Self-Supported Porous Ni-Fe-W Hydroxide Nanosheets on Carbon Fiber: A Highly Efficient Electrode for Oxygen Evolution...

Structural and compositional modulation of low-cost hydroxide is important for making efficient electrocatalysts of the oxygen evolution reaction (OER), and it is an ongoing challenge. Here, Ni-Fe-W hydroxide complex by incorporation of tungsten into nickel-iron layered double hydroxide was proposed and investigated. As-formed Ni-Fe-W hydroxide nanosheets are highly porous and self-supported on the carbon fiber substrates, which promote the exposure of the active metal sites for significantly enhanced OER activity. Moreover, the as-introduced tungsten is evidenced to be in a W⁶⁺ oxidation state which can facilitate charge transfer and electron capture and thereby decrease the critical conversion barrier of the absorbed OH^- to O radical in OER. A series of Ni-Fe-W hydroxides were prepared, with the best molar ratio of Ni-Fe-W sources being 6:2:1. The optimal Ni₆Fe₂W-LDH@carbon fiber electrode delivers a low overpotential of 264 mV at 10 mA cm^-2 and high stability (only 1.6% of the potential increase after 10 h) in alkaline electrolyte. Moreover, the structure of the constructed Ni-Fe-W hydroxide is evidenced to be stable and important for the electrocatalytically stable. The study is expected to open a new avenue in developing multiple hydroxides for low-cost and efficient electrocatalysts.