Exploration of bifunctional electrocatalysts toward effective oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is pivotal for developing high-efficiency and rechargeable metal-air batteries but remains great challenging. Here we elaborately synthesize lamellar-assembled PdNi super-nanosheets (SNSs) with an optimized Pd/Ni molar ratio to serve as attractive ORR and OER bifunctional electrocatalysts for rechargeable high-powered Zn-air batteries (ZABs). The products are layer-by-layer stackings of ultrathin PdNi nanosheet motifs. On the drastically extended two-dimensional (2D) surface, the inserted Ni atoms can substantially lower down the d-band center of surface Pd toward improved ORR kinetics and concurrently create oxytropic NiO_x sites to adsorb –OH groups for promoting the reverse OER electrocatalysis. Specifically, the ORR mass activity and specific activity of the primary Pd₉₂Ni₈ SNSs attain 2.5 A·mg⁻¹ and 3.15 mA·cm⁻², which are respectively 14 and 9 times those of commercial Pt/C. Meanwhile, the OER activity and stability of Pd₉₂Ni₈ SNSs/C distinctly outperform those of the RuO₂ benchmark, suggesting excellent reversible oxygen electrocatalysis. The power density of the ZAB with Pd₉₂Ni₈ SNSs/C as the air cathode is 2.7 times higher than that by Pt/C benchmark. Significantly, it can last for over 150 h without significant performance degradation during the charge–discharge cycle test. This work showcases a feasible strategy for developing self-assembled multimetallic 2D nanomaterials with excellent bifunctional catalytic performances toward energy conversion applications.

Platinum-based nanocrystals are the most effective electrocatalysts for accelerating the chemical transformations on the anode in direct alcohol fuel cells. To facilitate practical applications and overcome the drawbacks of diverse alcohols, it is significant to develop electrocatalysts with high activities and a wide fuel flexibility. Here, we demonstrate a practicable solution method for fabricating composition tunable trimetallic PtNiRu dendritic nanostructures (DNSs) which can serve as versatile and active catalysts for electrooxidation of a variety of liquid alcohols. A series of trimetallic DNSs with tunable Pt/Ni/Ru atomic ratios were successfully synthesized by simply adjusting the feeding of precursors. Detailed electrochemical test indicates that, among other compositions, the Pt₆₆Ni₂7Ru7 DNSs present much superior electroactivity in catalyzing electrooxidation of liquid alcohols in acidic mediums. Specifically, the mass activity and specific activity on the Pt₆₆Ni₂₇Ru₇ DNSs, for electrooxidation of methanol, ethanol, and ethylene glycol, are 4.57 and 4.34 times, 3.55 and 3.42 times, and 2.37 and 2.28 times that of the commercial Pt black, respectively. X-ray photoelectron spectroscopy and CO stripping studies reveal the adsorption of CO on these PtNiRu DNSs is much weaker than on pure Pt. Meanwhile, the surface Ru sites can provide neighbouring -OH groups to facilitate the oxidation and removal of the adsorbed intermediates (-CO) on the surface Pt sites, effectively improving the CO tolerance of the catalysts. The PtNiRu DNSs also show effectively boosted capacity for breaking the C-C bond in C₂-alcohols, showing great potential for fuel-flexible fuel cell applications.