本文中作者报道了一种新颖的方法，通过使用不锈钢布(SSC)作为沉积催化剂的载体，将氨合成与氢氧化进行配对，以克服四氢呋喃的传质限制。使用锂介导的方法获得的NH3的偏电流密度为8.8±1.4 mA cm-2，法拉第效率为35±6％。在两种非水溶剂中，H2氧化其电流密度可达25 mA cm-2，并且具有近乎统一的法拉第效率。

化学工程  电催化  能源

然而，这些方法不能克服对氨合成反应器本身的大规模生产的需求，因为氨合成反应器本身仍必须在高温和高压下运行。由N2和H2O产生氨的电化学过程（甚至利用多个反应器的过程）在标准条件下要求的热力学最小电势为1.17V。电势是一种强大的热力学驱动力，提供了有利于电化学过程的模块化和小规模运行的温和条件。 

对于阳极反应，通过在阳极上氧化H2来产生具有受控热力学活性的质子避免了上述问题。而且对于使用牺牲阳极的合成应用，氢氧化可用作可再生阳极反应，从而可以连续生产有用的化学物质。然而，氢在非水溶剂中的氧化速率受到氢化溶解度的限制，其相应的扩散限制氧化速率仍然过低，类似的扩散限制也适用于其他气体，如氮气。

淹没阻碍了标准碳纤维基GDEs与非水电解质的使用，以提高涉及稀溶气体的反应速率。尽管已经报道了克服这些问题的一些方法，但据我们所知，以前没有报道过的GDE能产生有效的气-液接触，从而大大增加了在非水溶剂中进行电合成所需的电流。

图3：基于钢布的GDE对HOR和NRR的效率

a. A comparison of the HOR Faradaic efficiencies of Pt/SSCs and Pt/C at different pressure gradients across the GDEs.

b. The effect of a pressure gradient across a Pt/SSC on the HOR Faradaic efficiency at 25 mA cm-2 applied current density is shown.

c. The production rate of ammonia as a function of applied current density on steel cloth cathodes at a pressure gradient of 1 kPa across the steel cloth is shown. Solution phase ammonia is found in the electrolyte whereas gas phase ammonia is found in the acid trap after the cell.

d. The effect of a pressure gradient across a steel cloth cathode on the Faradaic efficiency towards NH3 at 15 mA cm−2 applied current density.

The vertical error bars in a and b represent a combination of uncertainty in HOR quantification and standard deviation between experiments (n≥ 2), whereas in c and d they represent 1σ between multiple replicates of the same experiments (n≥ 2). Horizontal error bars in b and d represent the range of pressure gradient values required for gas flow through the SSCs. Raw data can be found in Supplementary Fig. 22 and Supplementary Tables 2–5. The dashed lines in b and d represent the onset of gas breakthrough in the SSC, which is the Laplace pressure. In all experiments, 7.2 C of charge were passed to measure either the HOR or NRR Faradaic efficiency

文章链接:

Non-aqueous gas diffusion electrodes for rapid ammonia synthesis from nitrogen and water-splitting-derived hydrogen

https://www.nature.com/articles/s41929-020-0455-8

导师简介:

Karthish Manthiram

B.S. Chemical Engineering, Stanford University, 2010

Ph.D. Chemical Engineering, UC Berkeley, 2015

Postdoctoral Research Associate, California Institute of Technology

Karthish Manthiram is an Assistant Professor in Chemical Engineering at MIT. He received his bachelor’s degree in Chemical Engineering from Stanford University and his Ph.D. in Chemical Engineering from UC Berkeley. As a graduate student in Professor Paul Alivisatos’ group, Karthish developed transition-metal oxide hosts for redox-tunable plasmons and nanoparticle electrocatalysts for reducing carbon dioxide. During his postdoctoral research in Professor Robert Grubbs’ lab at Caltech, Karthish developed new anion-exchange ionomers. The Manthiram Lab at MIT is focused on the molecular engineering of electrocatalysts for the synthesis of organic molecules, including pharmaceuticals, fuels, and commodity chemicals, using renewable feedstocks. Karthish’s research has been recognized with several awards, including the NSF CAREER Award, 3M Nontenured Faculty Award, Dan Cubicciotti Award of the Electrochemical Society, and Forbes 30 Under 30 in Science. Karthish’s teaching at MIT has been recognized with the C. Michael Mohr Outstanding Undergraduate Teaching Award in 2018 and the Outstanding Graduate Teaching Award in 2019.

信息来源：https://manthiramlab.com