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The precisely manipulated π–π stacking of the hybrid catalyst favors the specific prediction of the ORR active sites, which are the iron atoms in the form of natural Fe-N 4 that bind preferentially to the oxygen. [Display omitted] Metal macrocycles with well-defined molecular structures are ideal platforms for the in-depth study of electrochemical oxygen reduction reaction (ORR). Structural integrity of metal macrocycles is vital but remain challenging since the commonly used high-temperature pyrolysis would cause severe structure damage and unidentifiable active sites. Herein, we propose a pyrolysis-free strategy to precisely manipulate the exfoliated 2D iron polyphthalocyanine (FePPc) anchored on reduced graphene oxide (rGO) via π–π stacking using facile high-energy ball milling. A delocalized electron shift caused by π–π interaction is firstly found to be the mechanism of facilitating the remarkable ORR activity of this hybrid catalyst. The optimal FePPc@rGO-HE achieves superior half-wave potential (0.90 V) than 20 % Pt/C. This study offers a new insight in designing stable and high-performance metal macrocycle catalysts with well-defined active sites. [ABSTRACT FROM AUTHOR]

Bifunctional catalyst was prepared by one-step pyrolysis of trimetallic ZIF. The obtained catalyst showed excellent charge–discharge stability in rechargeable Zn-air battery. • A facile and effect strategy is proposed for the synthesis of catalyst precursor. • This strategy reduces the adverse effects of the pyrolysis process on the catalyst. • The coexistence of Co NPs and CoFe-N x improves the ORR/OER activity. • The catalyst displays excellent durability as a cathode for Zn-air battery. Searching for high active, low cost and durable catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) remains challenge in developing metal-air battery cathodes. Herein, we proposed a novel bifunctional catalyst derived from the pyrolysis of Co/Fe/Zn trimetallic zeolitic imidazolite framework. The obtained Co@CoFe 0.01 N C catalyst displays desirable activity for both ORR and OER (E 1/2 = 0.844 V, E j=10 = 1.654 V). The Zn-air battery equipped with Co@CoFe 0.01 N C catalyst on the cathode exhibits a high peak power density of 174.1 mW cm−2, which is much superior than that of commercial 20% Pt/C (87.6 mW cm−2). Significantly, the designed Co@CoFe 0.01 N C presents an outstanding stability for over 100 h in rechargeable Zn-air battery. [ABSTRACT FROM AUTHOR]

Transition metal- and N-codoped carbon catalysts with low cost are latent substitutes to Pt-based catalysts in oxygen reduction reaction. However, the variety of N species obtained by pyrolysis often makes the determination of the active site controversial. Here, we design catalyst structures with pyrrolic-N anchored dual metal centers, while the presence of pyrrolic-N avoids the complex and variable structure of the active sites. Theory calculations demonstrate that coupling of the Cu–N 4 single-atom sites is favorable to reduce the reaction energy barrier of pyrrolic-N-type Fe–N 4 active site during the reaction process. Subsequently, the high-purity pyrrolic-N-type iron and copper single-atom catalyst is successfully synthesized to verify the hypothesis. The obtained FeCu–N–C catalyst achieves a half-wave potential of 0.913 V, higher than the 0.839 V of Pt/C. This route may provide new insights for regulating catalytic active sites in high purity pyrrolic-N type catalysts. The introduction of Cu single-atom optimizes the pyrrolic-N-type Fe–N 4 active site of the FeCu–N–C, endowing the catalyst with remarkable ORR activity (E 1/2 = 0.913 V). [Display omitted] • A pyrrolic-N anchors dual metal centers structure is designed. • DFT calculations demonstrate Cu doping can improve the ORR activity of iron sites. • Catalysts with high purity pyrrolic-N are prepared to prove the DFT calculations. • The half-wave potential of the obtained FeCu–N catalyst reaches 0.913 V. • This strategy provides new insights for regulating active sites of ORR. [ABSTRACT FROM AUTHOR]

Sluggish oxygen reduction reaction (ORR) kinetics is the biggest obstacle in the development of metal air batteries. High-efficiency ORR catalysts with low cost are in urgent needs. Herein, we propose a robust Fe–N–C ORR catalyst with highly dispersed Fe-N x active sites on graphitic-N dominated porous carbon. The synchrotron radiation analyses reveal the discrete Fe-N x coordination derived from the Prussian blue (PB) while the graphitic-N doped porous carbon formed by pyrolysis of the polyaniline (PANI). In virtue of their synergistic catalysis, the tailored Fe–N–C catalyst shows a comparable catalytic activity and a better methanol-tolerance than the commercial Pt/C catalyst. The assembled Zn-Air battery demonstrates a specific capacity of 783 mAh g−1 as well as energy density of 917 Wh kg−1 at 10 mA cm−2, and a maximum power density of 112 mW cm−2 at 191 mA cm−2. A robust Fe– N –C ORR catalyst derived from PB-anchored PANI with well-dispersed Fe-N x active sites on graphitic-N dominated porous carbon host shows comparable performance to the commercial Pt/C catalyst. Image 1 [ABSTRACT FROM AUTHOR]

Exploring efficient and durable non-precious metal catalysts for oxygen reduction reaction (ORR) has long been pursued in the field of metal-air batteries, fuel cells, and solar cells. Rational design and controllable synthesis of desirable catalysts are still a great challenge. In this work, a novel approach is developed to tune the morphologies and structures of Fe–N–C catalysts in combination with the dual nitrogen-containing carbon precursors and the gas-foaming agent. The tailored Fe–N 1 /N 2 –C-A catalyst presents gauze-like porous nanosheets with uniformly dispersed tiny nanoparticles. Such architectures exhibit abundant Fe-N x active sites and high-exposure surfaces. The Fe–N 1 /N 2 –C-A catalyst shows extremely high half-wave potential (E 1/2 , 0.916 V vs. RHE) and large limiting current density (6.3 mA cm−2), far beyond 20 wt% Pt/C catalyst for ORR. This work provides a facile morphological and structural regulation to increase the number and exposure of Fe-N x active sites. The tailored Fe–N–C catalyst presents plentiful Fe-N x active sites and highly exposed active surfaces, resulting in an ultra-high ORR activity far beyond the 20 wt% Pt/C catalyst. Image 1 • A novel approach is explored to tune morphology and structure of Fe–N–C catalyst. • The tailored catalyst presents abundant active sites and high exposure surfaces. • The catalyst shows ultrahigh ORR activity, far beyond the commercial Pt/C. [ABSTRACT FROM AUTHOR]

Appropriate adsorption strength and modes of intermediates on catalysts and the reaction kinetic energy barrier directly determine the selectivity and productivity of final products during CO 2 electroreduction. This work systematically reveals the mechanisms for enhanced CO 2 electroreduction on nitrogen-doped Cu 2 O (N-Cu 2 O) catalyst by in-situ surface enhanced Raman spectroscopy (SERS) and theoretical calculation. The introduction of N into Cu 2 O can significantly enhance the CO 2 adsorption capacity, binding strength of key intermediates and increase the local pH value, resulting in two-fold enhancement of CO and C 2 H 4 production as compared to bare Cu 2 O. Meanwhile, the protonation step is promoted, making the formation of COOH· quickly and earlier. Therefore, the adsorbed CO 2 ·- intermediate formation is produced more rapidly, and the rate-determining step is transferred, continually facilitating the electroreduction of CO 2. This study is inspiring in designing high-performance electrocatalysts for CO 2 reduction. [Display omitted] • A facile and fruitful strategy is proposed to prepare superior CO 2 RR catalysts. • N-Cu 2 O catalyst delivers an improvement for C 2 product production. • The reaction mechanism on Cu 2 O and N-Cu 2 O catalysts are revealed. • The function of N doping is profoundly analyzed. [ABSTRACT FROM AUTHOR]