Optimizing Hydrogen Binding on Ru Sites with RuCo Alloy Nanosheets for Efficient Alkaline Hydrogen Evolution

Abstract

Ruthenium (Ru)‐based catalysts, with considerable performance and desirable cost, are becoming highly interesting candidates to replace platinum (Pt) in the alkaline hydrogen evolution reaction (HER). The hydrogen binding at Ru sites (Ru−H) is an important factor limiting the HER activity. Herein, density functional theory (DFT) simulations show that the essence of Ru−H binding energy is the strong interaction between the 4normaldz2 orbital of Ru and the 1s orbital of H. The charge transfer between Ru sites and substrates (Co and Ni) causes the appropriate downward shift of the 4normaldz2 ‐band center of Ru, which results in a Gibbs free energy of 0.022 eV for H* in the RuCo system, much lower than the 0.133 eV in the pure Ru system. This theoretical prediction has been experimentally confirmed using RuCo alloy‐nanosheets (RuCo ANSs). They were prepared via a fast co‐precipitation method followed with a mild electrochemical reduction. Structure characterizations reveal that the Ru atoms are embedded into the Co substrate as isolated active sites with a planar symmetric and Z‐direction asymmetric coordination structure, obtaining an optimal 4normaldz2 modulated electronic structure. Hydrogen sensor and temperature program desorption (TPD) tests demonstrate the enhanced Ru−H interactions in RuCo ANSs compared to those in pure Ru nanoparticles. As a result, the RuCo ANSs reach an ultra‐low overpotential of 10 mV at 10 mA cm−2 and a Tafel slope of 20.6 mV dec−1 in 1 M KOH, outperforming that of the commercial Pt/C. This holistic work provides a new insight to promote alkaline HER by optimizing the metal‐H binding energy of active sites.

Simultaneous optimization of CoIr alloy nanoparticles and 2D graphitic-N doped carbon support in CoIr@CN by Ir doping for enhanced oxygen and hydrogen evolution reactions

“…All these conrm that the conductivity inuenced by N type in the support can greatly enhance the catalytic performance owing to better charge transfer capacity, especially the higher graphitic N content. To estimate the relative activity of electrocatalysts, ECSA was evaluated by the C dl measurement from CV curves at different scan rates (10,20,40,60,80, 100 and 120 mV s À1 ) (Fig. S9 †).…”

“…In general, transition metal alloys with trace of noble metals are believed to be potential candidates to simultaneously lower the cost and improve the catalytic properties. [10][11][12][13] A CoIr alloy with trace of precious Ir based on the abundance of Co, which possesses favorable electronic properties for the OER and Pt-like electron states for the HER, is capable of promoting both OER and HER processes. [14][15][16][17] Because of distinct electronegativity and atomic radii for different metal atoms, the d-band center of Co would be modied to locate in the vicinity of the Fermi level owing to the Ir incorporation, which can moderate the intermediate adsorption free energy to reduce the OER/HER barrier.…”

Effect of Surface‐Adsorbed and Intercalated (Oxy)anions on the Oxygen Evolution Reaction

“…[4][5][6] However, under the harsh OER conditions, only certain oxidic phases are stable, e.g., layered nickel, iron, cobalt oxides/oxyhydroxides in alkaline media (we note that these phases, especially monometallic iron ones, potentially suffer from slow dissolution). [4][5][6][7][8][9] For example, transition metal chalcogenides or pnictides will transform to transition metal oxides/oxyhydroxides, while the chalcogenide or pnictide anion (X nÀ ) will be fully oxidized to the respective oxyanions (XO 4 2À and XO 4 3À , see Pourbaix diagrams in reference [10]). [4][5][6] Due to the high water-solubility of such oxyanions, they leach into the electrolyte.…”

Acetate promotes the formation of NiRu/NiO towards efficient hydrogen evolution

“…11 Among the various noble metals, ruthenium (Ru) has stimulated huge research interests, due to its relatively low price, and promising HER activities. 12,13 Metal-organic frameworks (MOFs), constructed via linking metal-containing nodes with organic ligands, is an emerging family of porous crystalline materials. 14 Owning to the fascinating features such as high porosity, large surface area, coordinatively unsaturated surface atoms, and tunable structure, etc., some pristine MOFs have been demonstrated as efficient electrocatalysts in water electrolysis.…”

“…11 Among the various noble metals, ruthenium (Ru) has stimulated huge research interests, due to its relatively low price, and promising HER activities. 12,13…”