Cheap, Robust Catalyst Splits Water Into Hydrogen And Oxygen

Splitting water into hydrogen and oxygen to produce clean energy can be simplified with a single catalyst developed by scientists at Rice University and the University of Houston. The electrolytic film produced at Rice and tested at Houston is a three-layer structure of nickel, graphene and a compound of iron, manganese and phosphorus. The foamy nickel gives the film a large surface, the conductive graphene protects the nickel from degrading and the metal phosphide carries out the reactionRice chemist Kenton Whitmire and Houston electrical and computer engineer Jiming Bao and their labs developed the film to overcome barriers that usually make a catalyst good for producing either oxygen or hydrogen, but not both simultaneously.

A catalyst developed by Rice University and the University of Houston splits water into hydrogen and oxygen without the need for expensive metals like platinum. This electron microscope image shows nickel foam coated with graphene and then the catalytic surface of iron, manganese and phosphorus

Regular metals sometimes oxidize during catalysis,” Whitmire said. “Normally, a hydrogen evolution reaction is done in acid and an oxygen evolution reaction is done in base. We have one material that is stable whether it’s in an acidic or basic solution.

The discovery builds upon the researchers’ creation of a simple oxygen-evolution catalyst revealed earlier this year. In that work, the team grew a catalyst directly on a semiconducting nanorod array that turned sunlight into energy for solar water splittingElectrocatalysis requires two catalysts, a cathode and an anode. When placed in water and charged, hydrogen will form at one electrode and oxygen at the other, and these gases are captured. But the process generally requires costly metals to operate as efficiently as the Rice team’s catalyst.

The standard for hydrogen evolution is platinum,” Whitmire explained. “We’re using Earth-abundant materials — iron, manganese and phosphorus — as opposed to noble metals that are much more expensive.

The robust material is the subject of a paper in Nano Energy.


Clean Renewable Source Of Hydrogen Fuel For Electric Car

Rice University scientists have created an efficient, simple-to-manufacture oxygen-evolution catalyst that pairs well with semiconductors for solar water splitting, the conversion of solar energy to chemical energy in the form of hydrogen and oxygen.

anode RiceA photo shows an array of titanium dioxide nanorods with an even coating of an iron, manganese and phosphorus catalyst. The combination developed by scientists at Rice University and the University of Houston is a highly efficient photoanode for artificial photosynthesis. Click on the image for a larger version

The lab of Kenton Whitmire, a Rice professor of chemistry, teamed up with researchers at the University of Houston and discovered that growing a layer of an active catalyst directly on the surface of a light-absorbing nanorod array produced an artificial photosynthesis material that could split water at the full theoretical potential of the light-absorbing semiconductor with sunlight. An oxygen-evolution  catalyst splits water into hydrogen and oxygen. Finding a clean renewable source of hydrogen fuel is the focus of extensive research, but the technology has not yet been commercialized.

The Rice team came up with a way to combine three of the most abundant metalsiron, manganese and phosphorus — into a precursor that can be deposited directly onto any substrate without damaging it. To demonstrate the material, the lab placed the precursor into its custom chemical vapor deposition (CVD) furnace and used it to coat an array of light-absorbing, semiconducting titanium dioxide nanorods. The combined material, called a photoanode, showed excellent stability while reaching a current density of 10 milliamps per square centimeter, the researchers reported.

The results appear in two new studies. The first, on the creation of the films, appears in Chemistry: A European Journal. The second, which details the creation of photoanodes, appears in ACS Nano.


Could Nanotechnology End Hunger?

Each year, farmers around the globe apply more than 100 million tons of fertilizer to crops, along with more than 800,000 tons of glyphosate, the most commonly used agricultural chemical and the active ingredient in Monsanto’s herbicide Roundup. It’s a quick-and-dirty approach: Plants take up less than half the phosphorus in fertilizer, leaving the rest to flow into waterways, seeding algae blooms that can release toxins and suffocate fish. An estimated 90 percent of the pesticides used on crops dissipates into the air or leaches into groundwater.

child starving

With the global population on pace to swell to more than nine billion by 2050 amid the disruptions of climate change, scientists are racing to boost food production while minimizing collateral damage to the environment. To tackle this huge problem, they’re thinking small — very small, as in nanoparticles a fraction of the diameter of a human hair. Three of the most promising developments deploy nanoparticles that boost the ability of plants to absorb nutrients in the soil, nanocapsules that release a steady supply of pesticides and nanosensors that measure and adjust moisture levels in the soil via automated irrigation systems.

It’s all part of a rise in precision agriculture, which seeks a targeted approach to the use of fertilizer, water and other resources. Recognizing the potential impact of nanotechnology, the U.S. Department of Agriculture’s National Institute of Food and Agriculture (NIFA) beefed up funding between 2011 and 2015, from $10 million to $13.5 million. India, China and Brazil are also joining the latest green revolution. Scientists led by Pratim Biswas and Ramesh Raliya at Washington University in St. Louis have harnessed fungi to synthesize nanofertilizer. When sprayed on mung bean leaves, the zinc oxide nanoparticles increase the activity of three enzymes in the plant that convert phosphorus into a more readily absorbable form. Compared to untreated plants, nanofertilized mung beans absorbed nearly 11 percent more phosphorus and showed 27 percent more growth with a 6 percent increase in yield.

Raliya and his colleagues are also developing nanoparticles that enhance plants’ absorption of sunlight and investigating how nanofertilizers fortify crops with nutrients. In a study earlier this year, they found that zinc oxide and titanium dioxide nanoparticles increased levels of the antioxidant lycopene in tomatoes by up to 113 percent. Next, they want to design nanoparticles that enhance the protein content in peanuts. Along with mung beans, peanuts are a major source of protein in many developing countries.

Others are exploring nanoparticles that protect plants against insects, fungi and weeds. The Connecticut Agricultural Experiment Station and other institutions recently began field trials that use several types of metal oxide nanoparticles on tomato, eggplant, corn, squash and sorghum plants in areas infected with fungi known to threaten crops. Researchers led by Leonardo Fernandes Fraceto, of the Institute of Science and Technology, São Paulo State University, Campus Sorocaba, are designing slow-release nanocapsules that contain two types of fungicides or herbicides to reduce the likelihood of targeted fungi and weeds developing resistance. Scientists at the University of Tehran are conducting similar research. Still others are working on nanocapsules that release plant growth hormones. Existing technology could increase average yields up to threefold in many parts of Africa.

How to Produce Hydrogen From Water At Low Cost

Cheaper clean-energy technologies could be made possible thanks to a new discovery. Research team members led by Raymond Schaak, a professor of chemistry at Penn State, have found that an important chemical reaction that generates hydrogen from water is effectively triggered — or catalyzed — by a nanoparticle made of nickel and phosphorus, two inexpensive elements that are abundant on Earth. The results of the research will be published in the Journal of the American Chemical Society. Schaak explained that the purpose of this nanoparticle is to help produce hydrogen from water — a process that is important for many energy-production technologies including fuel cells and solar cells. “Water is an ideal fuel, because it is cheap and abundant, but we need to be able to extract hydrogen from it,” Schaak said. Hydrogen has a high energy density and is a great energy carrier, Schaak explained, but it requires energy to produce. To make its production practical, scientists have been hunting for a way to trigger the required chemical reactions with an inexpensive catalyst. Platinum works, but it is expensive and relatively rare, so Schaak and his team have been searching for alternative materials.

hydrogen-electric carThere were some predictions that nickel phosphide might be a good candidate, and we already had been working with nickel phosphide nanoparticles for several years,” Schaak said. “It turns out that nanoparticles of nickel phosphide are indeed active for producing hydrogen and are comparable to the best known alternatives to platinum.”