Halide-Doping Effect of Strontium Cobalt Oxide Electrocatalyst and the Induced Activity for Oxygen Evolution in an Alkaline Solution

Abstract

Perovskites of strontium cobalt oxyhalides having the chemical formulae Sr2CoO4-xHx (H = F, Cl, and Br; x = 0 and 1) were prepared using a solid-phase synthesis approach and comparatively evaluated as electrocatalysts for oxygen evolution in an alkaline solution. The perovskite electrocatalyst crystal phase, surface morphology, and composition were examined by X-ray diffraction, a scanning electron microscope, and energy-dispersive X-ray (EDX) mapping. The electrochemical investigations of the oxyhalides catalysts showed that the doping of F, Cl, or Br into the Sr2CoO4 parent oxide enhances the electrocatalytic activity for the oxygen evolution reaction (OER) with the onset potential as well as the potential required to achieve a current density of 10 mA/cm2 shifting to lower potential values in the order of Sr2CoO4 (1.64, 1.73) > Sr2CoO3Br (1.61, 1.65) > Sr2CoO3Cl (1.53, 1.60) > Sr2CoO3F (1.50, 1.56) V vs. HRE which indicates that Sr2CoO3F is the most active electrode among the studied catalysts under static and steady-state conditions. Moreover, Sr2CoO3F demonstrates long-term stability and remarkably less charge transfer resistance (Rct = 36.8 ohm) than the other oxyhalide counterparts during the OER. The doping of the perovskites with halide ions particularly the fluoride-ion enhances the surface oxygen vacancy density due to electron withdrawal away from the Co-atom which improves the ionic and electronic conductivity as well as the electrochemical activity of the oxygen evolution in alkaline solution.

An efficient and stable iodine-doped nickel hydroxide electrocatalyst for water oxidation: synthesis, electrochemical performance, and stability

“… 46 These features demonstrated the steadiness of the material toward catalytic activity for OER catalysis and confirmed the relatively higher conductivity and superficial charge-transfer process on the exposed surface of the prepared electrode. 54 However, the multistep chronopotentiometry measurements of the nickel hydroxide and I 2 -loaded nickel hydroxide electrocatalyst were not uniform throughout the experiment and the materials failed to attain the required current density. This suggests that the Ni(OH) 2 and I 2 -loaded Ni(OH) 2 electrocatalysts were not consistent during the catalytic process.…”

Recent Advances in Synergistic Modulation of Transition-Metal-Based Electrocatalysts for Water Oxidation: A Mini Review

“…Moreover, the introduction of N atoms also promoted the value of (∆G *OH − ∆G *OOH ) close to the volcano center, which indicated optimized adsorption energy towards oxygen-containing intermediates during the OER process (Figure 4c,d). Additionally, halogen atoms (F, Cl, and Br) have been proven to effectively modulate the electronic structure of the matrix to improve OER performance [91][92][93][94][95].…”

Material Dynamics of Manganese-Based Oxychlorides for Oxygen Evolution Reaction in Acid

“…By exchanging anions with electronegativities and charges different from those of O 2– , such as halide ions, the electronic structure of catalysts can be modified. For example, the presence of highly electronegative fluorine has been found to create electron-deficient active sites, enhancing electronic conductivity (i.e., amorphous NiFe 2 F 4.4 O 1.8 ) or promoting surface oxygen vacancies (i.e., Sr 2 CoO 3 F), which in turn improve OER performance. Density functional theory calculations have revealed that the incorporation of chlorine, which lies at a lower orbital energy, can upshift the O p-band center and enhance the activity of cobalt-based perovskite oxychlorides (Sr 2 CoO 3 Cl, Sr 3 Co 2 O 5 Cl 2 ).…”