Nitrogen doped MoS2 nanosheets synthesized via a low-temperature process as electrocatalysts with enhanced activity for hydrogen evolution reaction
Graphical abstract
Introduction
Hydrogen (H2), as a clean and promising energy, has received tremendous interest due to the increasing environmental concerns and consumption of fossil fuels [1], [2], [3], [4]. The hydrogen evolution reaction (HER) from water splitting has been widely regarded as a sustainable clean pathway for hydrogen production [5], [6], [7], [8]. During HER process, the catalyst plays an essential role in reducing overpotential, promoting the reaction kinetics and thus enhancing the HER catalytic efficiency. Pt-based catalysts have been so far the most efficient catalysts for HER, but their high cost and scarcity have hampered its widespread applications [9], [10], [11], [12], [13]. Therefore, it remains a hugely challenge to develop the inexpensive and earth-abundant catalyst within good catalytic property and high cycling stability.
Recently, transition metal sulfides (MoS2, WS2 et al.) [13], [14], [15], [16], [17], [18] have been intensively investigated as HER catalysts. Theoretical and experimental studies have indicated that Mo and S edges of MoS2 are catalytically active sites for HER [19], [20], [21]. To improve the HER catalytic activity of MoS2, some general strategies have been attempted [22], [23], [24], [25], [26], [27], [28], including the controlled particle size/morphology, improved electrical conductivity, composite effect and element doping, etc. Note that element doping is one of the effective methods to rationally optimize HER activity of MoS2 by changing the atomic arrangement and electron density state [29], [30], [31]. It has been reported that metal (such as Co, Ni, Fe and Cu) [30], [31] or non-metal (N, P, O, Se, Cl et al.) [32], [33], [34], [35] atoms were doped to replace Mo or S atoms, respectively, which modified their electronic properties and boost intrinsic conductivity. Sun et al. [32] have developed a flower-like N-doped WS2 which were synthesized by the sol–gel process and subsequent annealing treatment. N-doping could introduce more charge carriers and improve the intrinsic conductivity and thus revealed the enhanced electrochemical HER activity. Nevertheless, to the best of our knowledge, majority of N atoms doping required complicated and multi-step process, such as high-temperature calcination [36] or harsh requirement (N2 plasma) [37], [38]. Therefore, it would be worthwhile to design a relatively simple, low-temperature and efficient approach for the preparation of N atoms doped MoS2 to obtain enhanced HER performance.
Here, we developed a nitrogen doped MoS2 (N-doped MoS2) as an efficient catalyst for HER by simple hydrothermal reaction. By incorporation of nitrogen atom (replace S atom), more active edge sites were exposed and thus enhanced catalytic performance of MoS2. The theoretical calculations confirmed that the active sites in N-doped MoS2 were S atoms tuned by N doping and Mo atoms tuned by S defects. As expected, the obtained N-doped MoS2 presented an enhanced HER catalytic activity with low overpotential of -168 mV (-10 mA cm-2), small Tafel plot of 40.5 dec mV-1 and superior long-term stability.
Section snippets
Experimental section
Chemicals: ammonium tetrathiomolybdate ((NH4)2MoS4), dicyandiamide (C2H4N4) and iso-Propyl alcohol (C3H8O) were purchased from Sinopharm Chemical Reagents Beijing Co. All of the reagents were of analytical grade and used without further treatment. Deionized (D.I.) water was purified using a Milli-Q system (Millipore, Billerica, USA).
Results and discussion
The N-doped MoS2 and MoS2 were synthesized by simple hydrothermal reaction at reactively low temperature. The crystalline nature of obtained materials was investigated by powder X-ray diffraction (XRD). As shown in Fig. 1a, the obtained MoS2 showed four peaks at 14.1°, 33.4° 40.0° and 58.9°, corresponding to the (002), (100) (103) and (110) lattice plane, agreeing well with the standard pattern of hexagonal MoS2 (JCPDS card No. 73-1508) [16]. Nevertheless, after doping nitrogen, the (002) peak
Conclusion
In summary, we have developed an effective and low-temperature synthesis method to prepare the N-doped MoS2 as efficient electrocatalysts for HER. By introducing nitrogen atoms, 1) the N-doped MoS2 revealed more homogeneous than pure MoS2, resulting in the higher electrochemical active area; 2) more Mo active sites were exposed by abundant defects and the ΔGH* of S atoms were simultaneously tuned by doped N atoms. Thus, compared with pure MoS2, the N-doped MoS2 become more active for HER and
Acknowledgment
This work was supported by Project of Public Interest Research and Capacity Building of Guangdong Province (2014A010106005), Guangdong Innovative and Entrepreneurial Research Team Program (2014ZT05N200) and the National Natural Science Foundation of China (51502096).
References (46)
- et al.
Electrochim. Acta
(2015) - et al.
Nat. Mater.
(2016) - et al.
Nano Energy
(2016) - et al.
Nano Energy
(2016) - et al.
Comput. Mater. Sci.
(1996) - et al.
Energy Environ. Sci.
(2016) - et al.
Energy Environ. Sci.
(2016) - et al.
J. Mater. Chem. A
(2015) - et al.
Nanoscale
(2015) - et al.
Chem. Soc. Rev.
(2015)
Nanoscale
Chem. Sci.
Adv. Mater.
Angew. Chem. Int. Ed.
J. Mater. Chem. A
Small
J. Mater. Chem. A
Adv. Energy Mater.
Acs Appl. Mater. Inter.
Adv. Mater.
Adv. Funct. Mater.
J. Mater. Chem. A
Adv. Funct. Mater.
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These authors contributed equally to the work.