Hollow cobalt-nickel phosphide nanocages for efficient electrochemical overall water splitting
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Published online 30 September 2020 | https://doi.org/10.1007/s40843-020-1475-2
Hollow cobalt-nickel phosphide nanocages for efficient electrochemical overall water splitting 1,2
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Zhiyuan Wang , Jia Yang , Wenyu Wang , Fangyao Zhou , Huang Zhou , Zhenggang Xue , 2 1* 2* Can Xiong , Zhen-Qiang Yu and Yuen Wu ABSTRACT A low-cost, highly efficient and strong durable bifunctional electrocatalyst is crucial for electrochemical overall water splitting. In this paper, a self-templated strategy combined with in-situ phosphorization is applied to construct hollow structured bimetallic cobalt-nickel phosphide (CoNiPx) nanocages. Owing to their unique hollow structure and bimetallic synergistic effects, the as-synthesized CoNiPx hollow nanocages exhibit a high electrocatalytic activity and stability towards hydrogen evolution reaction in all-pH electrolyte and a remarkable electrochemical performance for −1 oxygen evolution reaction in 1.0 mol L KOH. Meanwhile, with the bifunctional electrocatalyst in both anode and cathode for overall water splitting, a low voltage of 1.61 V and superior stability are achieved at a current density of −2 20 mA cm . Keywords: bimetallic cobalt-nickel phosphide, hollow nanocage, electrochemical water splitting, all-pH electrolyte
INTRODUCTION The increasing energy consumption and serious environmental problems have forced us to develop sustainable and environment-friendly energy systems [1,2]. Among numerous renewable energies, hydrogen (H2) is regarded as one of the promising energy carriers to replace fossil fuels, owing to the high energy efficiency and non-polluting product [3,4]. In recent decades, the fast development and wide application of H2 fuel cells have led to a huge demand for H2 preparation. Electrochemical water splitting, a clean and efficient technology, is considered as one of the most promising approaches to obtain H2 with high purity. However, because of the sluggish reaction kinetics and non-negligible overpotential (η) for both hydrogen evolution reaction (HER) and oxygen
evolution reaction (OER) during water electrolysis [5–8], the large-scale H2 preparation is seriously restricted, which has driven the exploration of high-efficiency electrocatalysts. Nowdays, the most widely used electrocatalysts for HER and OER are noble metals and their oxides, such as platium (Pt) [9,10], iridium (Ir) [11,12], iridium dioxide (IrO2) [13,14] and ruthenium (Ru) [15– 17]. Unfortunately, the scarcity and high-costs hinder their industrial applications. Therefore, to develop bifunctional electrocatalysts with low-cost but high activity and stability towards both OER and HER is extremely urgent [18–20]. In recent years, transition-metal oxides and corresponding transition metal phosphides [21–24], sulfides [25,26], nitrides [27,28], and selenides [29–31] have been extensively studied as non-precious bi-functional electrocatalysts for overall water-splitting. In particular, transition metal phosphides, especially bimetallic transition metal phosphides have attracted signifi
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