Theoretical Expectation and Experimental Implementation of In Situ Al-Doped CoS2 Nanowires on Dealloying-Derived Nanoporous Intermetallic Substrate as an Efficient Electrocatalyst for Boosting Hydrogen Production

• Published in: ACS catalysis 2019-02, Vol.9 (2), p.1489-1502
• Main Authors: Wang, Mei, Zhang, Wenjuan, Zhang, Fangfang, Zhang, Zhonghua, Tang, Bin, Li, Jinping, Wang, Xiaoguang
• Format: Article
• Language: eng ; jpn
• ISSN: 2155-5435; 2155-5435
• DOI: 10.1021/acscatal.8b04502

Foreign atom doping is known to not only modify the electronic structure but also improve the intrinsic activity of catalysts. Herein, we fabricate three-dimensional (3D) self-supporting nanoporous cobalt–aluminum intermetallic (np-Co­(Al)) through dealloying of Al90Co10 master alloy to in situ introduce Al element into the precursor. The intrinsic Al dopant is determined to be insensitive to S vapor but beneficial to generate numerous Al-doped CoS2 nanowires (Al-CoS2 NWs) when they were subjected to solid–vapor sulfurization treatment. The density functional theory (DFT) calculations evidence that spontaneous Al-doping in CoS2 crystal could enhance the hybridization between Co d-orbital and S p-orbital near the Fermi level. On the one hand, the Co-sites are more active than that of the S-sites, and the intermediate hydrogen (H*) adsorption free energy (ΔG H*) of Al-CoS2 is only −0.16 eV when adsorbed on the bridge site of Co. On the other hand, the embedded Al can not only facilitate the activity improvement of Co-sites but also greatly activate the inert S-sites in CoS2. An overpotential as small as 86 and 191 mV to reach 10 and 100 mA cm–2 H2-evolving current, a small Tafel slope of 62.47 mV dec–1, and long-term operational stability are achieved on the Al-doped CoS2 catalyst. This finding opens up an easily accessible in situ doping route via alloying-dealloying followed by inheritance to nanoporous earth-abundant chalcogenide electrocatalyst for regulating their physicochemical and electrochemical properties, accelerating the development of high performance H2-evolving electrode for electrochemical hydrogen production.