4 Search Results

For a high-performance proton exchange membrane water electrolyzer (PEMWE), acidic oxygen evolution reaction (OER) electrocatalysts require highly dispersed iridium oxide (IrO_x) nanoparticles. Although carbon-based materials have been explored as promising supports for IrO_x nanoparticles, their limited stability under harsh oxidative and acidic PEMWE conditions remains a significant challenge. Here, in this study, we report the synthesis and in situ characterization of active and durable IrOx electrocatalysts supported on electrochemically stable and electrically conducting tantalum carbide (TaC). When applied in a PEMWE, the IrO_x/TaC electrocatalyst achieves a cell voltage of 1.71 V at 1.0 A cm^–2, outperforming the commercial IrO₂ catalystmore » (1.82 V at 1.0 A cm^–2). Furthermore, the IrO_x/TaC catalyst maintains a stable operation for 200 h at 0.5 A cm^–2 with a low degradation rate of 36 μV h^–1. Density functional theory calculations further confirm that Ir–O–Ta bond formation at the IrO_x/TaC interface reduces the overpotential of the OER compared to IrO₂. This study underscores the pivotal role of supporting IrO_x over stable and conducting metal carbides, providing guidance for the design of advanced acidic OER catalysts.« less

Electron beam-induced current (EBIC) imaging is a well-established scanning electron microscope (SEM) technique used to analyze the behavior of microelectronic devices including solar cells. Recently, the application of EBIC imaging in an aberration-corrected scanning transmission electron microscope (STEM) has been demonstrated and offers great potential for the in situ study of electronic materials, correlating charge transport properties to atomic structural and elemental information. Here, this work presents two ways to implement EBIC imaging in conventional SEM and STEM systems: one relying on the instrument's inherent scanning and imaging electronics and the other involving third-party systems usually available in electron microscopes.more » The implementation of lock-in EBIC in systems equipped with a fast beam blanker is also described. In addition, this work shows and discusses the different mechanisms at play in EBIC imaging and their dependence on beam energy, sample impedance, and electrical measurement configuration, providing researchers with the basic information needed to apply the technique to their research.« less

The electrochemical carbon dioxide reduction reaction (CO₂RR) using renewable energy sources is a promising solution for mitigating CO₂ emissions. In particular, CO₂RR to formate represents a commercially profitable target. However, a comprehensive understanding of the catalytic mechanisms of Sn-based catalysts under reaction conditions, including the real-time structural evolution of catalysts and the role of all key reaction intermediates in influencing the CO₂RR selectivity, is still lacking. The current study reports a framework to study the selectivity preference of Sn-based bimetallic catalysts using a combination of electrochemical measurements, in situ characterization, and density functional theory (DFT) calculations. The addition of amore » second metal (Co, Ni, Ag, Zn, Ga, Bi) was found to play a vital role in affecting the CO₂RR performance. In situ X-ray absorption near edge structure (XANES) measurements revealed a dynamic evolution in the Sn valence state induced by different secondary metals. A multidimensional descriptor involving all the key reaction intermediates was developed to assess formate selectivity using a 2-dimensional volcano plot. Finally, this research offers an effective framework for understanding CO₂RR catalytic selectivity by considering both the real-time structural evolution of catalysts and all the key intermediates involved.« less

The oxide interfaces between materials with different structural symmetries have been actively studied due to their novel physical properties. However, the investigation of intriguing interfacial phenomena caused by the oxygen octahedral tilt (OOT) proximity effect has not been fully exploited, as there is still no clear understanding of what determines the proximity length and what the underlying control mechanism is. Here, we achieved scalability of the OOT proximity effect in SrRuO₃ (SRO) by epitaxial strain near the SRO/SrTiO₃ heterointerface. We demonstrated that the OOT proximity length scale of SRO is extended from 4 unit cells to 14 unit cells bymore » employing advanced scanning transmission electron microscopy. We also suggest that this variation may originate from changes in phonon dispersions due to electron-phonon coupling in SRO. Here, this study will provide in-depth insights into the structural gradients of correlated systems and facilitate potential device applications.« less