In response to society’s urgent drive to significantly decrease its reliance on fossil fuels in the future, there has been continuing efforts to utilize hydrogen (H₂) generated by water electrolysis as clean and sustainable substitute for the traditional fossil fuels. A significant challenge in water electrolysis revolves around creating affordable and efficient electrocatalysts to speed up the chemical reactions involved. Our new study introduces a bifunctional catalyst made from a high-entropy alloy (HEA), capable of efficiently catalyzing both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The findings reveal that a complex chemical composition of FeCoNiCuTi HEA can significantly modify its electronic structure, resulting in an impressive electrocatalytic performance. Specifically, FeCoNiCuTi HEA catalyst exhibits an overpotential of 64.9 mV at a current density of 10 mA cm⁻² for hydrogen evolution with a Tafel slope of 36.81 mV dec⁻¹ and double-layer capacitance (Cdl) of 34.1 mF cm⁻² . For oxygen evolution, HEA achieves an overpotential of 175 mV at 10 mA cm⁻² , a Tafel slope of 44.31 mV dec⁻¹ , exhibiting the performance superior to noble catalysts. Theoretical calculations support that the intricate chemical composition of high-entropy alloy plays vital role to enhance its electrocatalytic capabilities. This research represents a straightforward efficient method to create electrocatalysts for water electrolysis using non-noble metals by leveraging high-entropy effect.

The relevant research results are titled “Chemical dealloying derived nanoporous FeCoNiCuTi high-entropy bifunctional electrocatalysts for highly efficient overall water splitting under alkaline conditions”published in Chemical Engineering Journal ” is published in Chemical Engineering Journal!.

Fig. 1. (a) Schematic illustration of the water electrolysis. (b) XRD patterns of FeCoNiCuTi-x (x = 0, 2, 4, 10, 15, 20). (c) SEM images of FeCoNiCuTi-15. (d) SEM image from the selected area of (c). (e) HRTEM image, (f) SADE pattern and (g) TEM image with the corresponding elemental mapping results of FeCoNiCuTi-15.

Fig. 2. HER performance evaluation of FeCoNiCuTi-x (x = 0, 2, 5, 10, 15, 20) in 1.0 M KOH electrolyte: (a) Polarization curves. (b) Nyquist plots. (c) Tafel plots derived from polarization curves of (a). (d) Cdl values. (e) Stability test of FeCoNiCuTi-15 at 100 mA cm⁻² for 100 h.

Fig. 3. Ni-Top (Fe-Ni-Ti Ti): (a) Comparison of adsorption energy at different top adsorption sites. (b) Gibbs free energy (ΔGH* ) profiles on top adsorption sites in comparison with Pt (111). (c) Charge density difference diagram of Ni-Top site. (d) Structure comparison of the H adsorption before and after adsorption. Ni-Cu-Ti Fe: (e) Comparison of adsorption energy at different hollow sites. (f) Gibbs free energy (ΔGH* ) profiles on hollow adsorption sites in comparison with Pt (111). (g) Charge density difference of diagram of Ni-Cu-Ti Fe site. (h) Structure comparison of the H adsorption before and after adsorption.

Title:Chemical dealloying derived nanoporous FeCoNiCuTi high-entropy bifunctional electrocatalysts for highly efficient overall water splitting under alkaline conditions.

Author:Yezeng He ^a , Jiaojiao Qin ^a , Fangyu Hu ^a , Liang Mao ^a , Baolong Shen ^b,* ,Tejraj M. Aminabhavi ^c,d,* , Yasser Vasseghian ^e,f,* , Akbar Hojjati-

Najafabadi ^a,*.

DOI: https://doi. org/10.1016/j.cej.2024.152145.