Elsevier

Materials Letters

Volume 264, 1 April 2020, 127307
Materials Letters

A facile method for preparing amorphous Co-Ni-Cu ternary hydroxides as an efficient oxygen evolution reaction electrocatalyst

https://doi.org/10.1016/j.matlet.2020.127307Get rights and content

Highlights

  • Ternary Co-Ni-Cu hydroxides were first used for OER.

  • Co-Ni-Cu hydroxides were prepared via a simple co-precipitation method.

  • CNC835 exhibited excellent OER catalytic performance.

  • Co-Ni-Cu hydroxide has the amorphous thin lamellar structure.

Abstract

High-efficient, low cost and stable electrocatalysts for oxygen evolution reaction (OER) in alkaline solution are very significant for mass production of clean hydrogen fuels. Herein, an amorphous ternary Co-Ni-Cu lamellar hydroxide was synthesized using a facile co-precipitation method. When the molar ratio of Co:Ni:Cu is 8:3:5, the as-prepared hydroxides displayed remarkable activities towards OER in 0.1 M KOH with a low overpotential (337 mV), small Tafel slope (78 mV dec−1) and outstanding stability. These properties are much better than those with different molar ratio. The facile preparation method and excellent electrocatalytic properties endowed this material as a potential candidate for precious metal catalysts for OER.

Introduction

Electrocatalytic water splitting is limited by the bottleneck step of oxygen evolution reaction (OER) due to lack of high-efficient, low cost and stable catalysts. Although precious metal-based electrocatalysts had high catalytic activities, the poor long-term stability and high cost limit their large-scale industrial application [1]. Non-precious transition metal materials, such as sulfides, selenides, phosphides [2], etc., were developed as OER catalysts, however, their long-time catalytic stability were also unsatisfactory, because they would be oxidized to corresponding metal oxides or (oxo)hydroxides during catalytic processes. Therefore, transition metal based oxides and (oxo)hydroxides have been considered as the most promising OER electrocatalysts due to their excellent stability and high efficient [3]. In particular, nickel hydroxide has exhibited good catalytic performance for OER in alkaline media, and the doping with other transition metals like Fe, Cu, Co, etc. to form binary hydroxides or ternary hydroxides could further enhance its intrinsic catalytic activity [4]. Recently, several researches demonstrated that the ternary hydroxides have better catalytic performance than the corresponding binary hydroxides [5]. Furthermore, the charge-transfer effects of Co facilitated the oxidation of insulating Ni(OH)2 to conductive NiOOH [6], Cu could significantly improve the electrical conductivity of amorphous catalyst [7], which inspired us to design and prepare a ternary OER electrocatalyst and nickel hydroxide doped with Co and Cu was envisaged. In addition, amorphous structure was more favorable for OER than the crystalline ones, because it possessed a large number of structure defects and exposed more naked or unsaturated metal active sites, which facilitated the diffusion and reaction of electrolyte ions [8]. Therefore, in this work, we first prepared amorphous Co-Ni-Cu hydroxide via a simple co-precipitation method. The morphology, structure, and surface electronic states of the as-fabricated sample were investigated.

Section snippets

Synthesis of Co-Ni-Cu hydroxides

Typically, 2 mM Co(NO3)2·6H2O, 0.75 mM NiSO4·6H2O, 1.25 mM CuCl2·2H2O, 2 mM citric acid (C6H8O7·H2O) and 0.25 g polyvinyl pyrrolidone were dissolved in 10 mL deionized water under stirring. Then, 1.0 M KOH solution was slowly dropped into above solution under magnetic agitation until the solution pH being 8.5, and the mixture solution turned into grey-blue slurry. After centrifuged rinsed with deionized water and anhydrous ethanol for several times, the sample was dried at 60 ℃ for 12 h, and

Results and discussion

The morphology and structure of the dried CNC835 (actual molar ratio of Co:Ni:Cu is 6.2:3.1:5.0 according to ICPMS) was investigated by SEM (Fig. 1(a) and (b)) and TEM (Fig. 1(c)). Fig. 1(a) revealed that CNC835 was large blocks formed by stacking a large number of lamellared structures, and Fig. 1(b) displayed the lamellared edge was curled and intermediate region was cracked. The TEM test was carried out after the sample proceeding ultrasonic treatment in anhydrous alcohol for 30 min, and the

Conclusions

In summary, novel amorphous ternary Co-Ni-Cu hydroxide was prepared by one-step coprecipitation method, and low overpotential, rapid OER rate, low charge transfer resistance and good catalytic stability of CNC835 was confirmed by LSV, Tafel, EIS and i-t curve in 0.1 M KOH versus Ag/AgCl.

CRediT authorship contribution statement

Hongying Li: Conceptualization, Methodology, Investigation, Data curation, Writing - original draft. Xueliang Wang: Conceptualization, Writing - review & editing. Tao Wang: Visualization, Software, Supervision. Mingcheng Zhao: Investigation, Validation, Resources.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

This work was supported by Natural Science Foundation Committee of Shandong Province, China (Nos. ZR2017MB062 and ZR2015BL014) and the National Natural Science Foundation of China (No. 21105023).

References (13)

There are more references available in the full text version of this article.

Cited by (4)

  • Universal MOF-Mediated synthesis of 2D CoNi-based layered triple hydroxides electrocatalyst for efficient oxygen evolution reaction

    2021, Journal of Colloid and Interface Science
    Citation Excerpt :

    Therefore, the practical application of this type of catalyst is significantly restricted [22,23]. CoNi-based hydroxide is one of the most effective materials for OER, which is deduced to the synergistic enhancement between Co and Ni ions, and the incorporation of a third metal can further enhance its catalytic activity [24-28]. Previous studies have shown that the introduction of Fe into CoNi-based hydroxides to form a layered structure could expose more active sites and promote mass transfer [29].

  • Hollow NiF<inf>2</inf>/CoF<inf>2</inf> cubes as electrode materials for high-performance supercapacitors

    2021, Solid State Sciences
    Citation Excerpt :

    In general, pseudo-capacitors can achieve substantially higher capacitance compared with EDLCs, so tremendous efforts have been devoted to designing active materials with high pseudocapacitive performance, especially transition metal compounds. Many transition metals compounds such as metal oxides/hydroxides [8,9], metal sulfides [10–12], metal phosphides [13,14] have been adequately explored as active materials. Recently, metal fluorides have been paid more attention as a novel kind of active material.

View full text