Hierarchical ultrathin carbon encapsulating transition metal doped MoP electrocatalysts for efficient and pH-universal hydrogen evolution reaction

• Published in: Nano energy Vol. 70; p. 104445
• Main Authors: Xiao, Weiping, Zhang, Lin, Bukhvalov, Danil, Chen, Zupeng, Zou, Zhaoyong, Shang, Lu, Yang, Xiaofei, Yan, Daqiang, Han, Fengyan, Zhang, Tierui
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.04.2020
• Subjects: Density functional theory; Electrocatalysis; Hybrid nanostructures; Hydrogen evolution reaction; Transition metal phosphide; Hybrid nanostructures; Electrocatalysis; Hydrogen evolution reaction; Density functional theory; Transition metal phosphide
• ISSN: 2211-2855
• DOI: 10.1016/j.nanoen.2020.104445

Molybdenum phosphide (MoP) has been recognized as a promising family of non-noble metal electrocatalysts for hydrogen evolution reaction (HER) by water splitting, but their electrocatalytic HER activities are still far from desirable and the active sites of MoP-based electrocatalysts have rarely been explored. Herein, we demonstrate a novel hybrid nanostructure composed of carbon encapsulating ultra-low Co/Ni-doped MoP nanoparticles, which can be adopted as highly active and stable HER catalysts in pH-universal electrolytes. The optimized carbon-encapsulated MoP nanoparticles with a Ni/Mo molar ratio of 0.02 achieve a low overpotential of 102 mV at 10 mA cm−2 and a small Tafel slope of 58.1 mV dec−1 in 0.5 M H2SO4 solution, outperforming most of previously reported MoP-based electrocatalysts. More importantly, density functional theory based calculations reveal that the △GH* of Ni/Co doped MoP at the Mo site is lower than that at the P site, and the lowest △GH* of the doping form of Ni and Co at Mo site was interstitial and substitutional + interstitial, respectively. Higher catalytic performance is observed on doped Mo-terminated surface especially in the presence of non-stoichiometric Ni and Co defects. The lowest free energy of Ni-doping implies that Ni-doped MoP hybrid nanostructures possess weak hydrogen adsorption energy and excellent HER catalytic activity in a wide pH range. The combined experimental and theoretical study paves the way for the identification of the active sites in MoP-based hybrid electrocatalysts toward high-performance HER. [Display omitted] •Ultrathin carbon encapsulating Co-/Ni-doped MoP electrocatalysts were fabricated.•HER performance over the hybrid electrocatalyst is significantly improved.•Active sites of doped MoP nanostructures toward pH-universal HER are revealed.•Ultra-low loading and ultrathin carbon shell favour highly efficient and stable HER.