Ultrathin N-Doped Mo₂C Nanosheets with Exposed Active Sites as Efficient Electrocatalyst for Hydrogen Evolution Reactions

Abstract

Probing competent electrocatalysts for hydrogen evolution reaction (HER) of water splitting is one of the most hopeful approaches to confront the energy and environmental crisis. Herein, we highlight ultrathin N-doped MoC nanosheets (N-MoC NSs) in the role of greatly efficient platinum-free-based electrocatalysts for the HER. The transformation of crystal phase and structure between MoO nanosheets with a thickness of ∼1.1 nm and N-MoC NSs with a thickness of ∼1.0 nm is studied in detail. Structural analyses make clear that the surfaces of the N-MoC NSs are absolutely encompassed by apical Mo atoms, hence affording an ideal catalyst prototype to expose the role of Mo atoms for the duration of HER catalysis. Theoretical calculations demonstrate that the nanosheet structure, N doping, and particular crystalline phase of MoC produce more exposed Mo active sites, including Mo atoms on the C plane and doped N atoms. Through detailed electrochemical investigations, N-MoC NSs possess HER activity with an onset potential of -48.3 mV vs RHE, Tafel slope of 44.5 mV dec, and overpotential of 99 mV vs RHE at the cathodic current density of 10 mA cm with excellent long-term stability. Lastly, the calcination temperature and dicyandiamide amount can obviously affect the phase transformation and surface structure of molybdenum carbide, resulting in an adjustable HER activity. This synthesis mechanism will facilitate the understanding and optimization of Mo-based electrocatalysts in the energy conversion field.

Fine Tuning Electronic Structure of Catalysts through Atomic Engineering for Enhanced Hydrogen Evolution

“…[11] To overcome these disadvantages, great efforts have been devoted to developing non-noble catalysts with highly efficient and stable HER catalytic activities, [12] including alloy, [13] transition-metal (TM) borides, [14,15] carbides, [16][17][18][19][20] nitrides, [20,21] oxides, [22] phosphides, [6,[23][24][25] and sulfides. [20,[31][32][33][34][35][36][37][38][39][40] The HER activity of Mo 2 C was first studied by Hu's group in 2012, which was convinced to be a promising catalyst for HER in both acidic and basic conditions. [20,[31][32][33][34][35][36][37][38][39][40] The HER activity of Mo 2 C was first studied by Hu's group in 2012, which was convinced to be a promising catalyst for HER in both acidic and basic conditions.…”

Beyond 1T‐phase? Synergistic Electronic Structure and Defects Engineering in 2H‐MoS2xSe2(1‐x) Nanosheets for Enhanced Hydrogen Evolution Reaction and Sodium Storage

“…To understand the origin for the enhanced HER catalytic activity in 2H‐MoS 2 x Se 2(1‐ x ) , the DFT calculations were performed to investigate the electronic structure and the hydrogen adsorption free energy ΔG H* (Figure ‐) . According to the results in Figure b, the 2H‐MoS 2 x Se 2(1‐ x ) are all semiconductors with the band‐gap computed to be 1.61 eV, 1.51 eV, and 1.44 eV for 2H‐MoS 2 , 2H‐MoSe 2 , and 2H‐MoS 0.2 Se 1.8 , respectively.…”

Fe@Fe2P Core‐Shell Nanorods Encapsulated in Nitrogen Doped Carbon Nanotubes as Robust and Stable Electrocatalyst Toward Hydrogen Evolution

“…The enhanced HER performance of Fe@Fe 2 P/NCNT was originated from the additional active sites from Fe 2 P estimated from the double-layer capacitances ( Figure S6), which was usually utilized to quantitatively analyze the electrochemical surface area (ESA) of HER electrocatalyst. [28] NCNT and Fe@Fe 2 O 3 /NCNT with Tafel slopes of 179.1 mV dec À 1 and 151 mV dec À 1 manifested the sluggish HER kinetics due the few active sites for HER. In order to confirm the higher intrinsic activity of Fe@Fe 2 P/NCNT electrocatalyst, TOF was calculated and Fe@Fe 2 P/NCNT possessed a higher TOF (0.173 s À 1 @overpotential = 200 mV) compared to that of Fe/ NCNT (0.072 s À 1 @overpotential = 200 mV) indicating the importance of Fe 2 P for boosting the HER activity.…”