Fully exposed edge/corner active sites in Fe substituted-Ni(OH)2 tube-in-tube arrays for efficient electrocatalytic oxygen evolution

Abstract The tremendous works focusing on long-range ordered hydroxides have ignored the investigation of the edge/corner sites in hydroxides, which is recently believed to be crucial for electrocatalytic activity enhancement of oxygen evolution reaction (OER). In this study, by anodic galvanostatic treatment in (NH4)2Fe(SO4)2 solution, the amorphous Ni(OH)2 (am-Ni(OH)2) is transformed into a short-range ordered Fe substituted-Ni(OH)2 (so-Fe-Ni(OH)2), which contains abundant electroactive edge/corner sites. To further enhance surface area, the special tube-in-tube arrays (TTAs) are fabricated for so-Fe-Ni(OH)2 to accelerate the reaction kinetics of OER. From DFT calculation, the low-coordinated defect sites with Fe-Ni-Fe units caused by the short-range ordered structure of so-Fe-Ni(OH)2 TTAs facilitate the formation of adsorbed oxygen, which is rate-determining step for efficient OER. The so-Fe-Ni(OH)2 TTAs show higher OER performance than long-range ordered Fe substituted-Ni(OH)2 (lo-Fe-Ni(OH)2). This study will provide a new strategy for electroactive edge/corner-site engineering of hydroxide-based electrocatalysts for efficient OER.