Abstract
For a systematic materials selection and for design and synthesis of systems for electrochemical energy conversion with specific properties, it is essential to clarify the general relationship between physicochemical properties of the materials and the electrocatalytic performance and stability of the system or device. The design of highly performant and durable 3D electrocatalysts requires an optimized hierarchical morphology and surface structures with high activity. A systematic approach to determine the 3D morphology of hierarchically structured materials with high accuracy is described, based on a multi-scale X-ray tomography study. It is applied to a novel transition-metal-based materials system: MoNi4 electrocatalysts anchored on MoO2 cuboids aligned on Ni foam. The high accuracy of 3D morphological data of the formed micro- and nanostructures is ensured by applying machine learning algorithms for the correction of imaging artefacts of high-resolution X-ray tomography such as beam hardening and for the compensation of experimental inaccuracies such as misalignment and motions of samples and tool components. This novel approach is validated based on the comparison of virtual cross-sections through the MoNi4 electrocatalysts and real FIB cross-sections imaged in the SEM.
Highlights
The development of technologies for the efficient use of renewable energies has become a research priority worldwide
Ni atoms are characterized by a high reactivity (Ni > Co > Fe > Mn), which is governed by the bond strength of OH–M2+δ, with 0 ≤ δ ≤ 1.5, energetics (Ni < Co < Fe < Mn), a trend which is independent of the source of the OH, i.e., either the supporting electrolyte or the water dissociation product [4]
We have demonstrated a systematic approach to determine the 3D morphology of hierarchically structured materials such as electrocatalysts with high accuracy, based on a micro- and nano- X-ray tomography study
Summary
The development of technologies for the efficient use of renewable energies has become a research priority worldwide. A wide range of materials, especially various transition-metal (TM) based materials (e.g., Fe-, Co-, Mo-, Ni-, V-, Cu-based precursors) and metal-free carbon materials, have been regarded as promising economical and efficient replacements to conventional, expensive precious-metal-based materials (e.g., Pt-, Pd-, Ir-, Au-, Ag-, Ru-based precursors). Some of these advanced electrocatalytically active materials outperform conventional precursors, considering properties like electrocatalytic activity and long-term stability. Mo atoms have superior adsorption properties towards hydrogen. Reactivity and hydrogen adsorption are high for MoxNiy-based electrocatalysts [6]
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