CoFeNiMnZnB as a High-Entropy Metal Boride to Boost the Oxygen Evolution Reaction

Abstract

High-entropy materials offer numerous advantages as catalysts, including a flexible composition to tune the catalytic activity and selectivity and a large variety of adsorption/reaction sites for multistep or multiple reactions. Herein, we report on the synthesis, properties, and electrocatalytic performance of an amorphous high-entropy boride based on abundant transition metals, CoFeNiMnZnB. This metal boride provides excellent performance toward the oxygen evolution reaction (OER), including a low overpotential of 261 mV at 10 mA cm −2 , a reduced Tafel slope of 56.8 mV dec −1 , and very high stability. The outstanding OER performance of CoFeNiMnZnB is attributed to the synergistic interactions between the different metals, the leaching of Zn ions, the generation of oxygen vacancies, and the in situ formation of an amorphous oxyhydroxide at the CoFeNiMnZnB surface during the OER.

Excellent Bifunctional Oxygen Evolution and Reduction Electrocatalysts (5A1/5)Co2O4 and Their Tunability

“…This peak’s intensity is commonly utilized to measure the concentration of oxygen vacancies within the surface oxide lattice. The small peak observed at 533 eV is associated with water adsorption ( O H 2 normalO ) . This latter peak disappears after the OER activity, indicating a loss of adsorbed water.…”

Defective nickel sulfide hierarchical structures for efficient electrochemical conversion of plastic waste to value-added chemicals and hydrogen fuel

“…The high electrochemical dissolution of B has also been reported in previous studies on the OER. 46,47 The prominent co-etching of anions (S and B) contributes to more vacancies in the catalyst (Fig. S16 †) and facilitates the in situ structure reconstruction for the formation of the electroactive Co-doped NiOOH phase.…”

High entropy materials as emerging electrocatalysts for hydrogen production through low-temperature water electrolysis

“…In addition, for FeMnCoCrNi HEA catalysts [214], it was also reported that no Cr signal was detected by energy-dispersive spectroscopy or XPS after the OER stability test in 0.1 M KOH at 100 mA cm −2 for 60 h, indicating a remarkable compositional change upon OER. Besides, other transition metals such as Ni, Fe, Mo, Mn and Zn were also reported to dissolve to some extent from the HEM catalysts during OER [198,217,228]. Apart from dissolution, nonoxide HEMs (e.g.…”

“…Apart from dissolution, nonoxide HEMs (e.g. high entropy borides [217,219], or HESs [193]) would be converted into the corresponding oxides or hydroxides during OER, similar to monometallic and bimetallic compounds reported previously [188]. While currently the post-OER characterisation is mainly focused on the compositional changes of HEM catalysts including elements dissolution and oxidation, more comprehensive post-OER characterisation should be performed to elucidate microstructure and crystal structure changes as well; moreover, the stability number (i.e.…”