Preparation and characterization of mono-substituted Wells-Dawson polytungstates have further extended an increasing library of functionalised polyoxometalates, shown in Table . McCormac and co-workers reported a comparative electrochemical study for a series of substituted Wells-Dawson polytungstates, [M(H2O)P2W17O61] q-(M = Fe(III), Cu(II), Co(II), Ni(II), Mn(III) and Mn(II). Cyclic voltammetry experiments confirmed the presence of three, two-electron reduction waves corresponding to the oxo-tungsten sites. The peripheral cation can be formally reduced and re-oxidized without any degradation to the structural integrity of the polytungstate. Motivated by their previous work, Ni(II), Cu(II) and Fe(III)-substituted Wells-Dawson polytungstates were applied to the electroreduction of nitrite using aqueous [M(H2O)P2W17O61] q-anions as the base of catalysis. Initially, the parent anion was previously seen to catalyse electroreduction of the substrate at pH equal to 2.00, via redox mediation but at pH equal to 4.50 no electrocatalysis was observed. At the latter pH value, Cu(II) and Fe(III)-substituted Wells-Dawson polytungstates were revealed as the most efficient electrocatalysts. Preparation of noble metal(III)-substituted Dawson polyoxotungstates, [M(H2O)P2W17O61] q-(Rh(III), Ir(III)) have been reported and characterised accordingly. Table . Reported structures for the mono-substituted Keggin, [M(ligand)PW11O39] q-, and Wells-Dawson, [M(ligand)P2W17O61] q-, anions. Note that axial ligands for such derivatives can be extensive and for this reason have been restricted for the purpose of this paper.