NiFe-layered double hydroxide (NiFe–OH) is one of the most promising candidate materials for the oxygen evolution reaction (OER) in an alkaline electrolyte . However, it is difficult to be oxidized into Ni 3+ FeOOH active species with high valence Ni under mild conditions; thus, the activity under mild conditions is inferior. We report here that NiFe–OH is converted to amorphous NiFeO x H y (a3-NiFe-OH) with easily oxidized electron-deficient Ni 2+ after pre-oxidation in an alkaline solution boosts the OER performance under mild conditions. The amorphous structure of a3-NiFe-OH also enlarges the electrochemically active area to expose more active sites. It merely needs an overpotential of 350 mV at 10 mA cm −2 in 0.1 M KHCO 3 electrolyte. The corresponding Tafel slope is as low as 89 mV dec −1 . This work affords a strategy for developing (near) neutral OER catalysts.
Rong Wang,Chizhong Wang,Sihan Yin,Yue Peng,Jianjun Chen,Yanxi Deng,Junhua Li
Nickel iron (oxy)hydroxide (NiFeO x H y ) is among the most active electrocatalysts for oxygen evolution reaction (OER) in the alkaline media. Development of new design strategy for NiFeO x H y electrode with respect to intrinsic activity and number of active species is highly attractive. Here we report a hierarchical fabrication for NiFeO x H y electrode towards efficient oxygen evolution. Three-dimensional mesoporous NiO was initially prepared and reduced to a polycrystalline Ni metal framework. Despite the poor OER activity for Ni-based catalyst, the incorporation of surface Fe species induced a notably high current density for the oxygen evolution. The results indicated that the Fe species, located at outer surface region, played a key role as the OER active sites. It is also found that the surface of metallic Ni was reconstructed to (oxy)hydroxide phase with ease compared to NiO. As a result, a heterostructure composed of an OER-active NiFe (oxy)hydroxide shell and an electron-conductive Ni core was formed. In this fabricated NiFeO x H y /Ni catalyst, the promoted intrinsic activity, number of active sites and charge-transfer ability all taken into account contribute to an efficient OER process.
Yuan-Yuan Feng,Hua-Shuai Hu,Jin Liu,Zi-Heng Liu,Dan Zhang,Dong-Xing Tan
● S,Fe-NiFeO x H y /NF shows an ultra-low OER overpotential of 305 mV at 1000 mA cm −2 . ● The catalyst exhibits a promising stability for over 40 h without activity decay. ● The total preparation process of S,Fe-NiFeO x H y /NF electrocatalyst only takes 6 min. ● The high performance stems from electronic interactions among S, Fe and NiFeO x H y . Water electrolysis is considered an ideal route for producing high-purity hydrogen, yet its widespread application remains severely constrained by the anodic sluggish oxygen evolution reaction (OER). Herein, we present a high-performance S,Fe-NiFeO x H y /NF electrocatalyst for OER that markedly reduces the overpotential of OER to 196 mV at the benchmark current density of 10 mA cm −2 . Even at high current densities of 500 and 1000 mA cm −2 , the overpotentials are only 291 and 305 mV, respectively, outperforming most previously reported Ni/Fe-based catalysts. The catalyst also exhibits promising long-term stability, maintaining a high current density of 500 mA cm −2 for over 40 h without activity decay. Notably, the entire catalyst preparation takes just 6 min, and this cost-effective and facile synthetic strategy is key to enabling practical water electrolysis. Our findings open up a new avenue for developing non-noble metal catalysts with both high activity and durability for water electrolysis. Download: Download high-res image (267KB) Download: Download full-size image
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