Mo Doping Induced More Active Sites in Urchin‐Like W₁₈O₄₉ Nanostructure with Remarkably Enhanced Performance for Hydrogen Evolution Reaction

Abstract

Exploring highly efficient and inexpensive hydrogen evolution reaction (HER) electrocatalysts for various electrochemical energy conversion technologies is actively encouraged. Herein, a 3D urchin‐like Mo‐W18O49 nanostructure as an efficient HER catalyst is reported for the first time. The obtained Mo‐W18O49 catalyst exhibits excellent electrocatalytic activity toward HER with small onset potential and Tafel slope. The prepared Mo‐W18O49 electrode shows excellent durability after a long period. Density functional theory calculations reveal that the remarkably enhanced performance of Mo‐W18O49 can be due to the ability of Mo dopant to increase the number of active sites, leading to optimal hydrogen adsorption on the active sites because of the electronic and geometric modulation. In addition, the urchin‐like 3D morphology with a high surface area and abundant 1D nanowires promotes electron transfer, thereby ensuring fast interfacial charge transfer to improve electrocatalytic reactions. All these experimental and theoretical results clearly reveal that Mo‐W18O49 intrinsically improves HER activity and thus has potential applications in water splitting.

W‐Doped MoO2/MoC Hybrids Encapsulated by P‐Doped Carbon Shells for Enhanced Electrocatalytic Hydrogen Evolution

“…In parallel, the peaks at 229.8, 231.5 and 233.0 eV are attributable to Mo 4+ , Mo 5+ and Mo 6+ , which are assignable to MoO 2 and MoO 3 . Three peaks can be seen in the O 1s XPS spectra (Figure c) for all the samples, which can be attributed to O−Mo (530.8 eV), oxygen vacancies (531.7 eV) and O−C (533.0 eV), respectively. The high‐resolution XPS spectrum of C 1s (Figure d) for all the samples can be regarded as C−Mo (284.3 eV), C−C/C=C (284.8 eV), C−P (285.1 eV) and C−O (286.3 eV), respectively.…”

“…It is shown that the performance of W‐MoO 2 /MoC@PC ( η 20 =209 mV) is superior to that of Mo 2 C/C‐lamellas ( η 20 =220 mV), Mo x C‐G hybrids ( η 4 =475 mV), Mo 2− x Fe x C ( η 5 =240 mV), commercial Mo 2 C particles ( η 20 =225 mV), Mo 2 C nanoparticles supported on XC‐72R carbon black ( η 8 =200 mV), Mo 2 C nanowires ( η 20 =220 mV) and Mo 2 C nanosheets ( η 20 =260 mV) synthesized via pyrolysis of their MoO x /pphenylenediamine hybrid precursors, MoWON/NGR ( η 20 =270 mV) and so on. The performance of W‐MoO 2 /MoC@PC is inferior to that of Co 6 Mo 6 C‐G ( η 20 =183 mV), Mo‐W 18 O 49 ( η 20 =75 mV), MoO 2 @PC‐RGO ( η 20 =90 mV), NiMo‐NGTs ( η 20 =79 mV), and so on. The comparison reveals that W‐MoO 2 /MoC@PC exhibits comparable HER catalytic activity in comparison with most other Mo‐based nanostructures.…”

“…Three peaks can be seen in the O 1s XPS spectra (Figure c) for all the samples, which can be attributed to O−Mo (530.8 eV), oxygen vacancies (531.7 eV) and O−C (533.0 eV), respectively. The high‐resolution XPS spectrum of C 1s (Figure d) for all the samples can be regarded as C−Mo (284.3 eV), C−C/C=C (284.8 eV), C−P (285.1 eV) and C−O (286.3 eV), respectively. The high‐resolution W 4f spectra (Figure e) of W‐MoO 2 /MoC@PC and W‐MoO 2 /MoC/PC can be deconvoluted into three pairs of peaks; the difference of the BE between the two peaks in a doublet in the W 4f window is 2.1 eV, the intensity ratio is 4:3, and the FWHM is 1:1.…”

“…Recently, doping cations in Mo (W)‐based compounds has been studied to enhance the catalytic performance in comparison with their individual composite, such as post transition metals (e.g. Fe, Co, Ni) doped molybdenum carbides, Mo‐doped W 18 O 49 , etc. In this regards, it's highly desired for an efficient strategy to develop a facile, mild, and large‐scale approach to obtain W‐doped Mo‐based materials and serve as an efficient electrocatalyst for HER.…”

Vacancy Engineering of Iron‐Doped W18O49 Nanoreactors for Low‐Barrier Electrochemical Nitrogen Reduction

“…Considering this, defect‐rich W 18 O 49 , the only nonstoichiometric oxide composition of tungsten that can be isolated in a pure phase, might be an ideal candidate due to its intrinsically weak binding with hydrogen . In this case, however, the main challenges turn out to be: 1) maximizing the exposure of possible active sites (i.e., the W sites) and 2) the activation of N≡N to accelerate the sluggish NRR kinetics.…”