The molecular structure, electrochemistry, spectroelectrochemistry and electrocatalytic oxygen reduction reaction (ORR) features of two Co II porphyrin-(2.1.2.1) complexes bearing Ph or F 5 Ph groups at the two meso-positions of the macrocycle are examined. Single crystal X-ray analysis reveal a highly bent, nonplanar macrocyclic conformation of the complex resulting in clamp-shaped molecular structures. Cyclic voltammetry paired with UV/Vis spectroelectrochemistry in PhCN/0.1 M TBAP suggest that the first electron addition corresponds to a macrocyclic-centered reduction while spectral changes observed during the first oxidation are consistent with a metal-centered Co II /Co III process. The activity of the clamp-shaped complexes towards heterogeneous ORR in 0.1 M KOH show selectivity towards the 4e À ORR pathway giving H 2 O. DFT first-principle calculations on the porphyrin catalyst indicates a lower overpotential for 4e À ORR as compared to the 2e À pathway, consistent with experimental data.

Elucidating the effects of various structural components on energy-related small molecule activation is of fundamental and practical significance. Herein the inhibition effect of positively charged substituents on the hydrogen evolution reaction (HER) was reported. With the use of Cu porphyrins 1-5 containing different numbers and locations of positively charged substituents, it was demonstrated that their electrocatalytic HER activities significantly decreased when more cationic units were located close to the Cu ion: the i cat /i p (i cat is the catalytic peak current, i p is the one-electron reduction peak current) value decreased from 38 with zero cationic unit to 15 with four closely located cationic units. Inspired by this result, Cu porphyrin 6, with four meso-phenyl groups each bearing a negatively charged para-sulfonic substituent, was designed. With these anionic units, 6 outperformed the other Cu porphyrins for electrocatalytic HER under the same conditions.

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Recent decades have seen an increasing interest for developing highly active and selective electrocatalysts for the oxygen reduction reaction (ORR). The active site environment of cytochrome c oxidases (CcOs), including...

Developing electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is of great importance. Herein, Co tetrakis(pentafluorophenyl)porphyrin (Co-P) and Fe chloride tetrakis(pentafluorophenyl)porphyrin (Fe-P) were loaded on...