Date Published: January 03, 2018
Publisher: John Wiley and Sons Inc.
Author(s): Huifang Wei, Qiaoya Xi, Xi’an Chen, Daying Guo, Feng Ding, Zhi Yang, Shun Wang, Juan Li, Shaoming Huang.
Molybdenum carbide (Mo2C) is recognized as an alternative electrocatalyst to noble metal for the hydrogen evolution reaction (HER). Herein, a facile, low cost, and scalable method is provided for the fabrication of Mo2C‐based eletrocatalyst (Mo2C/G‐NCS) by a spray‐drying, and followed by annealing. As‐prepared Mo2C/G‐NCS electrocatalyst displays that ultrafine Mo2C nanopartilces are uniformly embedded into graphene wrapping N‐doped porous carbon microspheres derived from chitosan. Such designed structure offer several favorable features for hydrogen evolution application: 1) the ultrasmall size of Mo2C affords a large exposed active sites; 2) graphene‐wrapping ensures great electrical conductivity; 3) porous structure increases the electrolyte–electrode contact points and lowers the charge transfer resistance; 4) N‐dopant interacts with H+ better than C atoms and favorably modifies the electronic structures of adjacent Mo and C atoms. As a result, the Mo2C/G‐NCS demonstrates superior HER activity with a very low overpotential of 70 or 66 mV to achieve current density of 10 mA cm−2, small Tafel slope of 39 or 37 mV dec−1, respectively, in acidic and alkaline media, and high stability, indicating that it is a great potential candidate as HER electrocatalyst.
Preparation of the Catalyst: Chitosan (1 g) was first dissolved deionized water (200 mL) containing acetate acid (2 mL). Second, AM (1 g) was dissolved into deionized water (10 mL), and then added into the 60 mL (5.0 mg mL−1) graphene oxide (GO) solution prepared according to the method reported previously by us.47 Subsequently, the above solution was sprayed into the chitosan solution and further stirred 12 h at room temperature to generate a mixture. Then, the powder was collected after spray‐drying the mixture, and further annealed under Ar at 750 °C for 3 h with a temperature ramping rate of 2 °C min−1 to yield the product (Mo2C/G3‐NCS750). Similarly, when the mass of GO is 0, 0.1, 0.5 g, Mo2C/NCS‐750, Mo2C/G1‐NCS750, and Mo2C/G5‐NCS750 can be readily obtained. For comparison, the Mo2C/G3‐NCS samples were carbonized at different carbonization temperatures such as 650, 850 °C, which were denoted as Mo2C/G3‐NCS650, Mo2C/G3‐NCS850, respectively. The Mo2C/NC750 is prepared using a similar procedure to Mo2C/NCS750, except that the solids were collected by centrifugation instead of spray‐drying. The mass ratio of AM and Chitosan is 2:1, 1:1, and 1:2, the corresponding products are denoted as Mo2C/0.5NC750, Mo2C/NC750, and Mo2C/2NC750, respectively.
The authors declare no conflict of interest.