Promoting Nickel-Iron layered double hydroxide via In-situ sulfur doping for efficient bifunctional electrocatalysis and energy storage applications

Electrodes with multifunctional applications are essential to realize compact and cost-effective energy storage systems. Herein, we report the role of in-situ sulfur doping on nickel-iron-layered double hydroxide (NiFe-LDH) grown on nickel foam via the facile hydrothermal method. The effects of S-doping under different atomic percentages have been evaluated in terms of charge transport and morphological features. The in-situ mode of doping S helps to attain enhanced charge transport property without the detrimental S²⁻ substitution in OH sites of NiFe-LDH. The 5 at% doped NiFe-LDH (NFS05) demonstrates enhanced OER and HER properties with lower overpotentials of 304 mV and 99 mV, respectively. The NFS05 electrode demonstrated bifunctional activity with a low cell voltage of 1.60 V (@10 mA/cm²) in overall alkaline electrolysis. The empowered NFS05 has also been incorporated as an electrode in a supercapacitor configuration in which it demonstrated high specific and aerial capacitances of 212 F/g and 240.3 F/cm² at a current density of 0.25 A/g respectively. The improved electron density on the Ni and Fe sites via in-situ S doping together with enhanced surface-active sites are responsible for the NFS05’s superior electrode activity, which was decoded from X-ray photoelectron spectroscopy. This in-situ doping of S is found to be beneficial for realizing multifunctional electrodes for efficient electrochemical water splitting and energy storage systems with high stability.