Switchable wetting of oxygen-evolving oxide catalysts

Abstract

The surface wettability of catalysts is typically controlled via surface treatments that promote catalytic performance. Here we report on potential-regulated hydrophobicity/hydrophilicity at cobalt-based oxide interfaces with an alkaline solution. The switchable wetting of single particles, directly related to their activity and stability towards the oxygen evolution reaction, was revealed by electrochemical liquid-phase transmission electron microscopy. Analysis of the movement of the liquid in real time revealed distinctive wettability behaviour associated with specific potential ranges. At low potentials, an overall reduction of the hydrophobicity of the oxides was probed. Upon reversible reconstruction towards the surface oxyhydroxide phase, electrowetting was found to cause a change in the interfacial capacitance. At high potentials, the evolution of molecular oxygen, confirmed by operando electron energy-loss spectroscopy, was accompanied by a globally thinner liquid layer. This work directly links the physical wetting with the chemical oxygen evolution reaction of single particles, providing fundamental insights into solid–liquid interfacial interactions of oxygen-evolving oxides.

Electrochemical Urea Oxidation in Different Environment: From Mechanism to Devices

“…[60] Moreover, hydrophilicity of the catalyst surfaces could promote the charge-transfer rate between the electrolyte and electrode to effectively boost the proton coupled electron transfer (PCET) process without transfer decaying caused by the coverage of gas produced. [61] The hydrophobicity of the anodic oxides could be reduced due to electrowetting and OH À accumulation at the electrode surfaces, [62] more OH À attached beneficial of improved UOR performance. It is worth noting that several regulation strategies are always employed at the same time to promote the UOR performance, meaning sometimes one-factor change usually accompanies with others.…”

Carbothermal Shock Synthesis of High Entropy Oxide Catalysts: Dynamic Structural and Chemical Reconstruction Boosting the Catalytic Activity and Stability toward Oxygen Evolution Reaction

“…The samples after synthesis maintained a spinel oxide crystal structure, commonly observed in literature for Fe/Ni/Co alloys. [ 40–47 ] Recent results presented in literature, and by this group, utilizing CTS to synthesize nanoparticles showed formation of HEA when noble metals (e.g., Pt, Pd, and Au) were present in the HEA composition. [ 31 ] On the other hand, our presented study, herein, for exclusively non‐noble metals chemistry (Fe, Ni, Co, Cr, Mn, and V) showed the formation of an oxide phase (i.e., high entropy oxide (HEO)), instead of metallic HEA.…”

“…This observation is in line with other literature reports, where catalyst morphological perturbations occur at catalyst surfaces during OER (e.g., increased surface roughness and porosity). [40,41,47] In addition, recent literature report showed that surface reconstruction for HEO system can happen under electrochemical activation or during OER. [23,[57][58][59] All our synthesized HEO catalysts, regardless of their alloying order (ternary, quaternary, quinary, or senary), showed a significantly higher OER activity compared to stateof-the-art commercial IrO 2 catalyst.…”

“…Fe-Co spinel compounds, reported in the literature, have shown a tendency toward the formation of oxyhydroxide phase during testing under OER conditions in aqueous alkaline medium. [41,47] Cycling the samples under OER conditions results in increasing the oxidation state of Co species and surface reconstruction was observed, where more porosity evolved. [40,41,47] These observations aligned with our STEM imaging analysis, as shown in Figure 3.…”

“…[41,47] Cycling the samples under OER conditions results in increasing the oxidation state of Co species and surface reconstruction was observed, where more porosity evolved. [40,41,47] These observations aligned with our STEM imaging analysis, as shown in Figure 3. Therefore, XRD measurement was performed to unravel the structural changes that occurred after testing HEO catalyst in OER.…”