Polythiophene as an efficient mediator to anchor in situ-grown Ni hydroxide cluster for the urea oxidation reaction

Reported are the synthesis, characterization and eletrocatalytic properties of Ni²⁺@PTh@CC composite electrode (PTh: polythiophene; CC: carbon cloth) for the urea oxidation reaction (UOR). PTh was incorporated as a "double-sided tape" mediator to enhance the connection between catalyst and electrode support, and hence greatly improve the catalytic stability. Additionally, this design allowed the adsorbed Ni²⁺ ion to convert to an active phase, namely a Ni(OH)₂-like cluster, during the UOR, with this conversion substantially decreasing the usage of Ni element (i.e. high atomic utilization rate). An in situ FTIR experiment revealed the formation of cyanate anion (OCN^-) during the UOR when using a Ni metal electrode, while no obvious cyanate anion was detected for a Ni²⁺@PTh@CC composite electrode. This difference implied that cyanate anion might be a poisonous intermediate adsorbate. Apparently, PTh mediator can not only function as a binder but also influence the structure of in situ-formed active phase and further alter the mechanism of the reaction in interest.