Hollow and Porous Nickel Cobalt Perselenide Nanostructured Microparticles for Enhanced Electrocatalytic Oxygen Evolution

Nickel and cobalt-based chalcogenides are an interesting class of electrochemically active compounds. Herein we report a two-step synthesis of uniform hollow nickel cobalt perselenide nanostructured microparticles with a corrugated surface, randomly spaced pores, and a tunable composition. In the first step, we synthesized Ni–Co acetate hydroxide prism-shaped microparticles, which were subsequently used as templates for the selenization process at temperatures as low as 80 °C. The substitution of acetate and hydroxide anions with selenide anions at a low temperature eventually produced partially amorphous hollow microparticles due to the nanoscale Kirkendall effect. Thin films of the as-synthesized samples behaved as highly active catalysts for the electrochemical oxygen evolution reaction (OER). Among those, Ni 0.88 Co 1.22 Se 4 hollow microparticles showed excellent performances, exhibiting a 10 mA/cm 2 current density at a modest overpotential of 320 mV, a high turnover frequency of 0.146 S 1–, and a long-term operational stability (over 100 h of continuous operation).