Sodium-nickel pyrophosphate as a novel oxygen evolution electrocatalyst in alkaline medium

Abstract

The development of robust and low-cost oxygen evolution reaction (OER) electrocatalysts is a challenging issue in electrochemical water-splitting technology. Tailoring the electrocatalysts through nano- and composition engineering is an effective strategy to enhance the intrinsic and extrinsic electrocatalytic activities. In this study, for the first time, sodium-nickel pyrophosphate (Na2NiP2O7) is proposed as a novel OER electrocatalyst in alkaline environment. First, the electrocatalytic performance of micron-sized Na2NiP2O7 (Na2NiP2O7-micron) is evaluated. In addition, nanoscale Na2NiP2O7 (Na2NiP2O7-nano) and Fe-substituted Na2NiP2O7-nano (Na2Ni1-xFexP2O7-nano) are synthesized to improve the electrocatalytic performance of Na2NiP2O7. Although Na2NiP2O7-micron exhibits low electrocatalytic OER activity in alkaline medium, its catalytic activity can be significantly improved through reducing the particle size and substituting Fe in the Ni sites. The synthesized Na2Ni0.75Fe0.25P2O7-nano exhibits optimal catalytic activity with an overpotential of 300 mV at a current density of 10 mA/cm(2) and long-term durability with continuous O-2 generation over 100 hours in alkaline medium.