Scientists Harness Crystals to Create Clean Energy Solution


Hematite, once regarded as a powerful tool by ancient shamans, and then disregarded as anything other than a shiny (and often magnetic) rock for many, many years, has once again been realized for its value in cultivating energy by modern scientists. For many years, scientists have struggled to find an efficient method to split water to mine electron-rich hydrogen for clean energy. It had always been found that Hematite could work, but its low performance stopped it from being a solution to clean energy… until now. By re-growing the minerals surface, a smoother version of hematite doubled the electrical yield, which then opened the door to harvesting energy using artificial photosynthesis. This was all published only in the last week in the journal Nature Communications. hemetiteformula

By simply smoothing the surface characteristics of hematite, this close cousin of rust can be improved to couple with silicon, which is derived from sand, to achieve complete water splitting for solar hydrogen generation,’ said Wang, whose research focuses on discovering new methods to generate clean energy. ‘This unassisted water splitting, which is very rare, does not require expensive or scarce resources.’

 

‘Upon running the tests, they immediately saw a dramatic improvement in voltage, as well as an increase of photovoltage from .24 volts to .80 volts, which was a dramatic increase in the amount of power generated than ever before seen!
The team described that with some more modifications, this hematite-silicon method of splitting water would be easily amenable to large scale utilization!Ematite508Not to mention, the re-growth technique might also be usable on other materials. Hematite may not be the only crystal that can do this, and if so, there are a lot of possibilities for this technology in the future.

‘This offers new hope that efficient and inexpensive solar fuel production by readily available natural resources is within reach,’ said Wang. ‘Getting there will contribute to a sustainable future powered by renewable energy.’

 

Better catalyst for solar-powered hydrogen production.


Hydrogen is a “green” fuel that burns cleanly and can generate electricity via fuel cells. One way to sustainably produce hydrogen is by splitting water molecules using the renewable power of sunlight, but scientists are still learning how to control and optimize this reaction with catalysts. At the National Synchrotron Light Source, a research group has determined key structural information about a potential catalyst, taking a step toward designing an ideal material for the job.

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Due to the mechanical and electrical complexity of the water-splitting reaction, there are many requirements in order for a catalyst to perform optimally. Scientists must understand not only a candidate’s local but also its structure over longer ranges – particularly the nanoscale, which tends to be a good indicator of a material’s electronic behavior and therefore its overall .

Scientists are increasingly focusing on a particular group of catalysts: cobalt-based thin films. These films are created via electrodeposition from aqueous solutions of cobalt mixed with an electrolyte. In this study, researchers from Columbia University, Harvard University, and Brookhaven Lab used x-rays to better understand the intermediate-range nanoscale structure of one of these films. They also investigated the structural differences between films grown using two electrolytes: phosphate, a negative phosphorous-oxygen ion, and borate, negative a boron-oxygen ion. The resulting films are denoted CoPi and CoBi, respectively.

X-ray scattering data from the CoPi and CoBi samples, taken at NSLS beamline X7B, indicate that both are nanocrystalline. This means that they consist of nanoscale grains, each ranging from about 1.5 to 3 nanometers (nm) in size with an ordered molecular structure. Aside from this, there are clear and important differences.

The CoBi films consist of 3-4 nm cobalate (cobalt–oxygen) clusters that stack neatly up to three layers deep. The CoPi films consist of significantly smaller clusters that do not stack in an ordered way.

These structural differences seem to tie into the films’ catalytic activity. Electrochemical data show that, as film thickness increased, the CoBi films were more active than CoPi and ultimately displayed a “significantly superior” performance. These findings suggest that the increase in CoBi film thickness also increases the effective surface area available for catalysis, while at the same time preserving the charge-transport properties of the films.

“Our results show a concrete difference between CoBi and CoPi, thus allowing the first insight into a tangible structure-function correlation,” said Harvard chemist and professor Daniel Nocera.