Non-metallic electronic regulation in CuCo oxy-/thio-spinel as advanced oxygen evolution electrocatalysts

Abstract

Developing cost-effective and high-performance oxygen evolution reaction (OER) electrocatalysts has become the intense research on pursuing emerging renewable energy conversion, in which exploring and investigating the intrinsic nature of efficient and stable CuCo spinel catalysts toward OER in alkaline media is highly desirable. Herein, Cu1– x Co2+ x O4 oxy-spinel nanoflakes are fabricated by a facile hydrothermal method with the oxidation of ammonia water. In the same condition, Cu1– x -Co2+ x S4 thio-spinel nanospheres are formed without oxidation. In OER process, the as-obtained Cu1– x Co2+ x O4 nanoflakes and Cu1– x Co2+ x S4 nanospheres possess the anodic overpotential of 267 and 297 mV in alkaline media to drive the current density of 10 mA/cm2, respectively, outperforming the state-of-the-art noble metal catalyst of RuO2. X-ray photoelectron spectroscopy analysis exhibits the higher ratio value of Co(III)/Co(II) in Cu1– x Co2+ x O4 than that in Cu1– x Co2+ x S4, suggesting that the strongly-electronegative oxygen efficiently predominates in regulating valence states of Co active sites in spinel structures. Remarkably, density functional theory simulation further reveals that the increased valence state of Co could accelerate the electron exchange between catalysts and oxygen adsorbates during electrocatalysis, thus contributing to the higher OER activity of Cu1– x Co2+ x O4 catalysts. This work provides deep insight regarding the significance of non-metal element (O and S) in CuCo spinel structure catalysts, as well as presents a promising approach to exploit higher performance and grasp the mechanism of various non-noble-metal spinel catalysts for water oxidation.