CoW Bimetallic Carbide Nanocatalysts: Computational Exploration, Confined Disassembly–Assembly Synthesis and Alkaline/Seawater Hydrogen Evolution

Abstract

Earth‐abundant tungsten carbide exhibits potential hydrogen evolution reaction (HER) catalytic activity owing to its Pt‐like d‐band electronic structure, which, unfortunately, suffers from the relatively strong tungsten‐hydrogen binding, deteriorating its HER performance. Herein, a catalyst design concept of incorporating late transition metal into early transition metal carbide is proposed for regulating the metal–H bonding strength and largely enhancing the HER performance, which is employed to synthesize CoW bi‐metallic carbide Co6W6C by a “disassembly–assembly” approach in a confined environment. Such synthesized Co6W6C nanocatalyst features the optimal Gibbs free energy of *H intermediate and dissociation barrier energy of H2O molecules as well by taking advantage of the electron complementary effect between Co and W species, which endows the electrocatalyst with excellent HER performance in both alkaline and seawater/alkaline electrolytes featuring especially low overpotentials, elevated current densities, and much‐enhanced operation durability in comparison to commercial Pt/C catalyst. Moreover, a proof‐of‐concept Mg/seawater battery equipped with Co6W6C‐2‐600 as cathode offers a peak power density of 9.1 mW cm−2 and an open‐circuit voltage of ≈1.71 V, concurrently realizing hydrogen production and electricity output.

Thermal Shrinkage Engineering Enables Electrocatalysts for Stable Hydrogen Evolution at 2000 mA cm−2

“…Moreover, no obvious potential degradation at 2000 mA cm −2 in simulated alkaline seawater is detected for Ru‐Ni(OH) 2 ‐200 (Figure 5b), demonstrating its high durability for HER in simulated alkaline seawater. These results indicate the negligible influence of Na + and Cl − ions on the HER catalytic activity and durability, [ 51,52 ] revealing the practical application potential of Ni(OH) 2 ‐200. Moreover, the HER performance of Ru‐Ni(OH) 2 ‐200 in simulated alkaline seawater is superior to mostly reported catalysts (Table S3, Supporting Information).…”

Construction of CoP2-Mo4P3/NF Heterogeneous Interfacial Electrocatalyst for Boosting Water Splitting

“…To gain insight into the HER kinetics of the prepared electrocatalysts, the Tafel slope was obtained by fitting the linear region of Tafel plots as shown in Figure 3 c. The commercial PtC/NF exhibits an expected small Tafel slope of 56.7 mV dec −1 , which is close to the value reported in the literature. CoP 2 -Mo 4 P 3 /NF catalyst reveals a smaller Tafel slope of 86.6 mV dec −1 compared to Mo 4 P 3 /NF (97.3 mV dec −1 ), Co-MoO x /NF (123.6 mV dec −1 ), MoO x /NF (183.6 mV dec −1 ) and NF (216.3 mV dec −1 ), indicating its faster kinetics for HER and the corresponding Volmer-Heyrovsky mechanism, where the reaction rate is limited by the Heyrovsky step (H ads + H 3 O + + e − ⇌ H 2 + H 2 O) [ 29 ]. Additionally, CoP 2 -Mo 4 P 3 /NF has a larger exchange current density ( j 0 , calculated by the Tafel equation) of 14.71 mA cm −2 compared to that of PtC/NF ( j 0 = 7.38 mA cm −2 ), indicating its higher HER catalytic activity [ 14 ].…”

Recent progress in bimetallic carbide-based electrocatalysts for water splitting

“…59 Shi et al synthesized a Co 6 W 6 C bi-metallic carbide, featuring optimal Gibbs free energy of H* intermediates and dissociation barrier energy of H 2 O molecules, by taking advantage of the electron complementary effect between Co and W species, and the Co 6 W 6 C electrocatalyst exhibited excellent HER performance in both alkaline and seawater/alkaline electrolytes. 60…”

“…Bimetallic carbides, also defined as interstitial compounds, are actually solid solutions in which the solute metallic elements (e.g., Co/Ni/Fe/Zn/Ta/W/Mo) can be incorporated into the lattice spacing of monometallic carbides (e.g., W x C/Mo x C/Ti x C/ V x C). 42,60,[75][76][77][78] Bi-TMCs typically exhibit a specific crystalline structure, and the arrangement of metal and carbon atoms in the crystal lattice determines the coordination environment and electronic structure, further affecting the catalytic activity and stability. The interaction between different metals in catalysts leads to the formation of new crystal and electronic structures.…”