Importance and Challenges of Electrochemical in Situ Liquid Cell Electron Microscopy for Energy Conversion Research

Abstract

The foreseeable worldwide energy and environmental challenges demand renewable alternative sources, energy conversion, and storage technologies. Therefore, electrochemical energy conversion devices like fuel cells, electrolyzes, and supercapacitors along with photoelectrochemical devices and batteries have high potential to become increasingly important in the near future. Catalytic performance in electrochemical energy conversion results from the tailored properties of complex nanometer-sized metal and metal oxide particles, as well as support nanostructures. Exposed facets, surface defects, and other structural and compositional features of the catalyst nanoparticles affect the electrocatalytic performance to varying degrees. The characterization of the nanometer-size and atomic regime of electrocatalysts and its evolution over time are therefore paramount for an improved understanding and significant optimization of such important technologies like electrolyzers or fuel cells. Transmission electron microscopy (TEM) and scanning transmission electron microscope (STEM) are to a great extent nondestructive characterization tools that provide structural, morphological, and compositional information with nanoscale or even atomic resolution. Due to recent marked advancement in electron microscopy equipment such as aberration corrections and monochromators, such insightful information is now accessible in many institutions around the world and provides huge benefit to everyone using electron microscopy characterization in general. Classical ex situ TEM characterization of random catalyst locations however suffers from two limitations regarding catalysis. First, the necessary low operation pressures in the range of 10(-6) to 10(-9) mbar for TEM are not in line with typical reaction conditions, especially considering electrocatalytic solid-liquid interfaces, so that the active state cannot be assessed. Second, and somewhat related, is the lack of time resolution for the evaluation of alterations of the usually highly heterogeneous nanomaterials. Two methods offer a solution to these shortcomings, namely, identical location TEM (IL-TEM) and electrochemical in situ liquid TEM. The former is already well established and has delivered novel insights particularly into degradation processes; however, characterization is still performed in vacuum. The latter circumvents this issue by using dedicated in situ TEM holders but introduces extremely demanding technical challenges. Although the introduction of revolutionizing thin SiN window cells, which elegantly confine the specimen from vacuum, has allowed demonstration of the potential of the in situ approach, the reproducibility and data interpretation is still limited predominately due to the strong interaction of the electron beam with the supporting electrolyte and electrode material. Because of the importance of understanding the nanoelectrochemical structure-function relationship, this Account aims to convey a timely perspective on the opportunities and particularly the ch...

Perovskite Electrocatalysts for the Oxygen Reduction Reaction in Alkaline Media

“…Furthermore, surface-enhanced vibrational spectroscopy has also been used to track the formation of surface states with relevance to the ORR [210,211]. Changes in the morphology of a fuel cell material have been resolved by transmission electron microcopy (TEM) using a commercial liquid cell [212] but several challenges need to be overcome to provide the resolution required for catalytic insight [213]. The latter should be supported by rigorous electroanalytical analysis of the measured currents.…”

Review—Promises and Challenges of In Situ Transmission Electron Microscopy Electrochemical Techniques in the Studies of Lithium Ion Batteries

“…7,94 In situ TEM was first reported by Poppa in the 1960s, and has advanced tremendously in the last several decades, given its potential advantage for studying dynamic processes and structural changes in electrode. 95 There are many advantages for executing an experiment in situ.…”

“…[4][5][6] Electrochemical devices such as batteries and electrochemical capacitors to store and restore electrical energy are possible solutions in the near-term because the conversion between electrical and chemical energy shares a common carrier (electrons). 2,[7][8][9] Moreover, compared to traditional batteries, lithium-ion batteries (LIBs) are more compact, portable, and have a high gravimetric capacity and power density, owing to the lighter molecular weight of lithium. 10,11 LIBs are widely used in present-day portable electronic gadgets such as mobile phones, laptops, tablet computers, and video camcorders, and the medical and aerospace industries for storing photovoltaic-generated dc electricity.…”

Insights into electrochemical dealloying of Cu out of Au-doped Pt-alloy nanoparticles at the sub-nano-scale

“…Initial performances of Pt-alloys are already surpassing the US Department of Energy targets [1]. However, their stability is still under debate and is the topic of many current and future studies [13][14][15][16][17][18][19][20]. Three issues are foreseen for Ptalloys: (i) loss of initially superior ORR activity [13], (ii) formation of unstable porous nanoparticles [9,15] and (iii) poisoning of the PEM FC by the leached less noble metal cations [12,[21][22][23].…”