Single Fe Atom on Hierarchically Porous S, N‐Codoped Nanocarbon Derived from Porphyra Enable Boosted Oxygen Catalysis for Rechargeable Zn‐Air Batteries

Abstract

Iron–nitrogen–carbon materials (Fe–N–C) are known for their excellent oxygen reduction reaction (ORR) performance. Unfortunately, they generally show a laggard oxygen evolution reaction (OER) activity, which results in a lethargic charging performance in rechargeable Zn–air batteries. Here porous S‐doped Fe–N–C nanosheets are innovatively synthesized utilizing a scalable FeCl3‐encapsulated‐porphyra precursor pyrolysis strategy. The obtained electrocatalyst exhibits ultrahigh ORR activity (E1/2 = 0.84 V vs reversible hydrogen electrode) and impressive OER performance (Ej = 10 = 1.64 V). The potential gap (ΔE = Ej = 10 − E1/2) is 0.80 V, outperforming that of most highly active bifunctional electrocatalysts reported to date. Furthermore, the key role of S involved in the atomically dispersed Fe–Nx species on the enhanced ORR and OER activities is expounded for the first time by ultrasound‐assisted extraction of the exclusive S source (taurine) from porphyra. Moreover, the assembled rechargeable Zn–air battery comprising this bifunctional electrocatalyst exhibits higher power density (225.1 mW cm−2) and lower charging–discharging overpotential (1.00 V, 100 mA cm−2 compared to Pt/C + RuO2 catalyst). The design strategy can expand the utilization of earth‐abundant biomaterial‐derived catalysts, and the mechanism investigations of S doping on the structure–activity relationship can inspire the progress of other functional electrocatalysts.

CeO2 Encapsulated by Iron, Sulfur, and Nitrogen‐Doped Carbons for Enhanced Oxygen Reduction Reaction Catalytic Activity

“…The peak of FeS observed in CeO 2 @Fe,S,N−C is possibly formed by the reaction between the active Fe 3+ ions and SDBS (S source) during the pyrolysis process as mentioned above, which can reduce the conductivity and promote the consumption of oxygen . Furthermore, four peaks can be separated from the high resolution Fe 2p spectrum (Figure f), which correspond to Fe 2+ (710.9 eV for Fe 2+ 2p 3/2 and 723.6 for Fe 2+ 2p 3/2 eV) and Fe 3+ (716.3 eV for Fe 3+ 2p 3/2 and 730.0 eV for Fe 3+ 2p 1/2 ) species, that could also participate in the formation of FeN x active sites by bonding with pyridine N …”

“…The different binding states of N, S, C, and O atoms and the valence information of Fe are readily detected in the full XPS spectrum. The high‐resolution N 1s spectrum (Figure b) can be divided into five peaks including pyridine‐N (∼398.1 eV), pyrrole‐N (∼399.0 eV), graphite‐N (∼399.3 eV), Fe−N (∼400.01 eV) and oxygen N (∼404.3 eV) . Graphitic‐N and pyridinic‐N are generally considered to greatly improve the ORR catalytic performance electrocatalytic activity .…”

“…The chemical composition of the CeO 2 @Fe,S,NÀ C NPs is evaluated based on the XPS analysis ( Figure 3b . [22] Graphitic-N and pyridinic-N are generally considered to greatly improve the ORR catalytic performance electrocatalytic activity. [23] According to the result of calculating the fitted area, the content of graphite N and pyridine-N in CeO 2 @Fe,S,NÀ C catalyst is approximately to be 69.94 % and 17.59 %.…”

Engineering Local Coordination Environments of Atomically Dispersed and Heteroatom‐Coordinated Single Metal Site Electrocatalysts for Clean Energy‐Conversion

“…B‐doping was found to simultaneously promote ORR and OER activities of CoN x based catalysts, but the involved mechanism remains elusive due to complexities related to the possible activity of B‐doped C sites. Improving the ORR/OER activity of FeN x by S‐doping has also been reported, where S‐doping simultaneously improved both the ORR and OER activity . The CN − treated catalyst showed an obvious decrease in OER activity, indicating the predominant role of S‐doped FeN x sites for the OER.…”

“…Some N‐coordinated SACs, which have demonstrated bifunctional ORR/OER activities, can serve as effective electrocatalysts for reversible alkaline fuel cells and rechargeable metal–air batteries. Several CoN x , FeN x , B‐doped CoN x , S‐doped FeN x , and Co–FeN x based bifunctional SACs supported on N‐doped porous carbon have been developed and studied for bifunctional ORR/OER applications in fuel cells and batteries. For example, uniformly dispersed CoN 4 sites with a Co loading of ≈15.3 wt% has been achieved by pyrolysis of KCl wrapped ZIF‐67 MOFs .…”