WSe₂ and W(Se_xS_1−x)₂ nanoflakes grown on carbon nanofibers for the electrocatalytic hydrogen evolution reaction

Abstract

Transition metal dichalcogenides (TMD) have recently attracted substantial attention due to their potential application to the catalysis of the hydrogen evolution reaction (HER). In this study, triangular WSe2 and W(SexS1-x)2 nanoflakes uniformly dispersed on the surface of electrospun carbon nanofiber mats were synthesized in a chemical vapor deposition (CVD) system. The morphology and structure of these products were systematically characterized, revealing that WSe2 nanoflakes are configured in the 2H phase with high crystallinity, and the W(SexS1-x)2 nanoflakes are configured in the alloy form without any obvious phase separation. The hybrid catalyst mats were directly used as hydrogen evolution cathodes to investigate their HER activity. Excellent HER performances, including low overpotential, high current density and longterm stability, were achieved by optimizing the content of the initial W precursor and the appropriate substitution of selenium with sulfur, which was resulted from the appropriate cover density and thickness of the WSe2 nanoflakes and the defective structure of the W(SexS1-x)2 nanoflakes.

Vanadium carbide nanoparticles encapsulated in graphitic carbon network nanosheets: A high-efficiency electrocatalyst for hydrogen evolution reaction

“…The proton discharge reaction is fast and H 2 is evolved in a rate-determining combination reaction or Tafel step [48,49]. With regard to VC-NS, the Tafel slope is 56 mV dec À 1 , which is comparable to those of MoP, MoC x and CoP/Ti [44,46,50] but smaller than those of WS 2 , MoS 2 , Mo 2 N, MoSe 2 , and WSe 2 -C [40,45,51,52], listed in Table S2, indicating that HER occurs via a Volmer-Heyrovsky HER mechanism and electrochemical desorption is the rate-limiting step [48,49], The exchange current densities j 0 (defined as the current density at zero overpotential) of the electrocatalysts determined from the Tafel plots by extrapolation are listed in Table S1. VC-NS shows a j 0 value of 0.193 mA cm À 2 which is larger than that of VC-P of 0.092 mA cm À 2 .…”

“…VC-NS shows a small overpotential η 1 (defined as the overpotential at a current density of 1 mA cm À 2 as shown in Table S1) of 40 mV (vs. RHE, all the potentials are referenced to RHE in this work) which is less than those of Mo 2 C/CNT (64 mV) [37], mechanically activated MoS 2 (103 mV) [38], NiMoN x /C ( $ 160 mV) [39], and pure Mo 2 C (340 mV) [37] as listed in Table S2. Even at a current density of 10 mA cm À 2 , VC-NS shows an overpotential of only 98 mV which is much lower than that of common HER electrocatalysts such as WSe 2 nanoflakes on carbon nanofibers (158 mV) [40], Co 2 P (134 mV) [41], CoS 2 nanowires (145 mV) [42], Ni 2 P particles (121 mV) [43], porous MoC x (142 mV) [44], γ-Mo 2 N (381 mV) [45], MoB ( $ 220 mV) [6], and c-MoC (293 mV) [45] as shown in Table S2. To investigate the effects of the carbon network on the HER activity of VC-NS, the polarization curve of pure carbon prepared by the same method as VC-NS but using only Mg and NaHCO 3 as precursors is presented in Fig.…”

Transition Metal Selenides for Electrocatalytic Hydrogen Evolution Reaction

“…created the W(Se x S 1− x ) 2 nanoflakes with numerous defective basal planes though sulfur doping supported on carbon nanofiber mats (CFMs). Consequently, both of two materials exhibited low overpotential, high exchange current density and long‐term stability for the HER …”

“…Consequently, both of two materials exhibited low overpotential, high exchange current density and long-term stability for the HER. [62] Except for above four commonly used single transition metal selenides, some other TMSs have been reported for catalytic of HER. For example, Kukunuri et al investigated the activity of several palladium selenide (Pd 4 Se, Pd 17 Se 15 , Pd 7 Se 4 ) for HER.…”

WO3–x Nanoplates Grown on Carbon Nanofibers for an Efficient Electrocatalytic Hydrogen Evolution Reaction

“…The defects in the crystal structure served as active sites and dramatically improved the electrocatalytic HER performance. 28 As discussed above, typically, oxygen vacancies are active sites of tungsten oxides for HER. 6 Subsequently, in the present investigations, we proposed a facile method to fabricate oxygen vacancies-abundant WO 3-x catalysts in carbon nanofibers via carbon thermal reduction reaction at high temperature.…”