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To meet increasing requirement for innovative energy storage and conversion technology, it is urgent to prepare effective, affordable, and long-term stable oxygen electrocatalysts to replace precious metal-based counterparts. Herein, a two-step pyrolysis strategy is developed for controlled synthesis of Fe 2 O 3 and Mn 3 O 4 anchored on carbon nanotubes/nanosheets (Fe 2 O 3 -Mn 3 O 4 -CNTs/NSs). The typical catalyst has a high half-wave potential (E 1/2 = 0.87 V) for oxygen reduction reaction (ORR), accompanied with a smaller overpotential (η 10 = 290 mV) for oxygen evolution reaction (OER), showing substantial improvement in the ORR and OER performances. As well, density functional theory calculations are performed to illustrate the catalytic mechanism, where the in situ generated Fe 2 O 3 directly correlates to the reduced energy barrier, rather than Mn 3 O 4 . The Fe 2 O 3 -Mn 3 O 4 -CNTs/NSs-based Zn-air battery exhibits a high-power density (153 mW cm -2 ) and satisfyingly long durability (1650 charge/discharge cycles/550 h). This work provides a new reference for preparation of highly reversible oxygen conversion catalysts., (© 2024 Wiley‐VCH GmbH.)

Transition metal catalysts are regarded as one of promising alternatives to replace traditional Pt-based catalysts for oxygen reduction reaction (ORR). In this work, an efficient ORR catalyst is synthesized by confining Fe 3 C nanoparticles into N, S co-doped porous carbon nanosheets (Fe 3 C/N,S-CNS) via high-temperature pyrolysis, in which 5-sulfosalicylic acid (SSA) demonstrates as an ideal complexing agent for iron (ΙΙΙ) acetylacetonate while g-C 3 N 4 behaves as a nitrogen source. The influence of the pyrolysis temperature on the ORR performance is strictly examined in the controlled experiments. The obtained catalyst exhibits excellent ORR performance (E 1/2  = 0.86 V; E onset  = 0.98 V) in alkaline electrolyte, coupled by exhibiting the superior catalytic activity and stability (E 1/2  = 0.83 V, E onset  = 0.95 V) to Pt/C in acidic media. In parallel, its ORR mechanism is carefully illustrated by the density functional theory (DFT) calculations, especially the role of the incorporated Fe 3 C played in the catalytic process. The catalyst-assembled Zn-air battery also exhibits a much higher power density (163 mW cm -2 ) and ultralong cyclic stability in the charge-discharge test for 750 h with a gap increase down to 20 mV. This study provides some constructive insights for preparation of advanced ORR catalysts in green energy conversion units correlated systems., (© 2023 Wiley-VCH GmbH.)

It is a challenging task to research oxygen reduction electrocatalysts with cost-effectiveness, high-performance and ultra-stability to replace traditional noble metal catalysts in renewable energy conversion/storage devices. Herein, cobalt phosphide (Co 2 P) nanoparticles encapsulated in Mn, N co-doped porous carbon nanosheets with abundant nanoholes (Co 2 P/Mn,N-PCNS) were prepared by a alizarin complexone coordination regulated pyrolysis at 800 °C. In the controlled experiments, the pyrolysis temperature and metal types were investigated in details. The resultant catalyst exhibited rapid mass/charge transfer and superior oxygen reduction reaction (ORR) performance (E onset  = 0.96 V; E 1/2  = 0.86 V vs RHE), surpassing commercial Pt/C. This work presents some constructive guidelines for synthesis of appealing ORR electrocatalysts in renewable energy technology., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Developing efficient and highly low-cost electrocatalysts for oxygen reduction reaction (ORR) is highly desirable and challenging for renewable energy devices. In this work, a novel sandwich-like heterostructured nanocomposite was facilely constructed via incorporation of Co 9 S 8 nanoclusters/Co 3 [Co(CN) 6 ] 2 nanocubes in N,S-doped carbon multilayers (Co 9 S 8 /Co 3 [Co(CN) 6 ] 2 /N,S-CMLs) by a one-pot coordination-modulated pyrolysis of a mixture containing dicyandiamide, Co(NO 3 ) 2 and Evans blue at 800 °C. The control tests demonstrated critical roles of the pyrolysis temperature played on the final morphology and shape, and discussed the formation mechanism in detail. The as-prepared catalyst exhibited appealing electrocatalytic performance for ORR with a more positive onset potential (E onset  = 0.96 V vs. RHE) and half-wave potential (E 1/2  = 0.87 V vs. RHE) in 0.1 M KOH electrolyte, far outperforming other home-made catalysts and commercial Pt/C. This work opens a new avenue to prepare efficient, cost-effectiveness and stable electrocatalysts in sustainable energy storage and conversion devices., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Nitrogen- and transition metal-dual doped carbon materials with low cost and high catalytic performances are considered as one of promising alternatives for noble metal catalysts in acceleration of oxygen reduction reaction (ORR). In this work, three-dimensional (3D) self-supporting superstructures of iron carbide (Fe 3 C) nanoclusters entrapped in manganese (Mn)- and nitrogen (N)-dual doped carbon nanosheets covered with double-sided nanoneedles carbon arrays (Fe 3 C/Mn,N-NCAs) are simply synthesized by a coordination pyrolysis method, in which dicyandiamide mainly behaves as nitrogen source and 1-(2-pyridylazo)-2-naphthol (PAN) as carbon source. Integration of the unique 3D self-supporting superstructures and synergistic effects of the multi-compositions, the as-obtained catalyst displays appealing ORR performance such as the much positive onset potential (E onset  = 0.98 V vs. RHE) and half-wave potential (E 1/2  = 0.88 V vs. RHE), as well as a just 10 mV negative shift in E 1/2 after 2000 cycles, surpassing commercial Pt/C. This work provides some valuable perspectives for preparation of high-efficiency and low-cost non-noble metal ORR electrocatalysts in energy transformation and storage correlated systems., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)