Development of CuNi immobilized Pt surface to minimize nitrite evolution during electrocatalytic nitrate reduction in neutral medium

Nitrite (NO -2 ) is one of the major troublemakers in our environment, merits rigorous attention on removal purposes via effective treatments. Meanwhile, often NO -2 ions are evolved as stable intermediates during electrocatalytic nitrate reduction reaction (NRR). In the present article, it is shown how the immobilization of Cu and Ni particles on a Pt surface influences both nitrate and nitrite reduction rates in the neutral medium. Using sandwich type membrane reactor, it was observed that NO -3 and NO -2 ions reduced having a first order rate constant (k) of 26.1x10-3 min-1 and 29.5x10-3 min-1, respectively at a Pt-CuNi cathode surface. Due to larger NO -2 reduction rate, NO -2 ions did not appear while NO -3 ions were reduced at the Pt-CuNi electrode surface. At the end of reaction, NH3 was identified as the only product. Beside the evaluation of reactivity and product selectivity, several kinetic properties of NRR at Pt-CuNi surface were also evaluated. A Pt-Cu electrode requires 10.05 kJmol-1 activation free energy, but this energy is decreased to 5.76 kJmol-1 while Pt-CuNi electrode is used to attain NRR in the neutral medium. All the experimental data revealed that incorporation of Ni into Pt-Cu matrix, significantly improves NRR efficiency. In addition, the NRR process does not compete with hydrogen evolution reaction (HER) process at the Pt-CuNi electrode surface. Finally, Pt-CuNi being the efficient catalyst for attaining NRR, this catalyst was characterized with different electrochemical and spectroscopic techniques to unveil inherent physical properties.