We present a facile route to fabricate novel nanoporous bimetallic Pt–Au alloy nanocomposites by dealloying a rapidly solidified Al₇₅Pt₁₅Au₁₀ precursor under free corrosion conditions. The microstructure of the precursor and the as-dealloyed sample was characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and energy dispersive X-ray (EDX) analysis. The Al₇₅Pt₁₅Au₁₀ precursor is composed of a single-phase Al₂(Au,Pt) intermetallic compound, and can be fully dealloyed in a 20 wt.% NaOH or 5 wt.% HCl aqueous solution. The dealloying leads to the formation of the nanoporous Pt₆₀Au₄₀ nanocomposites (np-Pt₆₀Au₄₀ NCs) with an fcc structure. The morphology, size and crystal orientation of grains in the precursor can be conserved in the resultant nanoporous alloy. The np-Pt₆₀Au₄₀ NCs consist of two zones with distinct ligament/channel sizes and compositions. The formation mechanism of these np-Pt₆₀Au₄₀ NCs can be rationalized based upon surface diffusion of more noble elements and spinodal decomposition during dealloying. Electrochemical measurements demonstrate that the np-Pt₆₀Au₄₀ NCs show superior catalytic activity towards the electro-oxidation of methanol and formic acid in the acid media compared to the commercial JM-Pt/C catalyst. This material can find potential applications in catalysis related areas, such as direct methanol or formic acid fuel cells. Our findings demonstrate that dealloying is an effective and simple strategy to realize the alloying of immiscible systems under mild conditions, and to fabricate novel nanostructures with superior performance.

In the present work, a green and simple strategy has been proposed to fabricate novel bi-modal nanoporous bimetallic Pt–Au alloy by electrochemical dealloying of a ternary Al₇₅Pt₁₅Au₁₀ precursor in a neutral sodium chloride solution. The Al₇₅Pt₁₅Au₁₀ precursor is composed of a single Al₂(Pt,Au) phase with lattice vacancies inside. The bi-modal nanoporous Pt–Au alloy exhibits an island-channel structure and the islands show an ultrafine three-dimensional bicontinuous interpenetrating ligament-channel (∼3.5 nm) characteristic. The dealloying mechanism of the precursor and the formation of the nanoporous structure have been addressed using electrochemical measurements (potentiodynamic and potentiostatic polarization) and microstructural analysis (scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray analysis). The dealloying at the low potential of −0.4 V vs.Ag/AgCl is associated with the partial dissolution of Al and the disappearance of the vacancies, leading to the formation of the stoichiometric Al₂(Pt,Au). The subsequent dealloying at 0.6 V vs.Ag/AgCl is related to the complete dissolution of Al and surface diffusion of Pt/Au, resulting in the formation of the ultrafine nanoporous structure. Besides, the bi-modal nanoporous Pt–Au alloy shows superior catalytic activity towards the electro-oxidation of formic acid in the acid media in comparison to the commercial JM-Pt/C catalyst. Our present findings provide implications for green synthesis of novel multi-functional nanoporous alloys through the electrochemical dealloying strategy in benign neutral salt solutions under mild conditions.

Mesoporous Ag/TiO ₂ nanocomposites fabricated by dealloying/calcination show superior photocatalytic performance under visible light as well as UV irradiation.

The CoCrFeNi high-entropy alloy coatings (HEACs) with different weight ratios (10 and 30 wt.%) of WC additions have been prepared using mechanical alloying and a vacuum hot pressing sintering technique on a Q235 steel substrate. The microstructures, microhardness, wear resistance, and corrosion resistance of HEACs were studied. The CoCrFeNi(WC) powders were obtained by mixing the CoCrFeNi HEA powders and WC particles. The sintered products of both HEACs with high relative density contained one solid solution phase with face-centered cubic structure, WC, and unknown precipitate phases. The transition boundary had a good metallurgical bonding with the coating and substrate. The average microhardness values of CoCrFeNi HEACs with 10 and 30 wt.% WC additions reached 475 and 531 HV respectively, which were far higher than that of the substrate (160 HV). Moreover, both coatings exhibited better wear resistance than the substrate under the same wear conditions. The 30 wt.% WC HEAC displayed the lower friction coefficient, and the shallower wear groove depth. The grain refinement strengthening and second-phase particle strengthening could be beneficial to the enhanced hardness and wear resistance of coatings with WC additions. The corrosion behavior of the tested samples in the 3.5 wt.% NaCl solution were investigated using electrochemical polarization measurements. The CoCrFeNi(WC) coatings all revealed the improved corrosion resistance. Especially, a 10 wt.% WC addition remarkably enhanced the comprehensive corrosion resistance and easy passivation of CoCrFeNi HEAC.