Bau Jeremy A, Luber Erik J, Buriak Jillian M
National Institute for Nanotechnology (NINT), National Research Council, 11421 Saskatchewan Drive, Edmonton, Alberta T6G 2M9, Canada.
Department of Chemistry, University of Alberta , Edmonton, Alberta T6G 2G2, Canada.
ACS Appl Mater Interfaces. 2015 Sep 9;7(35):19755-63. doi: 10.1021/acsami.5b05594. Epub 2015 Aug 27.
Mixed nickel-iron oxides are of great interest as electrocatalysts for the oxygen evolution reaction (OER), the kinetically challenging half-reaction required for the generation of hydrogen gas from water via electrolysis. Previously, we had reported the synthesis of single crystal, soluble nickel-iron oxide nanoparticles over a wide range of nickel:iron compositions, with a metastable cubic rock salt phase ([Ni,Fe]O) that can be isolated despite the low solubility of iron in cubic nickel oxide at ambient temperatures. Here, activity for OER was examined, catalyzed by these [Ni,Fe]O nanoparticles integrated with indium tin oxide (ITO) electrodes. Because the as-prepared [Ni,Fe]O nanoparticles are oleate-capped, the surface ligands needed to be removed to induce adherence to the ITO substrate, and to enable charge transfer and contact with water to enable OER catalysis. Two different approaches were taken to reduce or eliminate the coverage of oleate ligands in these films: UV irradiation (254 nm) and air plasma. UV irradiation proved to lead to better results in terms of stable and OER-active films at pH 13. Kinetic analysis revealed that the Tafel slopes of these nanoparticle [Ni,Fe]O OER electrodes were limited by the electrochemical surface area and were found to be within the range of 30 to 50 mV/decade. Across the four compositions of Ni:Fe studied, from 24:76 to 88:12, the observed overpotential at 10 mA/cm2 for the OER in basic conditions decreased from 0.47 to 0.30 V as the proportion of nickel increased from 24% to 88%.
混合镍铁氧化物作为析氧反应（OER）的电催化剂备受关注，OER是通过电解从水中产生氢气所需的动力学上具有挑战性的半反应。此前，我们报道了在广泛的镍铁组成范围内合成单晶、可溶的镍铁氧化物纳米颗粒，其具有亚稳立方岩盐相（[Ni,Fe]O），尽管在环境温度下铁在立方氧化镍中的溶解度较低，但该相仍可分离出来。在此，研究了这些与氧化铟锡（ITO）电极集成的[Ni,Fe]O纳米颗粒催化的OER活性。由于制备的[Ni,Fe]O纳米颗粒被油酸盐包覆，需要去除表面配体以诱导其附着在ITO基底上，并实现电荷转移以及与水接触以实现OER催化。采用了两种不同的方法来减少或消除这些薄膜中油酸盐配体的覆盖：紫外线照射（254 nm）和空气等离子体。在pH值为13时形成稳定且具有OER活性的薄膜方面，紫外线照射被证明能产生更好的效果。动力学分析表明，这些纳米颗粒[Ni,Fe]O OER电极的塔菲尔斜率受电化学表面积限制，且发现其在30至50 mV/十倍电流密度的范围内。在所研究的镍铁的四种组成中，从24:76到88:12，随着镍的比例从24%增加到88%，在碱性条件下OER在10 mA/cm²时观察到的过电位从0.47 V降至0.30 V。
