Sun Catalytix Ditches Artificial Leaf for Flow Batteries

March 9, 2013, By Sanjeev Ramachandran

MIT spin-off Sun Catalytix, which was supposed to be working an ‘artificial leaf’, has apparently dumped it for ‘flow batteries’.

A flow battery is a rechargeable fuel cell in which electrolyte containing one or more dissolved electroactive species flows through an electrochemical cell that converts chemical energy directly to electricity.

There are already dozens of flow batteries connected to the grid made by companies, employing vanadium and zinc bromide. Sun Catalytix however uses “designer molecules” made from abundant materials that are low-cost and environmentally friendly.


In flow batteries, additional electrolyte is stored externally, generally in tanks, and is usually pumped through the cell (or cells) of the reactor, although gravity feed systems are also used. Flow batteries can be rapidly ‘recharged’ by replacing the electrolyte liquid, while simultaneously recovering the spent material for re-energizing.

The move to focus on flow batteries is a dramatic turn for Sun Catalytix. The start-up was spun out of MIT in 2009 to commercialize a low-cost catalyst developed by Prof Daniel Nocera. He envisioned an “artificial leaf” that could cheaply strip the hydrogen from water and use the hydrogen in a fuel cell to make electricity.

The company raised venture capital from Polaris Venture Partners and from Indian conglomerate Tata. It also landed an ARPA-E grant for a material that can produce hydrogen from water directly from solar energy.

The company is currently in the process of filing for patents on flow battery technology. About half the 26 people at Sun Catalytix are chemical engineers and the other half are engineers, many of whom are from the fuel cell industry. Sun Catalytix faces a broad set of competitors vying to sell grid energy storage systems, which have very high demand. But for now they appear to be the front-runners.

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