Shanghai Silicate Institute and others have made progress in the design of highly active hydrogen evolution catalysts
Designing low-cost and high-activity hydrogen evolution catalysts for efficient hydrogen production is an important component of establishing a hydrogen energy system. Two-dimensional layered chalcogenide MoS2 has the advantages of simple preparation, stable structure and adjustable catalytic activity, so it is regarded as a very potential acid electrolyzed water hydrogen production catalyst. However, most of its highly active sites are limited to a limited edge. How to realize the activation of MoS2 Basal Plane sites is the key to promote its practical application.
Recently, the computational electrochemistry team led by Liu Jianjun, a researcher at the Shanghai Silicate Research Institute of the Chinese Academy of Sciences, and the nanomaterials research team led by Fan Hongjin, a professor at Singapore's Nanyang Technological University, have made progress in the design of MoS2 in-plane catalytic structures. Theoretical calculation shows that the catalytic adsorption site (S) and the connected transition metals form regional active centers. The concept of regional electronegativity is proposed for the first time to design the catalyst. Different transition metal atoms (V, Cr, Co, Ni) are selected to dope MoS2 surfaces to form different local structures. The charge transfer ability of MoS2 base surface is regulated by different TM-S chemical bond characteristics to optimize the catalytic activity for hydrogen evolution. Based on theoretical calculation, experimental synthesis and electrochemical characterization, it is found that the triangular cobalt doped MoS2 with central sulfur vacancy has excellent hydrogen evolution catalytic performance, with an overpotential of only 75 mV and a Tafel slope of 57 mV dec-1 at a current density of 10 mA cm-2. It is one of the reported materials with excellent hydrogen evolution catalytic performance for two-dimensional MoS2 electrolysis of water. The research results were published in Nature Communications and received positive comments from reviewers.
In addition, the Liu Jianjun team systematically studied the regulation of electronic states and electrocatalytic activity of anions and cations by four classical doping defects of MoS2 and different transition metal elements with boundary structures (transition metal atoms replacing Mo, S-vacancies, Mo-edges and S edges). Regional electronegativity () is proposed as a descriptor of catalytic activity, and the quantitative relationship between coordination environment, doped atom electronegativity, atom radius and valence electron number and regional electronegativity is established, which provides theoretical basis for high activity screening. Relevant results are published in Chemistry of Materials.
The above research work is supported by the National Natural Science Foundation, the Youth Foundation and the Shanghai Municipal Science and Technology Commission's International Cooperation Project.
DFT calculation predicts the effect of local structure doping on HER activity of MoS2. (a) that local configuration of 3CoMo-Vs, 3FeMo-Vs, 1VMo and 1CrMo and (b) the Gibbs free energy diagram of hydrogen evolution for the corresponding configuration. (c) The correlation between the change of Bud charge of the local configuration and the free energy of hydrogen evolution before and after hydrogen evolution around sulfur atoms. In 3CoMo-Vs doped MoS2 structure, the Bud charge changes of (d) Co atom, (e) nearest neighbor S atom and (f) next nearest neighbor Mo atom before and after hydrogen evolution are observed.
A single-layer image diagram of MoS2 doped with different transition metal atoms to form a local structure. AFM images of (a) 3CoMo-Vs, (b) 3FeMo-Vs, (c) 1VMo and (d) 1CrMo samples. (e-h) atomic resolution STEM images of MoS2 samples containing TM and corresponding electron energy loss spectra. These images confirm that Co and Fe atoms tend to form triangular clusters, in which three TM atoms connect to a central sulfur vacancy (3TMMo-Vs, highlighted by a green circle), but V and Cr only form substituted monoatoms without sulfur vacancy (1TMMo, highlighted by a white dotted circle), which is consistent with the theoretical prediction stability. Characterization of HER Catalytic Activity of MoS2 with Different Local Structures. (i) that polarization curve of undoped MoS2, MoS2 have 3CoMo-Vs, 3FeMo-Vs, 1VMo, 1CrMo configurations and Pt/C. (j) Tafel diagram of cathode scan of polarization curve. (k) Compared with the 10-Tafel slope of HER catalyst in 0.5 M H2SO4, MoS2 with 3CoMo-Vs local structure has the highest HER activity.
The correlation between local electronegativity and hydrogen evolution free energy DGH* in MoS2 system with different defect structures doped with transition metal elements.
Study on the Correlation between Experimental Numerical Value and Theoretical Calculation of Local Electronegativity. (a) The correlation between theoretical calculation overpotential and hydrogen evolution free energy of TM doped MoS2 with different defect structures. (b) The theoretical overpotential and the corresponding experimental overpotential and the calculated overpotential. (c) The projected electron density of states of Y @ substitute-Mo. (d) that correlation between local electronegativity and the number of active electrons and the free energy of hydrogen evolution.