Hydroxylated high-entropy alloy as highly efficient catalyst for electrochemical oxygen evolution reaction
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Published online 10 September 2020 | https://doi.org/10.1007/s40843-020-1461-2
Hydroxylated high-entropy alloy as highly efficient catalyst for electrochemical oxygen evolution reaction 1
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Peiyan Ma , Shichao Zhang , Mutian Zhang , Junfeng Gu , Long Zhang , Yuchen Sun , Wei Ji and 2* Zhengyi Fu Oxygen evolution reaction (OER), a half reaction involved in electrochemical water splitting, CO2 reduction, and metal–air batteries, restricts the efficiency of these energy conversion systems due to sluggish reaction kinetics [1,2]. To accelerate OER, highly efficient electrocatalysts are required. However, large-scale applications of the normally used OER catalysts (i.e. RuO2 and IrO2) are hampered by their instability and low abundance. It is highly desirable to develop earth-abundant catalysts with low cost, high activity and long-term stability. Co(Ni,Fe) (oxy)hydroxides (Co(Ni)-(O)OH) have emerged as promising OER catalysts in recent years [3]. The catalytic activities of ternary (oxy)hydroxides exceed those of single or binary (oxy)hydroxides due to the charge redistribution and optimized absorbing ability to *OH [4,5]. In-situ preparation of multi metals-based (oxy)hydroxides on metals or alloys can afford fast electron transfer, benefit the exposure of catalytic sites and keep the morphological stability in the electrochemical test. High-entropy alloys (HEAs) possess uniform element distribution and favourable conductivity [6]. Most HEAs contain Co, Fe and Ni metals. Particularly, the addition of corrosion-resistant metals (i.e. Cr and Al) endows HEAs with superior anti-corrosion properties in basic electrolyte. Dai et al. [7] optimized the performance of MnFeCoNi HEA catalyst for OER by constructing metal oxide nanosheets on HEA. Their study shows the interface regulation is an effective strategy to promote the catalytic activity of HEA. In this study, a highly efficient electrocatalyst for OER − was fabricated by introducing abundant OH groups on the CoCrFeNiAl HEA precursor. The Co,Fe,Ni-(O)OH sheets were generated after HF treatment and subsequent 1 2
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electrochemical activation. The as-obtained HEAsupported Co,Fe,Ni-(O)OH electrocatalyst exhibits an exceptional performance for OER. Fig. 1a shows the granular morphology of HEA with −1 micron size. The HEA treated by 0.4 mol L HF (HFHEA) presents hierarchical platelets, in good agreement with the morphology of the two-dimensional (2D) metal (oxy)hydrooxides (Fig. 1b). The transmission electron microscopy (TEM) image confirms the formation of heterostructure after HF treatment, which consists of HEA core and metal (oxy)hydrooxide shell (Fig. 1c) with a thickness of about 150 nm. From the energy dispersive spectrometer (EDS) mappings, the distribution of Co, Cr, Fe, Ni, Al and O is quite uniform (Fig. 1d and e1–e6). The selected area electron diffraction (SAED) pattern shows a typical ring structure characteristic for polycrystalline materials and agrees well with the Co,NiOOH and Co(OH)2 (Fig. S1). In the Fourier transform infrared (FTIR) s
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