Single-atomic cobalt sites embedded in hierarchically ordered porous nitrogen-doped carbon as a superior bifunctional electrocatalyst

Abstract

Exploring efficient and cost-effective catalysts to replace precious metal catalysts, such as Pt, for electrocatalytic oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) holds great promise for renewable energy technologies. Herein, we prepare a type of Co catalyst with single-atomic Co sites embedded in hierarchically ordered porous N-doped carbon (Co-SAS/HOPNC) through a facile dual-template cooperative pyrolysis approach. The desirable combination of highly dispersed isolated atomic Co-N4 active sites, large surface area, high porosity, and good conductivity gives rise to an excellent catalytic performance. The catalyst exhibits outstanding performance for ORR in alkaline medium with a half-wave potential (E1/2) of 0.892 V, which is 53 mV more positive than that of Pt/C, as well as a high tolerance of methanol and great stability. The catalyst also shows a remarkable catalytic performance for HER with distinctly high turnover frequencies of 0.41 and 3.8 s−1 at an overpotential of 100 and 200 mV, respectively, together with a long-term durability in acidic condition. Experiments and density functional theory (DFT) calculations reveal that the atomically isolated single Co sites and the structural advantages of the unique 3D hierarchical porous architecture synergistically contribute to the high catalytic activity.

An Enzyme‐Mimicking Single‐Atom Catalyst as an Efficient Multiple Reactive Oxygen and Nitrogen Species Scavenger for Sepsis Management

“…The XANES curves verified that Co single atoms carried positive charges (Figure e) . The Fourier‐transformed (FT) κ 3 ‐weighted EXAFS spectrum of the Co/PMCS displayed only one main peak around 1.35 Å (Figure f), indicating that the Co atoms were existed as an isolated single atomic site form . The wavelet transform (WT) plot of Co/PMCS demonstrated the WT maximum at 4 Å −1 , which was accordant to the Co−N bonding in comparison with Co foil and Co 3 O 4 (Figure i–k).…”

“…The CUS structure of single Co sites in Co/PMCS was further investigated by synchrotron radiation‐based X‐ray absorption near‐edge structure (XANES) and extended X‐ray absorption fine structure (EXAFS) spectra. The XANES curves verified that Co single atoms carried positive charges (Figure e) . The Fourier‐transformed (FT) κ 3 ‐weighted EXAFS spectrum of the Co/PMCS displayed only one main peak around 1.35 Å (Figure f), indicating that the Co atoms were existed as an isolated single atomic site form .…”

Ultrahigh‐Loading Zinc Single‐Atom Catalyst for Highly Efficient Oxygen Reduction in Both Acidic and Alkaline Media

“…[10] As shown in Zn K-edge XANES spectra (Figure 2a), the position of the absorption threshold for Zn-N-C-1 is close to those of ZnO and ZnPc,t hus indicating that the valence state of zinc species in Zn-N-C-1 is probably + 2. [10] As shown in Zn K-edge XANES spectra (Figure 2a), the position of the absorption threshold for Zn-N-C-1 is close to those of ZnO and ZnPc,t hus indicating that the valence state of zinc species in Zn-N-C-1 is probably + 2.…”

Oxygen Reduction Reactions on Single‐ or Few‐Atom Discrete Active Sites for Heterogeneous Catalysis

“…Inset: Schematic model of Co‐SAS/HOPNC: Co (orange), N (blue), and C (gray). Adapted with permission . Copyright 2018, United States National Academy of Sciences.…”