Researchers at Washington State University, with colleagues at Argonne National Laboratory and Pacific Northwest National Laboratory, have combined inexpensive nickel and iron in a very simple, five-minute process to create large amounts of a high-quality catalyst required for water splitting.
By in situ reduction of the metal precursors, the researchers synthesized compositionally controlled three-dimensional NixFey nanofoams (NFs) with high surface area and uniformly distributed bimetallic networks. In a paper in the journal Nano Energy, the team reported that the resultant ultrafine and highly disordered amorphous Ni2Fe1 NFs exhibited “extraordinary” electrocatalytic performance toward OER (oxygen evolution reaction) and overall water splitting in alkaline media.
|SEM image of NiFe nanofoams. WSU researchers can create large amounts of inexpensive nanofoam catalysts that can facilitate the generation of hydrogen on a large scale by water splitting. Source: WSU. Click to enlarge.|
Electrolysis of water is considered as an easy and clean method to obtain hydrogen. Oxygen evolution reaction (OER), however, as one of the two important reactions (hydrogen evolution reaction as the other part) involved in electrolysis, is the bottleneck for practical water splitting applications. The sluggish kinetics and large overpotential of OER make it imperative to search for high-performance electrocatalysts. In the last few decades, RuO2 and IrO2 are regarded as the state-of-the-art catalysts for OER thanks to their good catalytic activities and stabilities. However, the scarce resource and prohibitive cost of these precious metals hurdle their further commercial applications. Accordingly, increasing attentions have been paid on exploring highly active, cost-effective and durable alternatives, such as first-row transition metal alloys, oxides, hydroxides and phosphides.
Among them, Ni-based catalysts have been demonstrated to be competent candidates with low overpotential and superior stability under alkaline conditions. In particular, bimetallic catalysts composed of Ni and additional secondary transition metals, especially NiFe electrocatalysts, are reported to show much better catalytic performance for OER compared to the single component counterparts.
… One of the most efficient strategies to improve the OER performance of transition metal catalysts is to expose more active sites by increasing the surface area of the catalyst. … Herein, we proposed a rapid and facile procedure to synthesize 3D porous NixFey nanofoams (NFs) with ultrafine and highly disordered structure.—Fu et al.
At a potential as low as 1.42V (vs. RHE), the Ni2Fe1 NFs can deliver a current density of 10mA/cm2 and show negligible activity loss after a 12h stability test. Even at a large current flux of 100mA/cm2, an ultralow overpotential of 0.27V is achieved—about 0.18V more negative than benchmark RuO2.
The researchers suggested that the evolution of the oxidation state and the disordered structure of Ni2Fe1 might be a key to the high catalytic performance for OER.
The researchers are now seeking additional support to scale up their work for large-scale testing. The collaborative work was funded by a WSU startup grant and by the US Department of Energy.
Shaofang Fu, Junhua Song, Chengzhou Zhu, Gui-Liang Xu, Khalil Amine, Chengjun Sun, Xiaolin Li, Mark H. Engelhard, Dan Du, Yuehe Lin (2018) “Ultrafine and highly disordered Ni2Fe1 nanofoams enabled highly efficient oxygen evolution reaction in alkaline electrolyte,” Nano Energy, Volume 44, Pages 319-326 doi: 10.1016/j.nanoen.2017.12.010.