Deciphering the amplification of dual catalytic active sites of Se-doped NiV LDH in water electrolysis: a hidden gem exposure of anion doping at the core-lattice LDH framework

Abstract

The advancement of highly efficient low-cost bi-functional electrocatalysts for water-splitting has significant importance in solving the energy crisis by producing an environment-friendly green energy. Herein, we have synthesized an efficient and durable class of NiV layered double hydroxide (LDH) on nickel foam (NF) as an electrocatalyst, which is improved synergistically in a structural way, and tuned electronically by Se inclusion. Surprisingly, after selenization, the LDH structure remains intact, confirming the successful doping of selenide ions in place of hydroxide in the core lattice structure of LDH. This is a very rare case of anion doping, which dramatically boosts the activity of OER, HER, and TWS. Experimental analysis proves that in 1 M KOH solution, Se-NiV LDH demands only 198 mV and 85 mV overpotentials for OER and HER, respectively, to attain the current density of 50 mA cm⁻². A 2-fold enhancement in the turnover frequency (TOF) value has also been observed in comparison to the bare electrocatalyst, which is superior to most of the previously reported Se-based LDHs. The total water splitting study of Se-NiV LDH shows a 1.54 V cell-voltage value to reach 10 mA cm⁻² current density with impressive 50 h stability. The observed downshift of the band-gap value from the Tauc-plot clearly explains both the improvement of the charge transfer kinetics and the electronic conductivity of the catalyst. Overall, our study provides a unique strategy to prepare the barely explored anion-doped bifunctional LDH and study its activity and stability towards total water splitting application.