Multi-high valence state metal doping in NiFe hydroxide toward superior oxygen evolution reaction activity

In this study, we demonstrate multi-high valence 3d transition metal (TM) doping to boost the oxygen evolution reaction (OER) activity and stability of NiFe hydroxide. Self-supported NiFe hydroxides with multiple high valence 3d TM (V4+, V5+, Ti3+, Ti4+, Co3+, and Cr3+) doping are fabricated using a facile Ni-corrosion method at room temperature without the use of any additional oxidizing agent. The high-valence metal dopants effectively tune the electronic structure of Ni. In situ Raman, ex situ electron energy-loss spectroscopy, and density functional theory calculations reveal that Cr is advantageous for the formation of oxyhydroxide with the longest Ni-O bond length, facilitating the decomposition of *OOH intermediate species for the generation of O-2. Additionally, Ti contributes to charge transfer. The optimized NiFe hydroxide with V, Ti, and Cr dopants (FNVTiCr) outperforms the benchmark RuO2 and reported Ni-based catalyst by exhibiting an overpotential of 240 mV at 100 mA cm(-2) and stability for 70 h. Notably, an alkaline electrolyzer with an FNVTiCr anode and Pt/C cathode is also demonstrated with an ultralow cell voltage of 1.49 V to generate a current density of 10 mA cm(-2), which is stable for 100 h, surpassing the benchmark industrial catalyst. This multi-high valence 3d TM doping approach provides a strategy for designing a low-cost, effective, and stable Ni-based catalyst.

Automated summary

In this study, multi-high valence 3d transition metal (TM) doping is demonstrated to enhance the oxygen evolution reaction (OER) activity and stability of NiFe hydroxide. Self-supported NiFe hydroxides with various high valence 3d TM dopants are prepared using a simple Ni-corrosion method. The high-valence metal dopants effectively modify the electronic structure of Ni and improve the catalytic performance of the NiFe hydroxide. The optimized NiFe hydroxide with V, Ti, and Cr dopants shows superior OER activity and stability compared to benchmark catalysts.