Overall Oxygen Electrocatalysis on Nitrogen‐Modified Carbon Catalysts: Identification of Active Sites and In Situ Observation of Reactive Intermediates

Abstract

The recent mechanistic understanding of active sites, adsorbed intermediate products, and rate‐determining steps (RDS) of nitrogen (N)‐modified carbon catalysts in electrocatalytic oxygen reduction (ORR) and oxygen evolution reaction (OER) are still rife with controversy because of the inevitable coexistence of diverse N configurations and the technical limitations for the observation of formed intermediates. Herein, seven kinds of aromatic molecules with designated single N species are used as model structures to investigate the explicit role of each common N group in both ORR and OER. Specifically, dynamic evolution of active sites and key adsorbed intermediate products including O2 (ads), superoxide anion O2−*, and OOH* are monitored with in situ spectroscopy. We propose that the formation of *OOH species from O2−* (O2−*+H2O→OOH*+OH−) is a possible RDS during the ORR process, whereas the generation of O2 from OOH* species is the most likely RDS during the OER process.

Mechanistic insight into the active centers of single/dual-atom Ni/Fe-based oxygen electrocatalysts

“…The N 1 s spectrum of CNG consists of a broad peak envelope, whose shape closely resembles that of previous N-doped graphitic materials 31 . In particular, two major peaks centered at 398.2 and 400.7 eV, respectively, are ascribed to pyridine- and pyrrole-like nitrogen 32 , 33 , although a wide variety of nitrogen-containing functional groups can also contribute to the N 1 s peak envelope 34 . All the N 1 s spectra of metal-containing samples show variations in terms of the relative intensity of the two major peaks, and a concurrent increase of intensity in the valley between these two peaks.…”

Surface‐Enhanced Raman Spectroscopic Evidence of Key Intermediate Species and Role of NiFe Dual‐Catalytic Center in Water Oxidation

“…can be generated during the OER process. [9] Thel ow relative concentration, short lifetime and weak adsorption of the intermediates doubtlessly increase the difficulty of in situ detection. Nevertheless,Koper et al provided direct spectroscopic evidence of active NiOO À species.…”

Multiple‐Scale Probing of Intrinsic Active Sites and Reaction Kinetics in Processable Cation‐Inserted Nickel Hydroxide Films

“…[ 30 ] In addition, the absorption peak near ≈1400 cm –1 is detected, which could be attributed to the adsorbed O 2 (ads) on the electrode surface. [ 31 ] For CoNi(OH) 2 , the consumption of OH – (∼≈1400 cm –1 ) and adsorption of O 2 (ads) (≈1630 cm –1 ) can also be detected in the infrared spectrum during the electrochemical test. However, a new peak centered at ≈1050 cm –1 corresponds to the appearance of stretching vibration for OO at ≈ 0.1 V. [ 32,33 ] This is due to the formation of M‐OOH during the charging stage (Figure 4j).…”