosive, non-toxic sodium chloride solution. This is very important for RFBs due to the sheer size of RFB installations, which contain several tonnes of electrolyte. This checks off principle number 12: Substances and the form of a substance used in a chemical process should be chosen to minimize potential for chemical accidents, including releases, explosions and fires.

In addition, the authors were able to replace one of the most expensive elements of traditional RFBs. The use of Nafion, a perfluorinated polymer used to make conducting membranes, is common due to the chemical stability required by sulfuric acid electrolytes. However, Nafion accounts for 40% of the cost of a reaction cell. The authors replaced Nafion membranes in their battery with inexpensive cellulose-based dialysis membranes, which were compatible with the milder sodium chloride electrolyte. On top of the cost benefit, this touches on principle number 10: Chemical products should be designed so that at the end of their function they do not persist in the environment and break down into innocuous degradation products. Nafion is very stable and does not easily break down, while cellulose naturally degrades into polysaccharides or glucose.

I really enjoyed this paper, as it demonstrated to me that you are able to make significant improvements to existing technologies by making them greener. In the case of RFBs, a spin-off company is licensing this technology already, making use of the cost and safety benefits brought about by green chemistry. It is one more example that sustainable thinking does not necessarily have to hurt a company’s bottom line.

References:

[1] Gupta, S. Nature 2015, 526 (7575), S90–S91.

[2] Gies, E. Nature 2015, 526 (7575), S100–S101.

[3] Janoschka, T. et al. Nature 2015, 527 (7576), 78–81.

[4] Image created by Nick B, distributed under a CC BY-SA 3.0 license. https://commons.wikimedia.org/wiki/File:Redox_Flow_Battery_English.png.

[5] Anastas, P. T.; Warner, J. C. Green Chemistry: Theory and Practice, Oxford University Press: New York, 1998, p.30.

Why I Do Green Chemistry

By Mark Miltenburg, Member-at-Large for the GCI

Mark GCI Blog

This is my green chemistry story. What’s yours? Tell us in the comments!

One of the greatest challenges that scientists face is communicating our work effectively to people outside of our field. This partly stems from researchers getting lumped together as part of a faceless group of “chemists” or “scientists,” rather than being perceived as individual members. Nobody enjoys a group dictating to him or her what to think or do, so this dehumanized entity causes difficulty in getting people to listen to what you have to say. I have even noticed this problem as a member of the GCI trying to reach other chemists; our message gets understood very differently from what we intend because people hear the word “green” and immediately assume that as a member of the GCI I am judging them and their work, which is certainly not the case.

In an effort to combat this, I thought I would use my turn writing the GCI blog to try and humanize our group a bit by sharing my own reasons for joining the GCI and what I hope other chemists can take away from our work, and inviting others to share their own stories about their interests in green chemistry.

I did a co-operative program for my undergraduate degree, and as part of my work placements, I got to interact with scientists and engineers at major companies such as Honda Canada Inc., Diageo plc, and Rockwell Automation. I saw firsthand the industrial chemical systems that are used, and the scales at which they operate. Viewed on this scale, green chemistry just makes sense, as these places spend huge sums of money disposing of enormous amounts of waste and ensuring that they are operating under safe working conditions. As a result of this scale, these companies are constantly looking for greener solutions, as they make sense from both economical and publicity standpoints. I think Dr. Cameron Cowden, Executive Director of Process Research at Merck & Co., Inc., said it very well at our GCI Workshop when he remarked that green chemistry “is just smart chemistry.”

Simple Techniques to Make Everyday Lab Work Greener

Here are 10 simple tips to make everyday lab work greener. Feel free to print it out and post it in your own lab!

As a graduate student, I know that for most of us it is impossible to completely overhaul our research in order to make it completely green, and I don’t think that’s the aim of the GCI; we are all graduate students who want to graduate someday. We only hope to educate chemists so that they are aware of solvents,waste, etc. when they go about their research, and trust that when these things are actively taken into consideration, chemists will naturally make an effort to make their research greener. I also know that there are relatively simple ways to make research greener, which won’t impact results, and aren’t currently used because many people are not aware of them. For a great resource on some of these simple techniques, check out this poster prepared by the GCI (and hang it in your lab to share it with others!).

What made you interested in green chemistry? Add your stories in the comments.