Understanding the Activity of Co‐N_4−xC_x in Atomic Metal Catalysts for Oxygen Reduction Catalysis

Abstract

Atomic metal catalysis (AMC) provides an effective way to enhance activity for the oxygen reduction reaction (ORR). Cobalt anchored on nitrogen‐doped carbon materials have been extensively reported. The carbon‐hosted Co‐N4 structure was widely considered as the active site; however, it is very rare to investigate the activity of Co partially coordinated with N, for example, Co‐N4−xCx. Herein, the activity of Co‐N4−xCx with tunable coordination environment is investigated as the active sites for ORR catalysis. The defect (di‐vacancies) on carbon is essential for the formation of Co‐N4−xCx. N species play two important roles in promoting the intrinsic activity of atomic metal catalyst: N coordinated with Co to manipulate the reactivity by modification of electronic distribution and N helped to trap more Co to increase the number of active sites.

Enantioselective Activity of Hemin in Supramolecular Gels Formed by Co‐Assembly with a Chiral Gelator

“…Xu and his co-workers mixed hemin with two simple derivatives of amino acid, and then formed a hydrogel which can effective minimize the dimerization and oxidative degradation of free hemin in the peroxidization reaction. [7] Hemin immobilized in this hydrogel exhibited higher stability and catalytic activity towards pyrogallol. Shi and his co-workers constructed a hemin-micelle hydrogel complex system as an artificial enzyme, which is the first example with both catalytic activity and substrate selectivity.…”

“…This is also consistent with previous reports on the literature. [7,12,23] Based on the bilayer packing and CD spectra of the co-assemblies, we infer that hemin molecules also are arranged into a helix and exist in a chiral microenvironment, as shown in Figure 6. Obviously, this structure is beneficial to inhibit the formation of bihemin which can improve the catalytic activity of hemin.…”

“…[13] The histidine moiety in LHC18 or DHC18 avoid introducing extra pristine histidine in gel system which was reported previously to further improve hemin activity. [7] And during formation gels, helical structures were obtained through hemin co-assemble with gelators LHC18 and DHC18, as shown in Figure 1. The hemin will be located at a chiral microenvironment, which may be favorable for enantiomeric catalysis.…”

A light-responsive multienzyme complex combining cascade enzymes within a peptide-based matrix

“…The free hemin in PBS demonstrated a broad Soret peak at 346-400 nm, suggesting a mixture of inactive dimeric hemin and active monomeric hemin. 12 Unlike in PBS, the methanol-dissolved hemin displays a single Soret band at 400 nm, which corresponds to monomeric hemin. Compared with free hemin in PBS and methanol, the spectrum of hemin in PepM is similar to that in methanol, indicating that most of hemin is in the monomeric form in GOx&hemin@PepM.…”

“…10,11 In addition, the obtained supramolecular structure also provides a protein-like microenvironment that can facilitate biomimetic applications. [12][13][14] Cascade enzyme systems containing oxidases (such as glucose oxidase, urate oxidase and amino acid oxidase) and catalases are widely used in disease diagnoses, food processing and chemical synthesis. [15][16][17][18] In this study, we created a novel light-responsive multienzyme complex (GOx&hemin@PepM) by incorporating glucose oxidase (GOx) and hemin within the azobenzene modied peptide-based matrix (PepM).…”