Atomically Dispersed Bimetallic FeNi Catalysts as Highly Efficient Bifunctional Catalysts for Reversible Oxygen Evolution and Oxygen Reduction Reactions

Abstract

Bimetallic atomically dispersed FeNi catalysts anchored on N‐doped carbon nanotube with catalyst loading of 2–7 wt % with different Fe : Ni ratio have been developed as highly active and stable bifunctional catalyst for reversible oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) for metal air batteries via a modified one‐pot synthesis method. Compared with atomically dispersed single Fe and Ni catalysts, the bimetallic FeNi catalysts exhibit outstanding performance for reversible OER and ORR, achieving a low potential gap (ΔE) of 0.81 V to deliver an OER current density of 10 mA cm−2 and an ORR current density of 3 mA cm−2. The FeNi electrodes also show a much better stability in the cyclic tests, compared to that of the state‐of‐the‐art Pt/C and Pt/C+Ir/C electrodes for reversible OER and ORR. The high performance is likely due to the significantly enhanced OER activity contributed by the introduction of Ni atoms, forming bridged FeNi bimetallic dual atom active sites for OER. This study provides a new platform for the development of highly active bimetallic atomic catalysts based bifunctional electrocatalysts for metal‐air batteries. The modified one‐pot synthesis methods demonstrated in this study can also be applicable to other atomically dispersed catalysts on CNTs or graphenes.

Electrocatalysis of Oxygen on Bifunctional Nickel‐Cobaltite Spinel

“…However, the high cost of these electrocatalysts makes these materials unattractive. To replace these expensive noble catalysts, low cost alternatives such as transition metal oxides have been considered . Among them, cobalt‐based oxides are envisaged as the most active catalysts for the electrocatalysis of oxygen .…”

Improving the Catalytic Activity of Carbon‐Supported Single Atom Catalysts by Polynary Metal or Heteroatom Doping

“…Few strategies utilize a top–down process. For instance, to contain oxygen groups as adsorbing sites, graphene oxide (GO), [ 71 ] and oxidized carbon nanotubes [ 38 ] were used as the carbon‐supports to prepare PdCu–reduced graphene oxide (rGO) by co‐reduction of GO/metal ions, and FeNi‐carbon nanotubes (CNTs) SACs by constructing N–Fe/N–Ni coordination, respectively. The bottom–up strategies can be further divided into one‐pot and post‐synthesis approaches based on the adding order of the target metal ions.…”

“…The onset potential of 1.06 V (relative to RHE), Tafel slope of 66 mV dec −1 , half‐wave potential of 0.863 V in 0.1 m HClO 4 compared to Pt/C of ≈1.03 V, 0.858 V, and 68 mV dec −1 , respectively all point to its improved catalytic performance. [ 77 ] A similar trend in catalytic enhancement of ORR for ZnCo‐NC SACs (Zn–Co atomic pairs coordinated on N, S‐codoped carbon) in 0.1 m KOH [ 50,75 ] in Figure 3b,c, PtCo‐NC SACs (atomic Pt–Co on N‐doped carbon) in 0.1 m KOH, [ 78 ] FeNi‐NC SACs (bimetallic atomically dispersed FeNi on N‐doped carbon nanotube) in 0.1 m KOH, [ 38 ] FeCo‐NC SACs (atomic FeCo decorated on N‐doped carbon) in 0.1 m KOH [ 51 ] have all been reported. Furthermore, PtCu clusters on graphene show high activity for electrocatalysis of N 2 RR, and the yield of NH 3 is up to 2.8 µg h −1 mg −1 higher than that of its monometallic counterparts (Pt, Cu catalyst) in Figure 3d.…”

“…[ 33–35 ] These two strategies are the most straightforward and widely used processes to modulate the catalytic activity, selectivity of metal catalysts, and carbon‐based catalysts, respectively. The polynary metals or polynary heteroatoms doped carbon‐supported SACs show distinctly improved catalytic activity and selectivity in many electrochemical reactions including oxygen reduction reaction (ORR), [ 36 ] carbon dioxide reduction reaction (CO 2 RR), [ 37 ] nitrogen reduction reaction (N 2 RR), [ 37 ] oxygen evolution reaction (OER), [ 38 ] hydrogen evolution reaction (HER), [ 10 ] and CO oxidation. [ 39 ] To the best of our knowledge, there is no Review that summarizes the advancement of polynary metals or polynary heteroatoms carbon‐supported SACs.…”

Deep-Breathing Honeycomb-like Co-Nx-C Nanopolyhedron Bifunctional Oxygen Electrocatalysts for Rechargeable Zn-Air Batteries

“…Hence, oxygen molecules will not be able to reach the active sites inside the carbon matrix ( Hou et al., 2019 ). This phenomenon makes the active sites difficult to “breath,” especially for those buried deep inside ( Liu et al., 2019 ; Cheng et al., 2019a ; Wang et al., 2018c ), corresponding to a very low utilization of active sites. To alleviate this issue, some electrocatalysts with abundant micro/mesopores or interior hollows were synthesized to achieve better mass transport ( Lin et al., 2017 ; Zhong et al., 2018 ).…”