AVS 67 Session LI-TuM1: Tuesday Morning Live Session I: New Frontiers in Interfaces

Platinum is the most used electrocatalyst in electrochemical energy conversion devices such as fuel cells and electrolysers. In this talk I will highlight the recent work of my group on understanding the surface chemistry of platinum in an aqueous electrolyte, by combining single-crystal electrochemistry, density functional theory calculations, ultra-high-vacuum modeling, in situ spectroscopy and in situ electrochemical scanning tunneling microscopy. I will challenge some existing explanations and interpretations of platinum electrochemistry, and show the sometimes surprising surface disordering of platinum that happens at both positive (anodic) and negative (cathodic) potentials.

Control of surface phenomena by powder modification via atomic layer deposition (ALD) for a spectrum of technology applications has made its way to R&D literature. But commercial adoption of ALD powder modification has been perceived as slow and too expensive to consider as a realistic commercial process. Forge Nano has patented, constructed, and demonstrated a high throughput ALD powder manufacturing capability at commercial scale and is commercializing first markets with partners. The manufacturing capability for powder modification with ALD is unlocking new potential for lower-cost integration of ALD into products. We will discuss a cross-comparison of ALD manufacturing type to product application and scaling requirements. For the first time in history, a pathway for ALD-enhanced materials to be rapidly transitioned from lab-scale demonstration to commercial presentation is available for new product development. The scaleup process addresses the stepwise progression to validate engineering and materials requirements to meet the market price demands. We will demonstrate that ALD enabled materials are the state of the art. The manufacturing of consistent materials with ALD modification is a cost-competitive level and now possible. The future of material science and product development for operation at more demanding conditions is enabled by ALD for a variety of applications.

Rechargeable ion batteries such as Li-ion batteries generally consist of a negative electrode, a positive electrode and an ion conducting electrolyte. Today, much of our knowledge about the interactions of these components at surfaces and interfaces comes from post mortem photoelectron spectroscopy (PES) analyses. For these types of measurements, pre-cycled battery electrodes are transferred to the PES instrument to be characterized in UHV conditions.

Using ambient pressure photoelectron spectroscopy (APPES), we now have the possibility to acquire more realistic information about the interplay of electrode and electrolyte since the experiments can be conducted at elevated pressures and with liquid electrolyte present. We will firstly present our contributions to characterizing Li-ion battery electrodes [1] and electrolytes [2] using APPES as a precondition to achieve reliable in-situ and operando studies on working batteries.

Secondly, we present our work on electrode/electrolyte interfaces to investigate changes in Galvani potential using operando APPES [3]. For Li-ion batteries, Galvani potential differences (i.e. the electrostatic potential difference between two phases in contact) play an important role for the reaction kinetics at the functional electrode/electrolyte interphases. However, due to lack of suitable measurement techniques, so far little is known about how the Galvani potential difference behaves during Li-ion battery operation. We will show our approach on measuring how a change in Galvani potential difference can be followed as a function of applied external voltage using operando APPES, even without direct access to the electrode/electrolyte interface.

[1] J. Maibach, C. Xu, S. K. Eriksson, J. Åhlund, T. Gustafsson, H. Siegbahn. H. Rensmo, K. Edström, M. Hahlin, Rev. Sci. Inst. 86 (2015), 044101.

[2] J. Maibach, I. Källquist, M. Andersson, S. Urpelainen, K. Edström, H. Rensmo, H. Siegbahn, M. Hahlin, Nature Comm. 10 (2019), 3080.

[3] F. Lindgren, I. Källquist, M.-T. Lee, A. Shavorskiy, K. Edström, H. Rensmo, L. Nyholm, J. Maibach, M. Hahlin, in preparation.

Many chemical reactions involve the presence of solids, liquids and gases concurrently, for instance, heterogeneous catalysis, materials corrosion and others. Complex phenomena may occur at solid-liquid-gas interfaces. Direct monitoring the interfacial reactions at the nanoscale is significant for understanding the reaction mechanisms and developing strategies to control the reactions. By developing and applying liquid cell transmission electron microscopy (TEM), my group studies the dynamic nanoscale phenomena at solid-liquid-gas interfaces with high spatial and temporal resolution. In this talk, I will first show the observed accelerated etching of Au nanostructures with the presence of gas nanobubbles. Through tracking the evolution of local reaction profile and theoretical modeling, an understanding of the triple phase reactions and gas diffusion pathways at the interfaces is developed. I will also show that the solid-liquid-gas interfaces can play a critical role in mediating the oxidative etching by allowing the reduction reactions in a near distance. Future work on in situ TEM studies of the solid-liquid-gas interfaces and device applications will also be discussed.