Single-Step Synthesis of W₂C Nanoparticle-Dispersed Carbon Electrocatalysts for Hydrogen Evolution Reactions Utilizing Phosphate Groups on Carbon Edge Sites

Abstract

A novel, one-step protocol for the selective synthesis of W 2 C nanoparticles from phosphotungstic acid (H 3 PW 12 O 40 ), a low-cost and commercially available tungsten compound, was developed. The nanoparticles had diameters of 1–50 nm and were dispersed on a carbon substrate. The W 2 C nanoparticles were prepared by a simple operation sequence, involving impregnation of carbon black with H 3 PW 12 O 40 followed by calcination at 1000 °C. X-ray diffraction study revealed the selective formation of the W 2 C phase in the samples prepared, whereas the tungsten carbide (WC) phase was present in the control prepared from H 2 WO 4 . Stable W 2 C nanoparticles were obtained using this method owing to the presence of phosphate at the interfaces between the W 2 C nanoparticles and the carbon substrates, which inhibited the diffusion of carbon atoms from the carbon substrates to the W 2 C nanoparticles, leading to the formation of WC. The W 2 C nanoparticles prepared showed an excellent catalytic activity for the hydrogen evolution reaction (HER), with low Tafel slopes of ∼50 mV/decade. The HER catalytic activity was notably high, being comparable to that of MoS 2 , which is a promising alternative to Pt. The present method can potentially be applied to produce highly effective, low-cost, Pt-free electrocatalysts for the HER.

Structural Design and Electronic Modulation of Transition‐Metal‐Carbide Electrocatalysts toward Efficient Hydrogen Evolution

“…The confinement formation of carbides on CNT surface was employed by Li and co‐workers to fabricate ultrasmall and phase‐pure W 2 C, which was highly active than the conventional phase of WC due to the greater density of state near the E F . Conventional approaches using gaseous carbon precursors (e.g., CH 4 ) are unable to yield W 2 C as the main product since the relative amount of carbon to tungsten precursor is out of control, and the carbon diffusion through the gas–solid interface into the tungsten lattice proceeds too fast to allow for phase engineering ( Figure a).…”

Synthesis of Mo2C and W2C Nanoparticle Electrocatalysts for the Efficient Hydrogen Evolution Reaction in Alkali and Acid Electrolytes

“…In addition, attaching Mo 2 C and W 2 C to a carbon matrix has been shown to produce high-rate charge transfer properties during HER and to alleviate surface aggregation (Pan et al, 2014; Youn et al, 2014; Wu et al, 2016). Previous reports suggested that the HER electrocatalytic performance of Mo 2 C- and W 2 C-based catalysts mainly results from the morphology (Ang et al, 2016; Ishii et al, 2016; Peng et al, 2017), crystalline phases (Wan et al, 2014; Lin et al, 2017), and composition (Yu et al, 2018; Zhang et al, 2018) of the catalysts and the synthetic protocol. However, the critical challenge is to design and develop carbide-based catalysts with comparable catalytic performance to Pt for practical applications.…”

“…Different methodologies have been used to prepare Mo 2 C and its hybrids for HER applications (Pu et al, 2016; Kou et al, 2018; Liang et al, 2019). Tungsten carbides can exist in different phases, such as WC, metastable W 2 C, and WC 1−x , but during the last decade, most researchers have exclusively focused on the WC phase instead of the W 2 C phase (Neylon et al, 1999; Ishii et al, 2016). W/WC synthesized by Kou et al (2019) showed an overpotential of 159 mV @ 10 mA cm −2 .…”

Synthesis of nano‐coral tungsten carbide/carbon fibers as efficient catalysts for hydrogen evolution reaction

“…W‐C materials have two main phases: WC and W 2 C. Numerous studies have reported the preparation of WC and WC‐W 2 C 21‐24 . Nevertheless, only a few studies have reported the preparation of W 2 C 25,26 . All the reported processes have limitations, such as high temperatures, complicated processes, dangerous materials, or low‐yield products.…”