Metallic WO₂–Carbon Mesoporous Nanowires as Highly Efficient Electrocatalysts for Hydrogen Evolution Reaction

Abstract

The development of electrocatalysts to generate hydrogen, with good activity and stability, is a great challenge in the fields of chemistry and energy. Here we demonstrate a "hitting three birds with one stone" method to synthesize less toxic metallic WO2-carbon mesoporous nanowires with high concentration of oxygen vacancies (OVs) via calcination of inorganic/organic WO3-ethylenediamine hybrid precursors. The products exhibit excellent performance for H2 generation: the onset overpotential is only 35 mV, the required overpotentials for 10 and 20 mA/cm(2) are 58 and 78 mV, the Tafel slope is 46 mV/decade, the exchange current density is 0.64 mA/cm(2), and the stability is over 10 h. Further studies, in combination with density functional theory, demonstrate that the unusual electronic structure and the large amount of active sites, generated by the high concentration of OVs, as well as the closely attached carbon materials, were key factors for excellent performance. Our results experimentally and theoretically establish metallic transition metal oxides (TMOs) as intriguing novel electrocatalysts for H2 generation. Such TMOs with OVs might be promising candidates for other energy storage and conversion applications.

Mo2C nanoparticles embedded within bacterial cellulose-derived 3D N-doped carbon nanofiber networks for efficient hydrogen evolution

“…As shown in Figure 3b, the Pt/C catalyst exhibits a Tafel slope of 30.8 mV dec − 1 , consistent with the reported values. 30,37,40 The Tafel slope of Mo 2 C@N-CNFs is 70.0 mV dec − 1 , which is much lower than that of reference catalysts such as CNFs (214.5 mV dec − 1 ), N-CNFs (195.4 mV dec − 1 ) and com-Mo 2 C (114.5 mV dec − 1 ), indicating a higher HER rate and favorable kinetics for Mo 2 C@N-CNFs. The Tafel slope value of Mo 2 C@N-CNFs falls within the range of 40-120 mV dec − 1 , suggesting that the HER taking place on the Mo 2 C@N-CNF surface follows a Volmer-Heyrovsky mechanism, and the rate of the discharge step is consistent with that of the desorption step.…”

“…At 1 bar and 300 K, TΔS is approximately − 0.205 eV. 19,30 The value of ΔE H* is calculated as ΔE H* = E tot − E sub − 1/2E H2 , where E tot and E sub are the energies of H absorbed systems and the clean given surface, respectively, and E H2 is the energy of molecular H 2 in the gas phase.…”

Electrocatalysts for Hydrogen Evolution in Alkaline Electrolytes: Mechanisms, Challenges, and Prospective Solutions

“…However, their carbides, sulfides and phosphides have been explored recently with good activity toward HER in alkaline electrolytes 57, 106, 116, 117, 118, 119, 120. As molybdenum carbides own the electronic structure similar to that of Pt and possess high resistance to corrosion in alkaline medium, it has attracted extensive research attention as efficient HER electrocatalysts,57 even though these catalysts need relatively large overpotential of 190–230 mV to achieve the appropriate current densities 99.…”

Recent Progress in Energy‐Driven Water Splitting

“…In the recent years, great efforts have also been made to develop binary or ternary non‐noble metals or oxides in water oxidation electrocatalysts (e.g. Fe,127 Ni‐Fe,128 Ni‐Co,129 Ni‐Fe‐Co130 and CaMn 4 O x 131) and non‐noble metal oxides, sulfides and phosphides water reduction electrocatalysts (MoO 3–x ,132 WO 2 ,133 WO 3 ,134 MoS 2, 135 WS 2 ,[[qv: 135b]] CoP,136 Co 2 P137 and Ni 2 P[[qv: 137a,138]]) for cost‐competitive electrocatalysis. The non‐noble metal electrocatalysts were also extended to bifunctional types such as TiN@Ni 3 N,139 Ni 3 Se 2 /Ni,140 CoO/CoSe 2 141 and CoMnO@CN142 for both HER and OER in overall water splitting.…”

“…Meanwhile, analogous structures such as WS 2 [[qv: 135b,154]] also provoked tremendous interest as HER electrocatalysts for water splitting. Besides, other oxides such as MoO 3–x ,132 WO 2 133 and WO 3 134 also exhibited promising performance toward HER. There are other molybdenum‐based nanostructures that were studied as HER electrocatalysts for water splitting, including MoB,155 Mo 2 C,155, 156 NiMoN x ,157 and Co 0.6 Mo 1.4 N 2 158…”