Mesoporous MoO_3–x Material as an Efficient Electrocatalyst for Hydrogen Evolution Reactions

Abstract

A unique approach for the synthesis of nonstoichiometric, mesoporous molybdenum oxide (MoO 3-x ) with nanosized crystalline walls by using a soft template (PEO-b -PS) synthesis method is introduced. The as-synthesized mesoporous MoO 3-x is very active and stable (durability > 12 h) for the electrochemical hydrogen evolution reaction (HER) under both acidic and alkaline conditions. The intrinsic MoO 3 serves as an HER electrocatalyst without the assistance of carbon materials, noble metals, or MoS 2 materials. The results from transmission electron microscopy and N 2 sorption techniques show that the as-synthesized mesoporous MoO 3-x has large accessible pores (20-40 nm), which are able to facilitate mass transport and charge transfer during HER. In terms of X-ray diffraction, X-ray photoelectron spectroscopy, temperature-programmed oxidation, and diffusive refl ectance UV-vis spectroscopy, the mesoporous MoO 3-x exhibits mixed oxidation states (Mo 5+ , Mo 6+ ) and an oxygen-defi cient structure. The as-synthesized MoO 3-x only requires a low overpotential (≈0.14 V) to achieve a 10 mA cm −2 current density in 0.1 M KOH and the Tafel slope is as low as 56 mV dec −1 . Density functional theory calculations demonstrate a change of electronic structure and the possible reaction pathway of HER. Oxygen vacancies and mesoporosity serve as key factors for excellent performance.

Self-catalyzed decomposition of discharge products on the oxygen vacancy sites of MoO3 nanosheets for low-overpotential Li-O2 batteries

“…In contrast, the high-resolution XPS spectrum of Mo 3d of MoO 3−x NSs-1 displays new peaks that attributed to the Mo 5+ (Fig. 2c) [45,46]. With increasing reduction time, the Mo 3d XPS spectrum of MoO 3−x NSs-2 in Fig.…”

A Perovskite Nanorod as Bifunctional Electrocatalyst for Overall Water Splitting

“…[18,27,43] As seen from Figure 5d, the C dl of SNCF-NR is more than twice larger than that of SNCF, implying higher ECSA of SNCF-NR. [51,52] Also, the O 2 2− /O − species were reported to be active for OER catalysis. Second, SNCF-NR possesses faster charge transfer rate.…”

Anderson Localization in 2D Amorphous MoO3‐x Monolayers for Electrochemical Ammonia Synthesis

“…From X‐ray photoelectron spectroscopy (XPS) for Mo 3d (see Figure c), four peaks of Mo 3d correspond to Mo 6+ (235.6 and 232.4 eV) and Mo 5+ (234.4 and 231.2 eV), respectively, and the presence of Mo 5+ can efficiently increase electron concentration, while there is no Mo 5+ in crystalline MoO 3 (Figure S1). Moreover, XPS measurements confirm the lower energy level (530.3 eV) of O1s, indicating the existence of oxygen vacancies (OVs) in 2D A‐MoO 3‐ x monolayers (Figure d) . The absorption in visible region is attributed to the localized surface plasmon resonance (LSPR) of 2D A‐MoO 3‐ x monolayers (Figure S2) .…”