Mechanistic insight into the active centers of single/dual-atom Ni/Fe-based oxygen electrocatalysts

Abstract

Single-atom catalysts with maximum metal utilization efficiency show great potential for sustainable catalytic applications and fundamental mechanistic studies. We here provide a convenient molecular tailoring strategy based on graphitic carbon nitride as support for the rational design of single-site and dual-site single-atom catalysts. Catalysts with single Fe sites exhibit impressive oxygen reduction reaction activity with a half-wave potential of 0.89 V vs. RHE. We find that the single Ni sites are favorable to promote the key structural reconstruction into bridging Ni-O-Fe bonds in dual-site NiFe SAC. Meanwhile, the newly formed Ni-O-Fe bonds create spin channels for electron transfer, resulting in a significant improvement of the oxygen evolution reaction activity with an overpotential of 270 mV at 10 mA cm−2. We further reveal that the water oxidation reaction follows a dual-site pathway through the deprotonation of *OH at both Ni and Fe sites, leading to the formation of bridging O2 atop the Ni-O-Fe sites.

Isolating Single and Few Atoms for Enhanced Catalysis

“…[ 99 ] More recently, Patzke and co‐workers provided new experimental and theoretical insight into the OER pathways on NiFe DAC. [ 237 ] Importantly, the environment of the Ni atoms undergoes a dynamic reconstruction under OER conditions, which facilitated the formation of Ni–O–Fe as true active centers for electron transfer, resulting in an improvement of the activity. These findings offered a guide for the rational design of and precise control of highly efficient dual atoms catalysts.…”

Theory‐Guided Regulation of FeN4Spin State by Neighboring Cu Atoms for Enhanced Oxygen Reduction Electrocatalysis in Flexible Metal–Air Batteries

“…Figure 4a shows the polarization curves of NCAG/Fe−Fe, NCAG/Fe−Cu, and commercial Pt/C (20 wt %) in O 2 ‐saturated 0.1 M KOH. Notably, both NCAG/Fe−Cu and NCAG/Fe−Fe exhibit a superb ORR activity with an onset potential ( E onset ) of +1.07 V and half‐wave potential ( E 1/2 ) of +0.94 V for the former and +1.04 V and +0.94 V for the latter (Figure 4b), both clearly outperforming commercial Pt/C (+0.99 V and +0.86 V) and leading transition metal‐based catalysts reported recently [47–53] . Additionally, the fact that NCAG/Fe−Cu displays a 100 mV positive shift of E 1/2 as compared to NCAG/Cu−Cu (Figure S27) indicates that the Fe centers rather than the Cu ones actually act as the active sites, and the remarkably high onset and half‐wave potentials of NCAG/Fe−Cu confirm the high intrinsic activity of the adjacent heteronuclear bimetal sites.…”

Research progress of asymmetrically coordinated single-atom catalysts for electrocatalytic reactions

“…Through reasonable regulation of the active sites of M 1 –N x and M 2 –N x , researchers found that it not only performed well in a certain type of catalytic reaction, but also became a dual-functional electrocatalyst. 119 Kishwar Khan et al proved that anchoring Ni–N 4 and Fe–N 4 sites on the defect-rich nano-carbon carrier can lead to the rearrangement of electron density (Fig. 7).…”