Nature uses Fe porphyrin sites for the oxygen reduction reaction (ORR). Synthetic Fe porphyrins have been extensively studied as ORR catalysts, but activity improvement is required. On the other hand, Fe porphyrins have been rarely shown to be efficient for the oxygen evolution reaction (OER). We herein report an enzyme‐inspired Fe porphyrin 1 as an efficient catalyst for both ORR and OER. Complex 1, which bears a tethered imidazole for Fe binding, beats imidazole‐free analogue 2, with an anodic shift of ORR half‐wave potential by 160 mV and a decrease of OER overpotential by 150 mV to get the benchmark current density at 10 mA cm−2. Theoretical studies suggested that hydroxide attack to a formal FeV=O form the O−O bond. The axial imidazole can prevent the formation of trans HO‐FeV=O, which is less effective to form O−O bond with hydroxide. As a practical demonstration, we assembled rechargeable Zn‐air battery with 1, which shows equal performance to that with Pt/Ir‐based materials.
The role that alkyl chain packing density in a self-assembled monolayer (SAM) plays in the adsorption
of protein to the SAM surface was investigated using in situ neutron reflectivity (NR) and total internal
reflection fluorescence (TIRF) measurements of the adsorption behavior of human serum albumin (HSA)
and human immunoglobulin G (HGG). The proteins differ particularly in the fact that HSA has specific
binding pockets for alkyl chains while HGG does not. NR results show that HSA adsorbs from a 1.0 mg/mL
solution as a single layer on the SAMs, with the protein interpenetrating into a less densely packed SAM,
but not into a more densely packed SAM. Likewise, the kinetics of the HSA adsorption to the SAMs varies
markedly with the alkyl chain packing. In contrast, both the structure of the adsorbed layer and adsorption
kinetics vary little with the alkyl chain packing density in the case of HGG adsorbing from solution. HGG
also does not penetrate into loosely packed SAMs. NR results reveal that the HGG adsorbs as two layers,
with the layer closest to the SAM being more tightly packed. When HSA and HGG compete for adsorption
sites on a SAM, HGG effectively displaces HSA from a tightly packed SAM, but does not compete effectively
with HSA adsorbed tenaciously onto a loosely packed SAM.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.