Atomically Dispersed Zn‐Pyrrolic‐N₄ Cathode Catalysts for Hydrogen Fuel Cells

Abstract

To achieve practical application of fuel cell, it is vital to develop highly efficient and durable Pt-free catalysts. Herein, we prepare atomically dispersed ZnNC catalysts with Zn-Pyrrolic-N 4 moieties and abundant mesoporous structure. The ZnNC-based anionexchange membrane fuel cell (AEMFC) presents an ultrahigh peak power density of 1.63 and 0.83 W cm À 2 in H 2 -O 2 and H 2 -air (CO 2 -free), and also exhibits long-term stability with more than 120 and 100 h for H 2 -air (CO 2free) and H 2 -O 2 , respectively. Density functional calculations further unveil that the Zn-Pyrrolic-N 4 structure is the origin of high activity of as-synthesized ZnNC catalyst, while the Zn-Pyridinic-N 4 moiety is inactive for oxygen reduction reaction (ORR), which successfully explain the puzzle why most Zn-metal-organic framework -derived ZnNC catalysts in previous reports did not present good ORR activity because of their Zn-Pyridinic-N 4 moieties. This work offers a new route for speeding up development of AEMFCs.

Long-Range Regulation of Se Doping for Oxygen Reduction of Atomically Dispersed Sb Catalysts for Ultralow-Temperature Solid-State Zn–Air Batteries

“…Interestingly, Sb–SeNC also exhibits an apparently larger BET SSA (1738 m 2 g –1 ) than Sb–NC (1188 m 2 g –1 ) and Se–NC (1251 m 2 g –1 , Figure f), accompanying abundant micropores, mesopores, and macropores (Figures g and S8), which is attributed to the two-step pyrolysis of Sb–SeNC, while it is one-step pyrolysis for both Sb–NC and Se–NC. Two-step pyrolysis is beneficial for the formation of hierarchical porous structures that expose more active sites and facilitate mass transport in ORR. , The X-ray diffractions (XRDs) in Figure S9 also show that all three samples only present two broad peaks at around 25 and 44°, indicating the absence of Sb and Se nanoparticles (NPs) and their compounds. − …”

“…Two-step pyrolysis is beneficial for the formation of hierarchical porous structures that expose more active sites and facilitate mass transport in ORR. 12,19 The X-ray diffractions (XRDs) in Figure S9 also show that all three samples only present two broad peaks at around 25 and 44°, indicating the absence of Sb and Se nanoparticles (NPs) and their compounds. 41−43 The N 1s X-ray photoelectron spectroscopy (XPS) spectrum of Sb−SeNC in Figure S10 can be easily deconvoluted into five peaks, including pyridine N (398.3 eV), Sb−N (399.1 eV), pyrrolic N (400.1 eV), graphitic N (401.5 eV), and N-oxide (403.1 eV) species.…”

“…The atom-dispersed M–N–C catalyst exhibits excellent ORR activity comparable to Pt-based catalysts, mainly due to its adjustable electronic structure and maximum atomic utilization, and is recognized as the most promising alternative to Pt-based catalysts. − It is reported that atom-dispersed catalysts anchored on N-doped carbon also exhibit excellent performance in LT-ZAB . Cui et al obtained a highly active ORR catalyst containing Fe–N 4 and Mn–N 4 structures, and the PPD of the catalyst-based flexible ZAB reached 30 mW cm –2 at −40 °C, and the rate discharge stability remained at 12 h .…”

Regulating the electronic structure of single-atom catalysts for electrochemical energy conversion

“…For atomically dispersed Zn–N–C SACs, the Zn-pyrrolic-N 4 structure is the origin of high catalytic activity. 172 Specifically, the binding strength of Zn to O with the pyrrole N coordination is lower than that of the pyridine N coordination, leading to the weaker adsorption of oxygen species at Zn sites, thus increasing the intrinsic ORR activity (Fig. 8j).…”

Strain Engineering of the NiTe/Ni2P Heterostructure to Boost the Oxygen Evolution Reaction

“…Water splitting to produce hydrogen and oxygen has been considered one of the most promising ways to alleviate the energy crisis and prevent worsening environmental problems. Water splitting includes two half reactions, the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). − Due to the sluggish kinetics caused by the multistep four-electron redox process, a higher overpotential, for which precious metal Ru- or Ir-based catalysts have been used, is needed to drive the OER compared to the HER. − However, precious metal catalysts suffer from the disadvantages of high price, low content, and poor OER stability, which seriously limit their practical applications. − Therefore, discovering high-performance non-precious metal (NPM) catalysts for the OER is an extremely important research direction. − …”