In‐Plane Mott–Schottky Effects Enabling Efficient Hydrogen Evolution from Mo₅N₆‐MoS₂ Heterojunction Nanosheets in Universal‐pH Electrolytes

Abstract

Cost‐effective electrocatalysts for the hydrogen evolution reaction (HER) spanning a wide pH range are highly desirable but still challenging for hydrogen production via electrochemical water splitting. Herein, Mo5N6‐MoS2 heterojunction nanosheets prepared on hollow carbon nanoribbons (Mo5N6‐MoS2/HCNRs) are designed as Mott–Schottky electrocatalysts for efficient pH‐universal HER. The in‐plane Mo5N6‐MoS2 Mott–Schottky heterointerface induces electron redistribution and a built‐in electric field, which effectively activates the inert MoS2 basal planes to intrinsically increase the electrocatalytic activity, improve electronic conductivity, and boost water dissociation activity. Moreover, the vertical Mo5N6‐MoS2 nanosheets provide more activated sites for the electrochemical reaction and facilitate mass/electrolyte transport, while the tightly coupled HCNRs substrate and metallic Mo5N6 provide fast electron transfer paths. Consequently, the Mo5N6‐MoS2/HCNRs electrocatalyst delivers excellent pH‐universal HER performances exemplified by ultralow overpotentials of 57, 59, and 53 mV at a current density of 10 mA cm−2 in acidic, neutral, and alkaline electrolytes with Tafel slopes of 38.4, 43.5, and 37.9 mV dec−1, respectively, which are superior to those of the reported MoS2‐based catalysts and outperform Pt in overall water splitting. This work proposes a new strategy to construct an in‐plane heterointerface on the nanoscale and provides fresh insights into the HER electrocatalytic mechanism of MoS2‐based heterostructures.

Enhanced Activities in Alkaline Hydrogen and Oxygen Evolution Reactions on MoS2 Electrocatalysts by In‐Plane Sulfur Defects Coupled with Transition Metal Doping

“…Among the common transition metalbased electrocatalysts such as sulfides, carbides, phosphides, and nitrides, [8][9][10][11][12][13] 2D molybdenum disulfide (MoS 2 ) has attracted much attention because of the earth's abundance and Pt-like hydrogen adsorption free energy (ΔG H* ). [14][15][16][17][18][19] However, the HER activity of MoS 2 is limited by the small number of unsaturated edge sites and poor intrinsic conductivity. [20][21][22][23] It is demonstrated that S-vacancies (S v ) in the inert basal plane can enhance the HER kinetics by exposing more unsaturated S-Mo bonds to optimize ΔG H* on the MoS 2 surface and various strategies have thus been proposed to generate S v in the basal plane, for example, etching with H 2 O 2 , [24] NaClO, [25] oxygen plasma treatment, [26] as well as H 2 annealing.…”

Hierarchically structured nickel/molybdenum nitride heterojunctions as superior bifunctional electrodes for overall water splitting

“…The construction of heterojunctions can afford a larger surface area, accelerate the electron transfer at the interface and regulate the adsorption free energy of reaction intermediates. [29][30][31][32] Thus, the rational design of bimetallic heterojunctions is a promising approach to boost the catalytic activity of metal nitrides. Recently, nickel nitride-based heterojunctions are widely developed, such as Ni 3 N/Co 2 N, NiMoN/ Ni 3 N, and Ni 3 N/W 5 N 4 heterostructures, and Ni 0.2 Mo 0.8 N/Fedoped Ni 3 N nanosheet arrays, exhibiting promising catalytic activity for water splitting.…”

Interface modifications for RuO2-decorated MoS2nanosheets as excellent electrocatalysts for alkaline hydrogen evolution reactions

“…3(a)) spectrum of MoS 2 is assigned to two strong peaks at 162.3 and 163.5 eV, consistent with S 2p 3/2 and S 2p 1/2 , respectively. 38 Differently, the peaks of Mo 3d and S 2p of the RuO 2 /MoS 2 catalyst both shift positively with a new peak at 235.2 eV assigned to Mo 6+ and a new signal at 168.4 eV attributed to SO 4 , 2–40 which suggests that electrons transfer from MoS 2 to RuO 2 nanoparticles, resulting from the intense electronic coupling effect generated from interface modifications. Furthermore, in the Ru 3d spectrum of the RuO 2 /MoS 2 catalyst (Fig.…”

“…Compared to the Raman peaks of MoS 2 , RuO 2 /MoS 2 displays a red-shift, which demonstrates the formation of an interface between RuO 2 nanoparticles and MoS 2 nanosheets with strong electronic interaction. 9 The chemical compositions and valence state were examined in depth by X-ray photoelectron spectroscopy (XPS). The full-scan X-ray photoelectron spectroscopy of the RuO 2 /MoS 2 catalyst confirms the coexistence of the Mo, S, Ru, and O elements (Fig.…”