High Faradaic efficiency and appreciable current density are essential for future applications of the electrochemical CO2 reduction reaction (CO2RR). However, these goals are difficult to achieve simultaneously due to the severe side reaction – the hydrogen evolution reaction (HER). Herein, we successfully synthesized coordinatively unsaturated nickel–nitrogen (Ni–N) sites doped within porous carbon with a nickel loading as high as 5.44 wt% by pyrolysis of Zn/Ni bimetallic zeolitic imidazolate framework-8. Over the Ni–N composite catalysts, the CO current density increases with the overpotential and reaches 71.5 ± 2.9 mA cm−2 at −1.03 V (vs. a reversible hydrogen electrode, RHE), while maintaining a high CO Faradaic efficiency of 92.0–98.0% over a wide potential range of −0.53 to −1.03 V (vs. the RHE). Density functional theory calculations suggest that the CO2RR occurs more easily than the HER over the coordinatively unsaturated Ni–N site. Therefore, highly doped and coordinatively unsaturated Ni–N sites achieve high current density and Faradaic efficiency of the CO2RR simultaneously, breaking current limits in metal–nitrogen composite catalysts.

Coordinatively unsaturated nickel–nitrogen sites towards selective and high-rate CO2 electroreduction

Surface chemistry of porphyrins and phthalocyanines

Carbon materials doped with transition metal and nitrogen are highly active, non-precious metal catalysts for the electrochemical conversion of molecular oxygen in fuel cells, metal air batteries, and electrolytic processes. However, accurate measurement of their intrinsic turn-over frequency and active-site density based on metal centres in bulk and surface has remained difficult to date, which has hampered a more rational catalyst design. Here we report a successful quantification of bulk and surface-based active-site density and associated turn-over frequency values of mono- and bimetallic Fe/N-doped carbons using a combination of chemisorption, desorption and (57)Fe Mossbauer spectroscopy techniques. Our general approach yields an experimental descriptor for the intrinsic activity and the active-site utilization, aiding in the catalyst development process and enabling a previously unachieved level of understanding of reactivity trends owing to a deconvolution of site density and intrinsic activity.

Quantifying the density and utilization of active sites in non-precious metal oxygen electroreduction catalysts.

Thermal degradation mechanisms of PEDOT:PSS

Metal phthalocyanines (MPcs) are versatile conjugated macrocycles that have attracted a great deal of interest as active components in modern organic electronic devices. In particular, the charge transport properties of MPcs, their chemical stability, and their synthetic versatility make them ideal candidate materials for use in organic thin-film transistors (OTFTs). This article reviews recent progress in both the material design and device engineering of MPc-based OTFTs, including the introduction of solubilizing groups on the MPcs and the surface modification of substrates to induce favorable MPc self-assembly. Finally, a discussion on emerging niche applications based on MPc OTFTs will be explored, in addition to a perspective and outlook on these promising materials in OTFTs. The scope of this review is focused primarily on the advances made in the field of MPc-based OTFTs since 2008.

Phthalocyanine-Based Organic Thin-Film Transistors: A Review of Recent Advances

The electronic properties of the interface between cobalt phthalocyanine and gold substrate were investigated by photoexcited electron spectroscopies (UPS, XPS, and XAES). The experimental data indicate a quite strong interaction between the organic molecules and the metallic substrate, which is concluded from the different shape of the XPS Co 2p and Co LVV Auger spectral lines, as well as a splitting of the HOMO in the UP spectra. Initial and final state effects in photoemission and a possible change of the crystal field symmetry at the interface are discussed.

Electronic Structure of Co-Phthalocyanine on Gold Investigated by Photoexcited Electron Spectroscopies: Indication of Co Ion−Metal Interaction

The electronic structure of iron phthalocyanine (FePc) and interface properties on Ag(111) and Au(100) are investigated by photoexcited electron spectroscopies: photoemission (XPS and UPS) and X-ray absorption spectroscopy (XAS or NEXAFS) Valence band structures with Fe character were identified using resonant photoemission The strength and nature of the interaction at the interface depend clearly on the substrate A strong interaction of the central metal atom of the phthalocyanine occurs on Ag(111), whereas no significant changes of the electronic situation were found for FePc on Au(100) Resonant photoemission data show that for FePc on Ag(111) the formed interface states close to the Fermi level are determined by the interaction between Fe 3d states and substrate related states On the other hand, also the nitrogen atom of FePc is involved in the interaction

Electronic Structure of FePc and Interface Properties on Ag(111) and Au(100)

The electronic structure of Ni-phthalocyanine/metal interfaces studied by X-ray and ultraviolet photoelectron spectroscopy

X-ray absorption (XAS) and photoemission (XPS) spectroscopy revealed a strong interaction at the interface between transition-metal Cobalt phthalocyanine (CoPc) and single-crystalline Ag(111) substrate. According the Co L-edge absorption spectra of ultrathin CoPc films, charge transfer between the metal 3d electrons and the underlying metallic substrate occurs. Less intense but comparable effects are also observed at the MnPc/Ag(111) interface for partially filled d levels of Mn. The nature of interacting orbitals is also discussed by means of resonant photoemission spectroscopy (ResPES) as well as in comparison with the CoPc/Au(100) interface studied previously.

F. Petraki

Papers

Electronic Structure of Co-Phthalocyanine on Gold Investigated by Photoexcited Electron Spectroscopies: Indication of Co Ion−Metal Interaction

Electronic Structure of FePc and Interface Properties on Ag(111) and Au(100)

The electronic structure of Ni-phthalocyanine/metal interfaces studied by X-ray and ultraviolet photoelectron spectroscopy

Impact of the 3d Electronic States of Cobalt and Manganese Phthalocyanines on the Electronic Structure at the Interface to Ag(111)

Charge transfer between transition metal phthalocyanines and metal substrates: The role of the transition metal