Supramolecular Modulation of Molecular Conformation of Metal Porphyrins toward Remarkably Enhanced Multipurpose Electrocatalysis and Ultrahigh‐Performance Zinc–Air Batteries

Abstract

Modulating the intrinsic catalytic activity of molecular catalysts to improve electrocatalytic performance is significant but challenging. Herein, a simple yet effective strategy to induce molecular flattening of Co (III) meso‐tetra (N‐methyl‐4‐pyridyl) porphyrine (Co‐TMPyP) by supramolecular assembly with chemically converted graphene (CCG) via synergistic electrostatic and π–π interactions is reported. This unique variation in molecular conformation leads to a shortened CoN coordination bond and enhanced electron transfer from the porphyrin macrocycle to the metal ion, thereby optimizing the electronic structure of the catalytic active center in Co‐TMPyP molecule. Thus, the flattened Co‐TMPyP on CCG (Co‐TMPyP/CCG) demonstrates remarkable electrocatalytic performance for the oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), and oxygen evolution reaction (OER) simultaneously as a tri‐functional molecular catalyst for the first time with a high half‐wave potential of 0.824 V for ORR and a low overpotential for HER (320 mV) and OER (379 mV) at 10 mA cm–2, respectively, not only much better than the pristine Co‐TMPyP but also among the best results of molecular catalysts in each aspect of ORR, OER, and HER achieved thus far. As a practical demonstration, the Co‐TMPyP/CCG catalyst is used to assemble a rechargeable Zn–air battery, which shows the highest specific capacity (793 mAh g–1) and power density (225.4 mW cm–2) among all molecular catalyst‐based Zn–air batteries ever reported.

Metalloporphyrin-Linked Mercurated Graphynes for Ultrastable CO2 Electroreduction to CO with Nearly 100% Selectivity at a Current Density of 1.2 A cm–2

“…However, the Co K-edge XANES of Hg-CoTPP/NG shifts to the lower energy, located between Hg-CoTPP and CoO, indicating that the valence state of Co in Hg-CoTPP/NG is reduced due to the presence of NG. The EXAFS spectrum of Hg-CoTPP/NG shows a dominant peak at 1.45 Å, which is attributed to the Co–N scattering . But the Co–N peak of Hg-CoTPP/NG is negatively shifted (Δ = 0.05 Å), indicating a reduced bond length of Co–N in Hg-CoTPP/NG. , The EXAFS fitting results further prove that the bond length of Co–N in Hg-CoTPP/NG (1.91 Å) is shorter than that of Co–N in Hg-CoTPP (1.95 Å).…”

“…The Co K-edge XANES spectra of Hg-CoTPP along with the Co foil, CoO, and CoPc references are shown in Figure d. Obviously, the position of the Co K-edge in Hg-CoTPP is almost identical to that of CoPc. , In addition, the pre-edge feature of the Co K-edge XANES spectrum of Hg-CoTPP (at about 7710 eV) arises from the absorption transition from Co 1s to Co 3d . The Fourier transform (FT) k 2 -weighted χ­( k ) function of the EXAFS spectra of Hg-CoTPP (Figure e) shows that Hg-CoTPP displays the main peak at about 1.4 Å attributed to a single Co–N scattering path .…”

Recent Advances in Porphyrin-Based Systems for Electrochemical Oxygen Evolution Reaction

“…Recently, Xu et al provided another effective approach to regulating the catalytic activity of metalloporphyrin via modulating the molecular conformation [ 93 ]. In their study, monolayer Co-TMPyP (for structure, see Figure 14 ) was absorbed onto the surface of chemically converted graphene (CCG).…”

Manipulating the electronic configuration of Fe–N4sites by an electron-withdrawing/donating strategy with improved oxygen electroreduction performance

“…anchored on carbon (M-N-C) materials show remarkable activity, and they are promising candidates to replace Pt. [11][12][13][14] However, M-N-C catalysts still suffer from the dilemma of low metal loading and suboptimal activity, resulting in insufficient catalytic sites and a heavy reaction energy barrier. In this regard, developing a simple method to modulate the electrochemical behavior of M-N-C catalysts to improve their electrocatalytic performance is desired.…”