Host–Guest Ensemble Effect on Dual-Pt atom-on-Rh Nanosheets Enables High-Efficiency and Anti-CO Alkaline Hydrogen Oxidation

Abstract

Explicit atomic coordinations of binary metal atoms on low-dimensional host–guest-type bimetallic nanomaterials can arouse unique ensemble effects and significantly improve the catalysis performances, but they confront a formidable challenge in chemical synthesis. Here, we draw on a thermoinduced secondary crystallization process of preprepared amorphous/crystalline hybrid ultrathin Rh nanosheets (NSs) to capture Pt atoms into the two-dimensional (2D) Rh lattice, by which precisely controlled Pt atomic dispersions from a single atom to dual atoms and to clustered atoms can be facilely elected and embedded into the ultrathin Rh hosts. Among them, the dual-Pt atom-on-Rh (denoted as Pt2–Rh) NSs exhibit an extremely high activity and an excellent CO tolerance for the alkaline hydrogen oxidation reaction (HOR), achieving a 18.5 times higher mass activity at 50 mV overpotential than that of commercial Pt/C. Theoretical studies indicate that the host–guest ensemble effect aroused by the specific pairwise Pt2-on-Rh coordination feature can moderately enhance both the surface *H and *OH bindings, which synergistically lower the free energy of the rate-determining Volmer step and thus promote the combination of neighboring *H and *OH to form H2O. Enhanced *H adsorption can also prevent the main available sites from being occupied by hydroxyl groups in alkaline conditions. The free energy diagram and anti-CO experiments coherently indicate that the oxidation of *CO by neighboring *OH to form *COOH is kinetically more favorable to proceed on the Pt2–Rh NSs, effectively preventing the catalysts from being poisoned. This work sheds light on the ensemble effect of host–guest heteroatom coordinations for designing high-efficiency alkaline HOR catalysts.

Breaking Surface Atomic Monogeneity of Rh2P Nanocatalysts by Defect‐Derived Phosphorus Vacancies for Efficient Alkaline Hydrogen Oxidation

“…In practical fuel cells, the presence of trace CO impurities in the industrial hydrogen supply can severely poison Pt-based anode HOR catalysts, which significantly reduces their lifetime. [45][46][47]…”

Recent Advances in Platinum Group Metal Based Alloys for Alkaline Hydrogen Oxidation Reaction

“…Recently, Xie et al reported the synthesis of amorphous/crystalline hybrid ultrathin Rh nanosheets (a/c-Rh NSs) with Pt atoms into the Rh lattice. [40] Interestingly, the Pt atomic dispersion can be precisely controlled from a single atom to dual atoms and further to clusters (Figure 4a). Among all the as-synthesized catalysts, the dual-Pt atom-on-Rh (Pt 2 -Rh) possesses the highest alkaline HOR activity due to its pairwise Pt 2 -on-Rh coordination feature that can induce a specific host-guest ensemble effect.…”

“…Zhang et al reported the synthesis of RhMo nanosheets (RhMo NSs) with metastable phase. [40] The RhMo NSs are actually a unique core/shell structure, of which the core is the metastable RhMo alloy in hexagonal close packed (HCP) phase and the shell is the stable RhMo alloy in FCC phase. RhMo NSs possess a significant large surface area due to the atomic thickness, which can provide abundant active sites.…”

Alleviating the competitive adsorption of hydrogen and hydroxyl intermediates on Ru by d–p orbital hybridization for hydrogen electrooxidation

“…Alkaline exchange membrane fuel cells (AEMFCs) are regarded as next-generation technology for hydrogen-to-electric energy conversion. 1–3 One of the most important advantages is that the electrocatalysts for the cathodic oxygen reduction reaction could get rid of the dependence on platinum group metals (PGMs) compared to the proton exchange membrane-based counterpart operated under harsh acidic conditions. 4–6 Nevertheless, the anodic hydrogen oxidation reaction (HOR) in high pH electrolytes suffers from more complex catalytic mechanisms and thus sluggish kinetics.…”