Research Article: Hollow TiO2@Co9S8 Core–Branch Arrays as Bifunctional Electrocatalysts for Efficient Oxygen/Hydrogen Production

Date Published: December 19, 2017

Publisher: John Wiley and Sons Inc.

Author(s): Shengjue Deng, Yu Zhong, Yinxiang Zeng, Yadong Wang, Xiuli Wang, Xihong Lu, Xinhui Xia, Jiangping Tu.

http://doi.org/10.1002/advs.201700772

Abstract

Designing ever more efficient and cost‐effective bifunctional electrocatalysts for oxygen/hydrogen evolution reactions (OER/HER) is greatly vital and challenging. Here, a new type of binder‐free hollow TiO2@Co9S8 core–branch arrays is developed as highly active OER and HER electrocatalysts for stable overall water splitting. Hollow core–branch arrays of TiO2@Co9S8 are readily realized by the rational combination of crosslinked Co9S8 nanoflakes on TiO2 core via a facile and powerful sulfurization strategy. Arising from larger active surface area, richer/shorter transfer channels for ions/electrons, and reinforced structural stability, the as‐obtained TiO2@Co9S8 core–branch arrays show noticeable exceptional electrocatalytic performance, with low overpotentials of 240 and 139 mV at 10 mA cm−2 as well as low Tafel slopes of 55 and 65 mV Dec−1 for OER and HER in alkaline medium, respectively. Impressively, the electrolysis cell based on the TiO2@Co9S8 arrays as both cathode and anode exhibits a remarkably low water splitting voltage of 1.56 V at 10 mA cm−2 and long‐term durability with no decay after 10 d. The versatile fabrication protocol and smart branch‐core design provide a new way to construct other advanced metal sulfides for energy conversion and storage.

Partial Text

Preparation of TiO2@Co9S8 Core–Branch Arrays: Uniform Co2(OH)2CO3 nanowires arrays were prepared by a simple hydrothermal method. First, 0.75 g Co(NO3)2, 0.25 g NH4F, and 0.75 g CO(NH2)2 were dissolved in 75 mL deionized water to form hydrothermal solution. Then the above solution was transferred into a Teflon‐linked steel autoclave, which was kept at 120 °C for 6 h. After naturally cooling, the Co2(OH)2CO3 nanowires arrays were rinsed by deionized water. Then, the above Co2(OH)2CO3 nanowire arrays were coated with a layer of TiO2 (≈10 nm) by ALD (Beneq TFS 200) with TiCl4 and H2O as the Ti and O precursors at 120 °C for 140 cycles. Then, in a typical sulfurization process, the above TiO2@Co(OH)2CO3 nanowires arrays were immersed into 0.1 m Na2S solution and kept at 90 °C for 9 h. After naturally cooling, the obtained TiO2@Co9S8 core–branch arrays were rinsed by deionized water. For comparison, the Co9S8 nanowires arrays were prepared by a direct sulfurization procedure for Co2(OH)2CO3 nanowires arrays as the same sulfurization parameters above.

The authors declare no conflict of interest.

 

Source:

http://doi.org/10.1002/advs.201700772

 

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