Details

Autor(en) / Beteiligte

• Yule, Lewis C.
• Daviddi, Enrico
• West, Geoff
• Bentley, Cameron L.
• Unwin, Patrick R.

Titel

Surface microstructural controls on electrochemical hydrogen absorption at polycrystalline palladium

Ist Teil von

• Journal of electroanalytical chemistry (Lausanne, Switzerland), 2020-09, Vol.872, p.114047, Article 114047

Ort / Verlag

Amsterdam: Elsevier B.V

Erscheinungsjahr

2020

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The ease by which hydrogen is absorbed into a metal can be either advantageous or deleterious, depending on the material and application in question. For instance, in metals such as palladium (Pd), rapid absorption kinetics are seen as a beneficial property for hydrogen purification and storage applications, whereas the contrary is true for structural metals such as steel, which are susceptible to mechanical degradation in a process known as hydrogen embrittlement. It follows that understanding how the microstructure of metals (i.e., grains and grain boundaries) influences adsorption and absorption kinetics would be extremely powerful to rationally design materials (e.g., alloys) with either a high affinity for hydrogen or resistance to hydrogen embrittlement. To this end, scanning electrochemical cell microscopy (SECCM) is deployed herein to study surface structure-dependent electrochemical hydrogen absorption across the surface of flame annealed polycrystalline Pd in aqueous sulfuric acid (considered to be a model system for the study of hydrogen absorption). Correlating spatially-resolved cyclic voltammetric data from SECCM with co-located structural information from electron backscatter diffraction (EBSD) reveals a clear relationship between the crystal orientation and the rate of hydrogen adsorption-absorption. Grains that are closest to the low-index orientations [i.e., the {100}, {101}, and {111} facets, face-centered cubic (fcc) system] facilitate the lowest rates of hydrogen absorption, whereas grains of high-index orientation (e.g., {411}) promote higher rates. Apparently enhanced kinetics are also seen at grain boundaries, which are thought to arise from physical deformation of the Pd surface adjacent to the boundary, resulting from the flame annealing and quenching process. As voltammetric measurements are made across a wide potential range, these studies also reveal palladium oxide formation and stripping to be surface structure-dependent processes, and further highlight the power of combined SECCM-EBSD for structure-activity measurements in electrochemical science.