Scrutinizing the redox activity of MOF-derived Fe–Se–C and P@Fe–Se–C species to improve overall water electrolysis and alkaline zinc–air batteries

Abstract

Versatile electrocatalysts made from Earth-rich elements are essential for the design of energy storage and conversion devices such as those involved in electrolytic water splitting and zinc–air batteries. In this research, MOF-derived rod-like Fe–Se–C and P@Fe–Se–C nanocatalysts were applied to modify various active species on catalytic structures. TEM, XRD, XPS, and XAS characterization of the MOF nanorod scaffold indicated a high abundance of catalytically active species, including the P@Fe–Se–C composite encased in Se on a carbon layer. High dual-functional activity of the OER with η₁₀ = 359 mV and the ORR with E_1/2 = 0.77 V, similar to those of commercial IrO₂ and Pt/C, was seen for Fe–Se–C. Additionally, the HER activity of the P@Fe–Se–C catalyst was η₁₀ = 211 mV. In addition, Zn–air batteries (ZABs) exhibited better charge–discharge cycling stability and an ideally stable open-circuit voltage of 1.58 V (P@Fe–Se–C). For overall water electrolysis, an optimal cell voltage of 1.43 V (P@Fe–Se–C) achieved a current density of 10 mA cm⁻². According to DFT, there was an important change in the electrocatalytic activity of P@Fe–Se–C and Fe–Se–C and the electronic structure, conductivity, and cycling stability of the catalyst over time. This study shows how creative material design can improve energy efficiency and provide multifunctionality.