Theoretically Revealed and Experimentally Demonstrated Synergistic Electronic Interaction of CoFe Dual-Metal Sites on N-doped Carbon for Boosting Both Oxygen Reduction and Evolution Reactions

Abstract

Heteronuclear double-atom catalysts, unlike single atom catalysts, may change the charge density of active metal sites by introducing another metal single atom, thereby modifying the adsorption energies of reaction intermediates and increasing the catalytic activities. First, density functional theory calculations are used to figure out the best combination by modeling two transition-metal atoms from Fe, Co, and Ni onto N-doped graphene. Generally, Fe and Co sites are highly active for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), respectively. The combination of Co and Fe to form CoFe–N–C not only further improves the Fe’s ORR and Co’s OER activities but also greatly enhances the Co site’s ORR and Fe site’s OER activities. Then, we synthesize the CoFe–N–C by a two-step pyrolysis process and find that the CoFe–N–C exhibits exceptional ORR and OER electrocatalytic activities in alkaline media, significantly superior to Fe–N–C and Co–N–C and even commercial catalysts.

Highly Efficient Electrocatalytic Oxygen Evolution Over Atomically Dispersed Synergistic Ni/Co Dual Sites

“…The impressive OER activity and kinetics thus render a-NiCo/NC one of the most efficient SACs towards OER in alkaline medium (Table S2, Support-ing Information). [19,25,26,[36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] To further elucidate the intrinsic mechanism for the enhancement of OER activity, per-site turnover frequency (TOF) is calculated based on the assumption that all metal atoms are active sites. Figure 4d shows the enhanced intrinsic activity in a-NiCo/NC with an average five-fold improvement compared to a-Ni/NC and a-Co/NC at the overpotentials from 250 to 325 mV.…”

“…As shown in Figure 4c, the a‐NiCo/NC sample exhibits the smallest Tafel slope of 49 mV dec −1 . The impressive OER activity and kinetics thus render a‐NiCo/NC one of the most efficient SACs towards OER in alkaline medium (Table S2, Supporting Information) [19, 25, 26, 36–50] . To further elucidate the intrinsic mechanism for the enhancement of OER activity, per‐site turnover frequency (TOF) is calculated based on the assumption that all metal atoms are active sites.…”

Tailoring of Active Sites from Single to Dual Atom Sites for Highly Efficient Electrocatalysis

“…(a-d) Schematic presentation for the formation of Fe–Co, Fe–Mn, Pt–Ru, and Ni–Fe heteronuclear DACs. ,,, Fourier-transformed EXAFS spectra of (e) Fe K-edge after activation and (f) Co K-edge of Co–N–C with various durations in the OER . (g, h) DFT calculation results on M 2 N 6 DACs for the ORR overpotential versus Δ G *OOH and the OER overpotential versus adsorption free energy difference (Δ G *OOH – Δ G *O) . (a) Reproduced with permission from ref .…”

Regulating the coordination environment of a metal–organic framework for an efficient electrocatalytic oxygen evolution reaction

“…52–54 The latter is more challenging, 55 and the electrocatalytic performance of MOFs needs to be enhanced to the next level. 56…”

“…[52][53][54] The latter is more challenging, 55 and the electrocatalytic performance of MOFs needs to be enhanced to the next level. 56 To deal with the above challenges, we have synthesized a bimetal-organic framework (FeCo-L 1 L 2 ) using a simple and cost-effective solvothermal method using the free assembly of Fe and Co ions with 2,5-dihydroxyterephthalic acid (defined as L 1 ) and 4,6-dihydroxyisophthalic acid (defined as L 2 ). The synthetic strategy is shown in Scheme 1.…”