Janus (Mo/β-Mo₂C)@C heterostructure as an efficient electrocatalyst for the hydrogen evolution reaction in acidic and alkaline media

Abstract

To explore low-cost, high-efficiency, and noble-metal-free catalysts for electrocatalytic water splitting in both acidic and alkaline media, the metal-metal carbide Janus hierarchical structure comprising Mo and β-Mo2C embedded on a carbon layer (Mo/β-Mo2C)@C is synthesized by a hydrothermal reaction and subsequent low-temperature magnesium thermic process. Systematic characterization by XRD, XPS, Raman scattering, and SEM/TEM reveals the successful formation of metallic Mo and β-Mo2C nanoparticles. The synthesized (Mo/β-Mo2C)@C has a large specific surface area and boasts highly efficient hydrogen evolution reaction activity including low overpotentials of 152 mV and 171 mV at a current density of 10 mA cm-2 and small Tafel slopes of 51.7 and 63.5 mV dec-1 in acidic and alkaline media, respectively. In addition, the catalyst shows outstanding stability for 48 hours in both acidic and alkaline media. The excellent catalytic activity originates from more active sites and greater electron conductivity bestowed by the carbon layer, which also improves the long-term stability in both acidic and alkaline solutions.

Nitrogen-Doped Mesoporous Molybdenum Carbide Nanosheets for Efficient Alkaline Hydrogen Production

“…37 Transmission electron microscopy (TEM) images of Mo 2 C@N-30 further displayed the flower-like morphology and ultrathin nanosheets at the edges of the sample (Figure 3b,c). High-resolution TEM images (Figure 3d) of Mo 2 C@N-30 with interplanar distances of 0.227 and 0.238 nm can be assigned to the (101) and (002) planes of β-Mo 2 C. 38,39 Besides, we can observe some black dots leading to a difference of morphological contrast, which implied that the periodic arrangement of the crystal structure might be disorganized owing to nitrogen atom doping. The electron diffraction (SAED) pattern (Figure 3e) also verified the phase of as-synthesized hexagonal Mo 2 C, the diffraction rings of (101), ( 102), (200), and (201) planes can be observed, and there are two diffraction spots that deviate from the rings as a result of distortion of crystal structure, well corresponding with XRD analysis.…”

Amorphous Co–Mo–P film on nickel foam: a superior bifunctional electrocatalyst for alkaline seawater splitting

“…Hydrogen, a renewable and storable energy carrier with net-zero emissions, is regarded as a potential candidate for conventional fossil fuel [1][2][3][4]. Exactly, the electrochemical water splitting could offer a promising and sustainable route to generate hydrogen on a large scale executed through two half-reactions of hydrogen and oxygen evolution reaction (HER/OER) [5][6][7][8][9].…”