Function of Doping Ru Element in the Hydrogen Evolution Reaction in Rare-Earth Transition-Metal Intermetallics

Abstract

Transition metal-based intermetallics are promising electrocatalysts for replacing the commercial Pt metal in the hydrogen evolution reaction (HER). In this work, RENi 2 and RERu 0.25 Ni 1.75 (RE = Pr, Tb, and Er) were synthesized and their electrocatalytic HER activities were explored. Among undoped compounds, PrNi 2 exhibits the best performance and requires an overpotential of 55 mV, while partially replacing Ni with Ru element (PrRu 0.25 Ni 1.75 ) can greatly reduce the overpotential to 20 mV at a current density of 10 mA/cm 2 . Such enhancement was recognized that belongs to their extrinsic property, and their intrinsic HER activities were similar after normalizing the electrocatalytic surface area. Further investigation on ScM 2 and ScRu 0.25 M 1.75 (M = Co and Ni) suggests that doping Ru element in ScCo 2 will significantly enhance antibonding character around the Fermi level (E F ) and weaken hydrogen adsorption energy. On the other hand, the antibonding population for ScNi 2 and ScRu 0.25 Ni 1.75 is similar at E F , which accounts for their close intrinsic HER activities.

Fe Engineering on Ru Nanosheets for Enhanced Hydrogen Evolution in pH-Universal Media

“…Ruthenium (Ru) is the most inexpensive element among noble metals. , Moreover, Ru possesses a comparable binding for hydrogen (65 kcal mol –1 ) as Pt (62 kcal mol –1 ). − Prior investigations suggest that engineering on size, dimension, and composition are effective to optimize the Ru property, for expediting hydrogen generation. − Volmer and Heyrovsky processes are the general rate-determining steps for nonacidic hydrogen production, which typically depend on the ability of water dissociation and hydrogen binding, respectively . Henceforth, ration design is desirable to reach high-performance Ru-based HER catalysts.…”

Dealloying-Induced Zeolite-like Metal Framework of AB2 Laves Phase Intermetallic Electrocatalysts

“…As revealed by the powder X-ray diffraction pattern (XRD) (Figure S2), these compounds belong to the C15 Laves phase (Strukturbericht designation) that adopted a MgCu 2 structural type with cubic space group Fd m . Notice that there is a clear right shift of ScCo 2 among four samples, which implies a small unit cell parameter based on Bragg’s law.…”

“…In the initial stage, it was demonstrated that the electrocatalytic HER activities of M Co 2 and M Ru 0.25 Co 1.75 ( M = Sc and Zr) follow the order ScRu 0.25 Co 1.75 > ZrRu 0.25 Co 1.75 > ScCo 2 > ZrCo 2 , which is not surprising based on our previous investigation (Figure S2c). The chronoamperometry (CA) measurement of these samples in 1.0 M KOH “appears” to be stable over a period of 12 h (Figure S2d). Notably, a significant amount of Sc ion (27.97 μmol/L, Table ) was detected in the electrolyte as compared with that of Co ion (3.00 μmol/L) for ScCo 2 after CA measurement.…”

“…There are tetrahedron subunits in Laves phase intermetallics that connect to each other via corner-sharing and build the open tunnel framework with cations located in the tunnel; a dealloying process removing the cations from the tunnel can create void structures and therefore expose additional interstitial sites (Figure a). Additionally, since the chemical composition of Laves phase intermetallics is highly flexible, one can incorporate various elements to substitute the iron triad (i.e., Fe, Co, and Ni) in the open tunnel framework, which allows manipulating the bonding scheme of metal–metal bonds, which will further alter the balance of adsorption/desorption (i.e., tunable electronic configuration) as well as the resulting activity …”

Function of Internal and External Fe in a Ni-Based Precatalyst System Toward Oxygen Evolution Reaction

“…After constructing the models of Ni 3 P and Ni 2 FeP, their total and partial density of states (TDOS and PDOS) were computed with Stuttgart TB-LMTO 4.7 program . The bonding strength and bonding character of the selected atomic interactions (<2.8 Å) were evaluated using the crystal orbital Hamiltonian populations (COHP) method. , The exchange-correlation energy was treated with the local density approximation (LDA) functional and spherical symmetry was assumed for the potential inside each Wigner–Seitz (WS) sphere . WS radii as well as k points were determined by default and k-space integrations were done using the tetrahedron method.…”