Heterogeneous Electrocatalytic Oxygen Evolution Reaction by a Sol‐Gel Electrode with Entrapped Na₃[Ru₂(μ‐CO₃)₄]: The Effect of NaHCO₃

Abstract

The Na3[Ru2(µ‐CO3)4] complex is acting as a water oxidation catalyst in a homogeneous system. Due to the significance of heterogeneous systems and the effect of bicarbonate on the kinetic, we studied the bicarbonate effect on the heterogeneous electrocatalyst by entrapping the Na3[Ru2(µ‐CO3)4] complex in a sol‐gel matrix. We have developed two types of sol‐gel electrodes, which differ by the precursor, and are demonstrating their stability over a minimum of 200 electrochemical cycles. The pH increases affected the currents and kcat for both types of electrodes, and their hydrophobicity, which was obtained from the precursor type, influenced the electrocatalytic process rate. The results indicate that NaHCO3 has an important role in the catalytic activity of the presented heterogeneous systems; without NaHCO3, the diffusing species is probably OH‐, which undergoes diffusion via the Grotthuss mechanism. To the best of our knowledge, this is the first study to present a simple and fast one‐step entrapment process for the Na3[Ru2(µ‐CO3)4] complex by the sol‐gel method under standard laboratory conditions. The results contribute to optimizing the WSP, ultimately helping expand the usage of hydrogen as a green and more readily available energy source.

Sol–gel-derived nanostructured electrocatalysts for oxygen evolution reaction: a review

“…The sol–gel was processed for two types of electrodes, depending on the precursor. 155 When tested over 200 electrochemical cycles, substantial stability was demonstrated. Also, its electrocatalytic activity was affected by pH, where a higher k cat was achieved with an increase in pH.…”

Unique activity of a Keggin POM for efficient heterogeneous electrocatalytic OER

“… 21 , 22 , 23 , 24 , 25 Hence, by designing a catalyst for OER at low pH, the overall energy requirement for water splitting could be substantially reduced. 26 , 27 …”

“…The sol-gel matrix is common for the entrapment of various active species such as organic and inorganic compounds, nanoparticles of metals and metal oxides, enzymes, and many more active species. 27 , 61 , 62 , 63 , 64 , 65 , 66 Preparing SiO 2 -based matrices using the sol-gel method has gained attention due to the simplicity and versatility of the process. Recent results indicate that the pH affects the k cat of the electrochemical process, and the sol-gel precursors type affect the hydrophobicity of the matrix and influence the electro-catalytic process.…”

“…Recent results indicate that the pH affects the k cat of the electrochemical process, and the sol-gel precursors type affect the hydrophobicity of the matrix and influence the electro-catalytic process. 27 Those features of the sol-gel matrix could improve the OER process; therefore, in the present work, we used the sol-gel process to entrap POM inside a sol-gel matrix and prepare a stable, robust, heterogenized POM for electrocatalytic OER at acidic pH. The sol-gel matrix provides stability and heterogeneity to the POM, allowing the recyclability of the electrode for prolonged use and making it a sustainable and feasible approach.…”