NiCo₂Se₄Nanowires as a High-Performance Bifunctional Oxygen Electrocatalyst

Abstract

Rechargeable zinc–air batteries are attracting great attention due to their high theoretical specific energy, safety, and economic viability. However, their performance and large-scale practical applications are largely limited by poor durability and high overpotential on the air-cathode due to the slow kinetics of the oxygen evolution and reduction reactions (OER/ORR). Therefore, it is highly desired to develop new bifunctional catalysts to improve the OER and ORR kinetics. In this paper, NiCo2Se4 nanowires were uniformly grown on carbon fiber paper (CFP) for the first time. With an overpotential for OER of 327 mV, NiCo2Se4 nanowires show a better performance than RuO2 (350 mV) and a high stability. Moreover, their half-wave potential of 0.77 V and limiting current density of 3.75 mA·cm−2 make it a promising non-precious-metal catalyst for ORR, with performance close to Pt/C (0.87 V, 3.7 mA·cm−2). The excellent performance is attributed to the nanowire morphology with efficient 1D electronic pathways, high conductivity of NiCo2Se4 and an enhanced electronic structure, thanks to a mixed valence of nickel and cobalt ions.

Design Principle of Monoclinic NiCo2Se4 and Co3Se4 Nanoparticles with Opposing Intrinsic and Geometric Electrocatalytic Activity toward the OER

“…Therefore, in cases of only Co, the coexistence of Co­(II) and Co­(III) forces the system to adopt the Co 3 Se 4 phase. − In bimetallic Ni,Co-based compounds, particularly when Co is used in excess, both metal ions can adopt multivalency: i.e., both Ni and Co exist in II and III oxidation states. Such an observation was reported earlier for NiCo 2 Se 4 by Sancho et al and Cabot et al , Interestingly, this phenomenon has also been reported for bimetallic oxides as well. , As Ni is adjacent to Co in the periodic table, they have nearly identical ionic radii in the II and III oxidation states and, as a result, Ni ions can easily replace Co ions in the Co 3 Se 4 phase to produce NiCo 2 Se 4 . A similar phenomenon has been observed by Xia et al for Ni–Co sulfide based materials, where they observed that, while at a lower Ni:Co ratio the formation of Co 3 S 4 or Ni­(II)-substituted Co 3 S 4 is favorable, the formation of NiS as a side product takes place with an increase in the Ni amount …”

“…However, for Ni-rich systems, some amount of NaOH reacted with Ni to form Ni 3 (NO 3 ) 2 (OH) 4 and was thus unavailable to take part in the reaction with Se that was found to be present before addition of NaOH. This leads to the presence of both Ni 3 (NO 3 ) 2 (OH) 4 40,41 Interestingly, this phenomenon has also been reported for bimetallic oxides as well. 42,43 As Ni is adjacent to Co in the periodic table, they have nearly identical ionic radii in the II and III oxidation states and, as a result, Ni ions can easily replace Co ions in the 44 Morphology Evaluation.…”

Iron-Based Electrocatalysts for Energy Conversion: Effect of Ball Milling on Oxygen Reduction Activity

“…where Cs is the specific capacitance (Fg −1 ), A is the integrated area of the CVs, m is mass of electrocatalyst at the electrode surface (g), k is potential scan rate (mVs −1 ) and ∆V is the potential window. The electrochemical surface area (ECSA) was obtained by Equation (3) [50][51][52]:…”

In situ growth of SeOx films on the surface of Ni–Fe–selenide nanosheets as highly active and stable electrocatalysts for the oxygen evolution reaction

“…[2][3][4][5] Although noble metal-based Ir or RuO 2 catalysts can significantly reduce the overpotential and accelerate the kinetics of OER, however, the high cost impedes their extensive applications. [6][7][8][9][10] Thus, over the past few years, many earth-abundant materials with lower cost have been developed to improve the reaction efficiency of OER, such as the transition metal-based selenides, 11,12 nitrides, [13][14][15] sulfides, 16,17 phosphides 18,19 and oxides, [20][21][22] etc., supported non-metallic carbon compounds electrocatalysts. 23,24 Among them, transition metal-based selenides have been reported as prospective OER catalysts due to their intrinsically metallic conductive property which would efficiently enhance the electron transfer capability during catalytic reaction process.…”