Resumo

BAYESHOV, Аbduali; BAYESHOVA, Аzhar; ABDUVALIYEVA, Umida  e  BUKETOVA, Aksulu. Mechanisms for Ultrafine Copper Powders Electrolytes Production in the Presence of Titanium Ions. Port. Electrochim. Acta [online]. 2022, vol.40, n.5, pp.373-381.  Epub 31-Ago-2022. ISSN 0872-1904.  https://doi.org/10.4152/pea.2022400505.

Copper (Cu) powder production, in a sulfuric acid (H2SO4) solution with titanium (Ti) ions, was studied by electrolysis, using Cu anodes. It was empirically proven that this process occurs by three different stage-based mechanisms that depend on the electrolyte composition and electrolysis conditions. The first mechanism occurs in a H2SO4 solution with Cu2+ ions and Ti4+ (tetravalent ions). Cu2+ are cathodically reduced, forming Cu powder (CP), since the process occurs at current densities (J) lower than the limiting one. So, part of the current that would be consumed by the hydrogen ions (H+) reduction reaction is spent to reduce Ti4+, which results in Ti3+ (trivalent ions). These, in the cathode space, reduce Cu2+, which, simultaneously, regenerates Ti4+. Then, these diffuse and are again reduced at the cathode, and Ti3+are formed, reducing Cu2+, in a cyclic process that further increases CP production current efficiency (CE) at the near-cathode space, forming more dispersed particles. The second mechanism occurs in a H2SO4 solution with only Ti4+. During the electrochemical circuit current flow, the Cu anode is oxidized to form Cu2+, and Ti4+ are reduced to Ti3+, on the cathode surface. Then, Cu2+ and Ti3+, by diffusing the solution volume and meeting in the inter-electrode space, chemically interact with each other, due to the red-ox (reduction-oxidation) potential difference, forming a dispersed CP and Ti4+. These diffuse one more time, and are again reduced to Ti3+. These processes are cyclically repeated, i.e., Ti4+ work as catalyst. The third mechanism takes place in H2SO4 with Ti3+. When the current flows through the electrolyte, the Cu anode is oxidized, forming Cu2+, which are immediately reduced in the anode by Ti3+, producing CP. Ti4+ are formed due to the red-ox reaction diffusion to the cathode, being reduced to Ti3+on its surface, which again interact with Cu, producing CP on the anode. Since, in all mechanisms (except the first), CP is not directly produced on the cathode surface, but in the inter-electrode space, further growth of Cu particles does not occur. Thus, CP particles of spherical shape, with sizes from 0.01 to 0.1 μm, are formed, with a CE from 95.2 to 99.1%, under optimal conditions.

Palavras-chave : ultrafine CP production mechanisms; H₂SO₄ solution; Ti⁺ electrolytes.

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