Aerogel is introduced as an OER catalyst substrate for PEM electrolyzer and shows superior activity.

The abundance of available surface chemical information and edge structures of carbon materials have attracted tremendous interest in catalysis. For the oxygen evolution reaction (OER), the edge effects of carbon materials have rarely been studied in detail because of the complexity of various coexisting edge configurations and the controversy between carbon corrosion and carbon catalysis. Herein, the exact roles of common carbon active edge sites in the OER were interrogated using polycyclic aromatic hydrocarbons (PAHs) with designated configurations (zigzag and armchair) as model probe molecules, with a focus on structure–function relationships. Zigzag configurations of PAHs showed high activity for the OER while also showing a good stability at a reasonable potential. They show a TOF value of 0.276 s −1 in 0.1 m KOH. The catalytic activity of carbon edge sites was further effectively regulated by extending the π conjugation structure at a molecular level.

The recent mechanistic understanding of active sites, adsorbed intermediate products, and rate‐determining steps (RDS) of nitrogen (N)‐modified carbon catalysts in electrocatalytic oxygen reduction (ORR) and oxygen evolution reaction (OER) are still rife with controversy because of the inevitable coexistence of diverse N configurations and the technical limitations for the observation of formed intermediates. Herein, seven kinds of aromatic molecules with designated single N species are used as model structures to investigate the explicit role of each common N group in both ORR and OER. Specifically, dynamic evolution of active sites and key adsorbed intermediate products including O2 (ads), superoxide anion O2−*, and OOH* are monitored with in situ spectroscopy. We propose that the formation of *OOH species from O2−* (O2−*+H2O→OOH*+OH−) is a possible RDS during the ORR process, whereas the generation of O2 from OOH* species is the most likely RDS during the OER process.

Cobalt oxide (assigned as CoO x ) is an efficient oxygen evolution reaction (OER) nanocatalyst, which has been extensively studied as a replacement to noble metal-based catalysts. The recent observations and understandings for the interfacial state, adsorbed intermediate products, and rate-determining steps (RDS) on CoO x , however, have remained elusive because of the dynamic transformation of different Co ions and the transient nature of the intermediates formed during the OER process. In this work, we propose that under the chosen experimental conditions, the redox process between Co­(III) and Co­(IV) species does not follow a proton-coupled electron transfer mechanism that is thought to be common prior to the OER, but it involves a proton-decoupled electron transfer, clarified by isotope labeling experiments and in situ electrostatic modulation. The interfacial state of CoO x is negatively charged prior to the formation of Co­(IV)O species. The theoretical concentration of the resulting Co­(IV)O species is approximately 0.1229 × 1019 cm–2. The Co­(IV)O species are demonstrated to directly regulate the OER performance. Moreover, we experimentally monitor the dynamic evolution behaviors of Co­(IV)O, Co­(O)­O–, OOH*, and O2 –* intermediates during the OER with in situ time-resolved infrared spectroscopy, and the following elementary step OOH* + OH– → OO–* + H2O is likely to be the unexpected RDS in the OER process.

No abstract

Das mechanistische Verständnis der aktiven Zentren, adsorbierten Zwischenprodukte und geschwindigkeitsbestimmenden Schritte (RDS) von N‐modifizierten Kohlenstoffkatalysatoren in der elektrokatalytischen Sauerstoffreduktion (ORR) und der Sauerstoffentwicklung (OER) ist wegen der unvermeidlichen Koexistenz verschiedener N‐Konfigurationen und der technischen Beschränkungen bei der Beobachtung gebildeter Zwischenprodukte noch immer umstritten. Hier werden sieben Arten aromatischer Moleküle mit je einer einzelnen N‐Spezies als Modellstrukturen verwendet, um die explizite Rolle jeder üblichen N‐Gruppe bei der ORR sowie der OER zu untersuchen. Insbesondere wird die dynamische Entwicklung der aktiven Zentren und der wichtigsten adsorbierten Zwischenprodukte einschließlich O2(ads), Superoxidanion O2−* und OOH* mit In‐situ‐Spektroskopie beobachtet. Wir schlagen vor, dass die Bildung von *OOH‐Spezies aus O2−* (O2−*+H2O→OOH*+OH−) ein möglicher RDS während des ORR‐Prozesses ist, da die Erzeugung von O2 aus OOH*‐Spezies der wahrscheinlichste RDS während des OER‐Prozesses ist.

The oxygen evolution reaction (OER) is one of the bottlenecks of electrochemical water splitting. Metal‐free carbons from biomass are highly abundant and can be easily synthesized. Their low price, high conductivity and functionalization makes them promising materials. Herein, we report about free‐standing carbon electrodes as electrocatalysts for the OER. In contrast to powder‐based catalysts, free‐standing electrodes not only avoid additives, but also facilitate post analysis and better reflect industrial conditions. Here, the performance of pure carbon electrodes is compared to those of N‐functionalized ones. Utilizing several analytical techniques, the difference in performance can be rationalized by physical properties. Especially, the analysis of the gaseous products is shown to be of crucial importance. It reveals that N‐doped carbons generate more oxygen and are more robust against carbon corrosion. This illustrates the importance of measuring selectivity especially for carbon electrocatalysts, as higher currents do not necessarily result in higher catalytic activity.

Die reichlichv orhandenen oberflächenchemischen Informationen und Kantenstrukturen von Kohlenstoffmaterialien haben ein enormes Interesse auf dem Gebiet der Katalyse geweckt. Fürdie Sauerstoffentwicklungsreaktion (OER) wurden die Kanteneffekte von Kohlenstoffmaterialien aufgrund verschiedener nebeneinander existierender Kantenkonfigurationen selten im Detail untersucht. Zudem besteht eine Kontroverse zwischen Kohlenstoffkorrosion und Kohlenstoffkatalyse.z wischen Kohlenstoffkorrosion und Kohlenstoffkatalyse selten im Detail untersucht. Hier werden die genauen Rollen der gemeinsamen Kohlenstoff-Aktivkanten in der OER unter Verwendung von polyzyklischen aromatischen Kohlenwasserstoffen (PAKs) mit spezifischen Konfigurationen (Zickzack und Sessel) als Modelltestmoleküle mit dem Fokus auf Struktur-Eigenschafts-Beziehungen untersucht. Zickzackkonfigurationen von PAKs wurden so bestimmt, dass sie eine hohe Aktivitätfürdie OER und zugleich eine gute Stabilitätbei einer angemessenen Spannung aufweisen. Es wurdemit einem TOF-Wert von 0.276 s À1 in 0.1m KOHg earbeitet. Die kataly-tischeAktivitätvon Kohlenstoffkantenstellen konnte durch die Erweiterung ihrer p-Konjugationsstruktur auf molekularer Ebene weiter effektiv reguliert werden.