N-Doped Carbon Shells Encapsulated Ru-Ni Nanoalloys for Efficient Hydrogen Evolution Reaction

Unlocking the Effects of the RuCo Alloy Ratio on Alkaline Hydrogen Production

Understanding the interaction between Ru and Co components and the alloy ratio effects on the catalytic process is a technical challenge that requires a precise alloy structural design. This study proposes an effective stepwise annealing method for the construction of RuCo alloy-based electrocatalysts with varied Ru:Co ratios. Interestingly, as the concentration of Co in the first-step pyrolysis products increases, the secondary pyrolysis results in RuCo composites undergoing a transition from incomplete alloying to alloy ratios of 1:1, 1:2, and 1:8. When the alloy ratio is 1:1, more Run+ and Co0 transform into Ru0 and Co2/3+. In 1 M KOH, RuCo-0.6/NC demonstrates outstanding catalytic performance and durability even superior to that of commercial Pt/C, delivering a lower overpotential of 16 mV at 10 mA cm-2. DFT calculations reveal that the fast H2O dissociation and moderate H adsorption guarantee the superior activity of RuCo.

Well-defined Ni3N nanoparticles armored in hollow carbon nanotube shell for high-efficiency bifunctional hydrogen electrocatalysis

Alkaline H2-O2 fuel cells and water electrolysis are crucial for hydrogen energy recycling. However, the sluggish kinetics of the hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) in an alkaline medium pose significant obstacles. Thus, it is imperative but challenging to develop highly efficient and stable non-precious metal electrocatalysts for alkaline HOR and HER. Here, we present the intriguing synthesis of well-defined Ni3N nanoparticles armored within an N-doped hollow carbon nanotube shell (Ni3N@NC) via the conversion of a hydrogen-bonded organic framework (HOF) to metal-organic framework (MOF), followed by high-temperature pyrolysis. As-developed Ni3N@NC demonstrates exceptional bifunctionality in alkaline HOR/HER electrocatalysis, with a high HOR limiting current density of 2.67 mA cm-2 comparable to the benchmark 20 wt% Pt/C, while achieving a lead in overpotential of 145 mV and stronger CO-tolerance. Additionally, it achieves a low overpotential of 21 mV to attain a HER current density of 10 mA cm-2 with long-term stability up to 340 h, both exceeding those of Pt/C. Structural analyses and electrochemical studies reveal that the remarkable bifunctional hydrogen electrocatalytic performance of Ni3N@NC can be ascribed to the synergistic coupling among the well-dispersed small-sized Ni3N nanoparticles, chain-mail structure, and optimized electronic structure enabled by strong metal-support interaction. Furthermore, theoretical calculations indicate that the high-efficiency HOR/HER observed in Ni3N@NC is attributed to the strong OH- affinity, moderate H adsorption, and enhanced water formation/dissociation ability of the Ni3N active sites. This work underscores the significance of rational structural design in enhancing performance and inspires further development of advanced nanostructures for efficient hydrogen electrocatalysis.

Ruthenium-Manganese Solid Solution Oxide with Enhanced Performance for Acidic and Alkaline Oxygen Evolution Reaction

Proton exchange membrane water electrolysers and alkaline exchange membrane water electrolysers for hydrogen production suffer from sluggish kinetics and the limited durability of the electrocatalyst toward oxygen evolution reaction (OER). Herein, a rutile Ru0.75 Mn0.25 O2-δ solid solution oxide featured with a hierarchical porous structure has been developed as an efficient OER electrocatalyst in both acidic and alkaline electrolyte. Specifically, compared with commercial RuO2 , the catalyst displays a superior reaction kinetics with small Tafel slope of 54.6 mV dec-1 in 0.5 M H2 SO4 , thus allowing a low overpotential of 237 and 327 mV to achieve the current density of 10 and 100 mA cm-2 , respectively, which is attributed to the enhanced electrochemically active surface area from the porous structure and the increased intrinsic activity owing to the regulated Ru>4+ proportion with Mn incorporation. Additionally, the sacrificial dissolution of Mn relieves the leaching of active Ru species, leading to the extended OER durability. Besides, the Ru0.75 Mn0.25 O2-δ catalyst also shows a highly improved OER performance in alkaline electrolyte, rendering it a versatile catalyst for water splitting.

Ultrafast Microwave Synthesis of Ru-Doped MoP with Abundant P Vacancies as the Electrocatalyst for Hydrogen Generation in a Wide pH Range

Molybdenum phosphide (MoP) has received increasing attention for the hydrogen evolution reaction (HER) due to its Pt-like electronic structure and high electrical conductivity. In this work, a flake-like Ru-doped MoP with phosphorus vacancy (Ru-MoP-P_V) electrocatalyst is synthesized for the first time by a simple and rapid room-temperature microwave approach within 30 s. The created abundant phosphorus vacancies provide rich active sites and favor rapid electron transfer. The introduced Ru also enhances the catalytic activity of the synthesized electrocatalyst efficiently. Then, the designed Ru-MoP-P_V possesses low overpotentials for HER with 79, 100, and 161 mV in 1.0 M KOH, 0.5 M H₂SO₄, and 1.0 M phosphate-buffered saline to obtain 10 mA cm^-2. The Ru-MoP-P_V and NiFe-layered double hydroxide are used as the cathode and the anode, respectively, to drive water splitting and just need a low cell voltage of 1.6 V to achieve 10 mA cm^-2. This work provides a feasible way for the rapid production of metal phosphides for energy conversion and storage applications.