Abstract
In this paper, we report that WOx containing nanoalloys exhibit stable electrocatalytic performance in alkaline media, though bulk WO3 is easy to dissolve in NaOH solution. Carbon supported oxide-rich Pd–W alloy nanoparticles (PdW/C) with different Pd:W atom ratios were prepared by the reduction–oxidation method. Among the catalysts, the oxide-rich Pd0.8W0.2/C (Pd/W = 8:2, atom ratio) exhibits the highest catalytic activity for the oxygen reduction reaction. The X-ray photoelectron spectroscopy data shows that ~40% of Pd atoms and ~60% of the W atoms are in their oxide form. The Pd 3d5/2 binding energy of the oxide-rich Pd–W nanoalloys is higher than that of Pd/C, indicating the electronic structure of Pd is affected by the strong interaction between Pd and W/WO3. Compare to Pd/C, the onset potential of the oxygen reduction reaction at the oxide-rich Pd0.8W0.2/C shifts to a higher potential. The current density (mA·mg Pd−1) at the oxide-rich Pd0.8W0.2/C is ~1.6 times of that at Pd/C. The oxide-rich Pd0.8W0.2/C also exhibits higher catalytic stability than Pd/C, which demonstrates that it is a prospective candidate for the cathode of fuel cells operating with alkaline electrolyte.
Highlights
The study of the oxygen reduction reaction (ORR) has a history of more than one century sinceGrove fabricated the earliest hydrogen–oxygen fuel cell with Pt as the catalyst for ORR in 1839.In recent years, the studies of ORR have been promoted by the increasing demand of clean energy technology like fuel cells
Various electrocatalysts for ORR have been developed, including but not limited to Pt-based catalysts [3,4,5], Pd-based catalysts [6,7], catalysts based on non-precious metals [8,9], catalysts based on carbon nanostructure/nanocomposites [10,11,12,13], catalysts based on metal oxides [14,15], catalysts based on metal–organic frameworks [16,17], catalysts based on complexes [18,19], enzyme-based catalysts [20,21,22,23,24], metal carbides [25,26,27,28], and so on
Carbon black is the most used support for noble metal electrocatalysts in fuel cells, Pd-based electrocatalysts supported on carbon black (C) for ORR in alkaline media have been rarely reported over the past few years
Summary
The study of the oxygen reduction reaction (ORR) has a history of more than one century since. Carbon black is the most used support for noble metal electrocatalysts in fuel cells, Pd-based electrocatalysts supported on carbon black (C) for ORR in alkaline media have been rarely reported over the past few years. The new studies about carbon-black supporting Pd based catalysts for ORR in alkaline media have to face the difficult situation of being compared to the ultra-high active catalyst Pd/C. Bulk WO3 crystal can be dissolved in strong NaOH solutions, which limits its direct application in fuel cells operating with alkaline electrolytes To solve this problem, we started by separating the W atoms with noble metals such as Pd in the atomic scale before their oxidation.
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