Mo₂C Nanoparticles Dispersed on Hierarchical Carbon Microflowers for Efficient Electrocatalytic Hydrogen Evolution

Abstract

The development of nonprecious metal based electrocatalysts for hydrogen evolution reaction (HER) has received increasing attention over recent years. Previous studies have established MoC as a promising candidate. Nevertheless, its preparation requires high reaction temperature, which more than often causes particle sintering and results in low surface areas. In this study, we show supporting MoC nanoparticles on the three-dimensional scaffold as a possible solution to this challenge and develop a facile two-step preparation method for ∼3 nm MoC nanoparticles uniformly dispersed on carbon microflowers (MoC/NCF) via the self-polymerization of dopamine. The resulting hybrid material possesses large surface areas and a fully open and accessible structure with hierarchical order at different levels. MoO was found to play an important role in inducing the formation of this morphology presumably via its strong chelating interaction with the catechol groups of dopamine. Our electrochemical evaluation demonstrates that MoC/NCF exhibits excellent HER electrocatalytic performance with low onset overpotentials, small Tafel slopes, and excellent cycling stability in both acidic and alkaline solutions.

Molybdenum Carbide Nanoparticles Coated into the Graphene Wrapping N‐Doped Porous Carbon Microspheres for Highly Efficient Electrocatalytic Hydrogen Evolution Both in Acidic and Alkaline Media

“…Interestingly, their Tafel slopes are further decreased to 37, 43, 56 mV dec −1 (Figure 5b). This change trend on the performance is consistent with some previous reports 32, 44, 45, 46. As we know, such a low overpotential (66 mV) to drive the 10 mA cm −2 and small Tafel slope means that Mo 2 C/G3‐NCS750 is one of Mo 2 C‐based electrocatalysts reported with best catalytic activity in alkaline electrolyte (Table S1, Supporting Information).…”

“…The deconvolution analysis of the detailed N1s spectrum (Figure 3c) displays the presence of pyridinic N (398.4 eV), graphitic N (401.7 eV), and N—Mo (396.4 eV) 37, 42. Among these type of N‐doping, the pyridinic N is the main nitrogen species in Mo 2 C/G3‐NCS750, which is beneficial to the HER 32, 34, 37, 39. The presence of low level (less than 4%) of N—Mo species further confirms that N is doped into molybdenum carbide, which is in good agreement with the analysis of Mo 3d spectrum.…”

Electrocatalysts for Hydrogen Evolution in Alkaline Electrolytes: Mechanisms, Challenges, and Prospective Solutions

“…In contrast, the 3D self‐supported electrodes can greatly increase the current density by nearly 5–6 times at the same overpotential compared to traditional electrocatalysts coated on 2D substrates by spin‐coating, dip‐coating, or sputtering method 24, 97. The reasons can be concluded as followings: (1) Commonly 3D current collectors like CC, titanium plate, copper and nickel foam, possess excellent conductivity;98 (2) Robust skeleton and large surface increase effectively the contact area of active surfaces to electrolyte 99. (3) In situ growth on 3D current collectors and do not require polymer binders (such as nafion, polytetrafluoroethylene) to combine electrocatalysts and substrates 100.…”

“…However, their carbides, sulfides and phosphides have been explored recently with good activity toward HER in alkaline electrolytes 57, 106, 116, 117, 118, 119, 120. As molybdenum carbides own the electronic structure similar to that of Pt and possess high resistance to corrosion in alkaline medium, it has attracted extensive research attention as efficient HER electrocatalysts,57 even though these catalysts need relatively large overpotential of 190–230 mV to achieve the appropriate current densities 99. In order to enhance the activity of Mo 2 C, its NPs were dispersed on hierarchical carbon microflowers (Mo 2 C/NCF) via a facile two‐step preparation method through the self‐polymerization of dopamine ( Figure 6 a,b) 99.…”

“…As molybdenum carbides own the electronic structure similar to that of Pt and possess high resistance to corrosion in alkaline medium, it has attracted extensive research attention as efficient HER electrocatalysts,57 even though these catalysts need relatively large overpotential of 190–230 mV to achieve the appropriate current densities 99. In order to enhance the activity of Mo 2 C, its NPs were dispersed on hierarchical carbon microflowers (Mo 2 C/NCF) via a facile two‐step preparation method through the self‐polymerization of dopamine ( Figure 6 a,b) 99. In 1 m KOH solution, the HER activity of Mo 2 C/NCF is enhanced and its overpotentials to achieve 1 and 10 mA cm −2 is reduced to 38 and 100 mV, respectively (Figure 6c,d) 99.…”