美國賓夕法尼亞州立大學(xué)化學(xué)教授雷蒙德!薩克領(lǐng)導(dǎo)的研究團(tuán)隊近日發(fā)現(xiàn)，由儲量豐富且廉價的磷和鎳構(gòu)成的磷化鎳納米粒子可以成為制氫反應(yīng)的催化劑，為該反應(yīng)提速，最新研究將讓更廉價的清潔能源技術(shù)成為可能，相關(guān)論文將發(fā)表在《美國化學(xué)會志》上。

為了制造出磷化鎳納米粒子，研究團(tuán)隊使用經(jīng)濟(jì)上可行的金屬鹽進(jìn)行試驗。他們讓這些金屬鹽在溶劑中溶解，并朝其中添加了另外一些化學(xué)元素，然后加熱溶液，最終得到了一種準(zhǔn)球形的納米粒子——其并非完美的球形，因為擁有一些平的暴露的邊角。薩克解釋道：“納米粒子個頭小，但表面積很大，而且，暴露的邊緣上有大量的點可以為制氫反應(yīng)提速?！?/p>

接下來，加州理工學(xué)院化學(xué)系教授內(nèi)森!劉易斯領(lǐng)導(dǎo)的科研團(tuán)隊對這種納米粒子在反應(yīng)中的催化表現(xiàn)進(jìn)行了測試。研究人員首先將該納米粒子放在一塊鈦金屬薄片上，并將薄片沒入硫酸溶液中，隨后施加電壓并對生成的電流進(jìn)行了測試。結(jié)果表明，化學(xué)反應(yīng)不僅按照他們所希望的那樣發(fā)生了，效率也非常高。

薩克解釋道，磷化鎳納米粒子的主要作用是幫助人們從水中制造出氫氣，這一反應(yīng)對很多能源生產(chǎn)技術(shù)，包括燃料電池和太陽能電池來說都很重要。水是一種理想的燃料，因為其廉價且豐富，但我們需要將氫氣從中提取出來。氫氣的能量密度很高且是很好的載能體，但產(chǎn)生氫氣會耗費能量。

科學(xué)家們一直在尋找廉價的催化劑以便讓水制氫反應(yīng)更加實用且高效。薩克表示：“鉑可以很好地完成這件事，但鉑昂貴且稀少。我們一直在尋找替代鉑的材料。此前有科學(xué)家預(yù)測，磷化鎳會是好的‘替身’，我們的研究結(jié)果也表明，在制氫反應(yīng)中，磷化鎳納米粒子的表現(xiàn)的確可以和目前鉑的效果相媲美。”

薩克說：“納米粒子技術(shù)有望讓我們獲得更廉價且更環(huán)保的能源。接下來，我們打算進(jìn)一步改進(jìn)這些納米粒子的性能并厘清其工作原理。最新技術(shù)有望啟發(fā)我們發(fā)現(xiàn)其他也由儲量豐富的元素組成的催化劑，甚至其他更好的催化劑。”

Nanoparticle opens the door to clean-energy alternatives

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 University,have found that an important chemical reaction that generates hydrogen from water is effectively triggered—or catalyzed—by a nanoparticle composed 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 the nickel phosphide nanoparticle is to help produce hydrogen from water,which is 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.Schaak noted that this feat is accomplished very well by platinum but,because platinum is expensive and relatively rare,he and his team have been searching for alternative materials."There were some predictions that nickel phosphide might be a good candidate,and we had already 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."

To create the nickel phosphide nanoparticles,team members began with metal salts that are commercially available.They then dissolved these salts in solvents,added other chemical ingredients,and heated the solution to allow the nanoparticles to form.The researchers were able create a nanoparticle that was quasi-spherical—not a perfect sphere,but spherical with many flat,exposed edges."The small size of the nanoparticles creates a high surface area,and the exposed edges means that a large number of sites are available to catalyze the chemical reaction that produces hydrogen," Schaak explained.

The next step was forteam members at the California Institute of Technology to test the nanoparticles' performance in catalyzing the necessary chemical reactions.Led by Nathan S.Lewis,the George L.Argyros Professor of Chemistry at the California Institute of Technology,the researchers performed these tests by placing the nanoparticles onto a sheet of titanium foil and immersing that sheet in a solution of sulfuric acid.Next,the researchers applied a voltage and measured the current produced.They found that,not only were the chemical reactions happening as they had hoped,they also were happening with a high degree of efficacy.

"Nanoparticle technology has already started to open the door to cheaper and cleaner energy that is also efficient and useful," Schaak said."The goal now is to further improve the performance of these nanoparticles and to understand what makes them function the way they do.Also,our team members believe that our success with nickel phosphide can pave the way toward the discovery of other new catalysts that also are comprised of Earth-abundant materials.Insights from this discovery may lead to even better catalysts in the future."