Polythiophene as an efficient mediator to anchor <i>in situ</i> -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>i.e.</i> high atomic utilization rate). An <i>in situ</i> 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 <i>in situ</i>-formed active phase and further alter the mechanism of the reaction in interest.