Platinum and Palladium Overlayers Dramatically Enhance the Activity of Ruthenium Nanotubes for Alkaline Hydrogen Oxidation

Abstract

Templated vapor synthesis and thermal annealing were used to synthesize unsupported metallic Ru nanotubes with Pt or Pd overlayers. By controlling the elemental composition and thickness of these overlayers, we obtain nanostructures with very high alkaline hydrogen oxidation activity. Nanotubes with a nominal atomic composition of Ru 0.90 Pt 0.10 display a surface-specific activity (2.4 mA/cm 2 ) that is 35 times greater than that of pure Ru nanotubes at a 50 mV overpotential and ∼2.5 times greater than that of pure Pt nanotubes (0.98 mA/cm 2 ). The surface-segregated structure also confers dramatically increased Pt utilization efficiency. We find a platinum-mass-specific activity of 1240 A/g Pt for the optimized nanotube versus 280 A/g Pt for carbon-supported Pt nanoparticles and 109 A/g Pt for monometallic Pt nanotubes. We attribute the enhancement of both area-and platinum-mass-specific activity to the atomic-scale homeomorphism of the nanotube form factor with adlayer-modified polycrystals. In this case, subsurface ligand and bifunctional effects previously observed on segregated, adlayer-modified polycrystals are translated to nanoscale catalysts.

Recent progress in the structure control of Pd–Ru bimetallic nanomaterials

“…Presently, there are continuous reports on the use of Pd–Ru solid-solution alloys with specific compositions for numerous applications, such as methanol electrooxidation,[82] ethanol electrooxidation,[83,84] glycerol oxidation and detection,[85] hydrogen oxidation,[86,87] benzoic acid hydrogenation,[54] and phenol hydrogenation. [88] For instance, Tang et al [54] have prepared an N-doped C-supported Ru–Pd solid-solution alloy with an average particle size of 3.6 nm by the ultrasound-assisted co-reduction method 54 .…”

Single‐Atom Ru Doping Induced Phase Transition of MoS2 and S Vacancy for Hydrogen Evolution Reaction

“…Recently, investigators discovered that Ru‐based catalysts can efficiently catalyze HER. Although Ru‐based nanoparticle, cluster and alloy catalysts have been reported to exhibit excellent activity similar to Pt, they do not show the maximum atomic efficiency of Ru…”

Bimetallic nickel-molybdenum/tungsten nanoalloys for high-efficiency hydrogen oxidation catalysis in alkaline electrolytes

“…Numerous PGMs, such as Pt, palladium (Pd), iridium (Ir), ruthenium (Ru), and rhodium (Rh,) have been studied for HOR in alkaline electrolytes 10 , 12 , among which Pt and Ir are particularly active and stable. Moreover, alloying PGMs with other metals can enable performance enhancements resulting from the modified surface structures; typical examples include PtNi 13 , PtRu 14 , Pt-coated Cu 15 , body-centered cubic PdCu 9 , and others 16 – 20 . In the quest to understand why the HOR reactivity in alkaline media is significantly slower than that in acid on PGMs, there has been extensive debate over whether such sluggish HOR kinetics in alkali is determined by hydrogen binding energy (HBE) or OH binding energy (OHBE)/oxophilicity 8 , 10 , 11 , 13 , 21 – 27 .…”