Characterisation of non-uniform functional surfaces: towards linking basic surface properties with electrocatalytic activity

Functional materials, particularly heterogeneous catalysts, are often non-uniform at a microscopic level making their detailed characterisation extremely complex. This complexity inhibits the design and implementation of novel functional materials as such characterisation is a key to understanding interfaces for heterogeneous catalysis. We demonstrate that a combination of Scanning Kelvin Probe (SKP) and Scanning Electrochemical Microscopy (SECM) experiments made over the same sample surface using an integrated SKP–SECM system provides a powerful and robust tool to link basic surface properties with the observed electrocatalytic activity. As the SKP-response can be accurately assessed using modern quantum chemical approaches to benchmark analytical signals for different surface structures with varying compositions, application of an integrated SKP–SECM system can offer valuable insight into the origin of the observed electrocatalytic activity. As model objects, we used Pt(111)-like thin films modified with sub-monolayer and monolayer amounts of Cu atoms located at the electrode surface and in the sub-surface region. The exact position of the Cu atoms relative to the topmost Pt layer greatly affects basic surface properties and governs the electrocatalytic activity of the surface towards various reactions, i.e. the oxygen reduction reaction. SKP–SECM appeared to be a very sensitive tool to monitor those changes as a function of the spatial coordinates.Financial support by the EU and the state NRW in the framework of the HighTech. NRW program is gratefully acknowledged. A.S.B. and W.S. additionally acknowledge financial support in the framework of Helmholtz-Energie-Allianz “Stationäre elektrochemische Speicher und Wandler” (HA-E-0002) and the Cluster of Excellence RESOLV (EXC 1069) funded by the DFG (Deutsche Forschungsgemeinschaft).Published versio

Polybenzoxazine-derived N-doped carbon as matrix for powder-based electrocatalysts

In addition to catalytic activity, intrinsic stability, tight immobilization on a suitable electrode surface, and sufficient electronic conductivity are fundamental prerequisites for the long-term operation of particle- and especially powder-based electrocatalysts. We present a novel approach to concurrently address these challenges by using the unique properties of polybenzoxazine (pBO) polymers, namely near-zero shrinkage and high residual-char yield even after pyrolysis at high temperatures. Pyrolysis of a nanocubic prussian blue analogue precursor (Km Mnx [Co(CN)₆]y⋅nH₂O) embedded in a bisphenol A and aniline-based pBO led to the formation of a N-doped carbon matrix modified with MnxCoyOz nanocubes. The obtained electrocatalyst exhibits high efficiency toward the oxygen evolution reaction (OER) and more importantly a stable performance for at least 65 h

Technoeconomic Analysis of PEC Water Splitting at Various Scales

Hydrogen production via photoelectrochemical (PEC) water splitting represents a promising route to store intermittent solar energy in a versatile chemical energy carrier and could significantly contribute to a future sustainable energy infrastructure. The transition of a technology from the lab to a real plant, i.e. running a plant instead of running an experiment, involves numerous technical and economic aspects which need to be taken into account in order to achieve the final intention: economically viable, ecologically beneficial, and industrially applicable processes. This work refers to technoeconomic findings obtained within the EU project PECDEMO (2014–2017), which addressed hydrogen production in hybrid photoelectrochemical-photovoltaic (PEC-PV) tandem devices. Section 10.2 compiles some practical considerations and boundary conditions relevant for the realisation of extensive hydrogen production by PEC water splitting. Different hydrogen production and application scenarios, which cover a wide range of hydrogen production capacity, are considered

Integrated scanning kelvin probe-scanning electrochemical microscopy system

Ein integriertes System, das auf einer Kelvin-Sonde und einem elektrochemischen Rastermikroskop basiert, wurde entwickelt und aufgebaut. Der Vorteil dieses Systems besteht darin, dass es sequenzielle Experimente im SKP-Modus und unterschiedlichen SECM-Modi mit der gleichen Elektrode und über der gleichen Stelle auf der Probenoberfläche durchführen kann. Die speziell entwickelten "glasfreien" SKP-SECM-Elektroden ermöglichen eine hohe laterale Auflösung. Das System wurde für die Untersuchung eines Sauerstoffreduktions-katalysators, der auf der Oberfläche von einkristallinen Pt-Filmen hergestellt wurde, ange-wendet. Die Korrelation zwischen der Austrittsarbeit und der katalytischen Aktivität der Oberfläche wurde evaluiert. Das Korrosionsverhalten und die $\textit {in-situ}$ Sauerstoffreduktion auf der Oberfläche von synthetisierten $Al_{2}CuMg$-Einzelkristallen wurden mit Hilfe des entwickel-ten Systems mittels SKP und RC-SECM erfolgreich visualisiert und untersucht