Abstract
Bimetallic catalysts due to the synergistic effects often outperform their single-component counterparts while exhibiting structure and composition-dependent enhancement in active sites, thereby having the potential to improve the current density and over-potential parameters in the water oxidation reaction. Herein, we demonstrate a simple and rapid, yet highly efficient method to fabricate Pd–CoO films of immaculate homogeneity as characterized using different imaging and spectroscopic techniques. The SEM images revealed that the films were composed of bimetallic spherical granules wherein both metals were uniformly distributed in an atomic ratio of ~ 1:1. The time-dependent investigations of the film fabrication behavior demonstrated that the films formed in shorter deposition times (1–2 h) display more porous character, allowing better access to the reaction centers. This character was transcribed into their enhanced electrocatalytic performance toward the oxygen evolution reaction (OER). Using this specific bimetallic formulation, we could attain a low over-potential of 274 mV for a current density of 10 mA cm−2, whereas the high current density value of > 200 mA cm−2 was achieved while still under 600 mV of over-potential. The cycling and current generation stability was also found to be sufficiently high, which can only be attributed to the facile electron transfer processes and a higher number of active sites available in homogeneous bimetallic films.
Highlights
Electrocatalytic water oxidation is an extensively studied reaction due to its importance in industrial water splitting for hydrogen-based economy[1]
The materials with the ability to catalyze this reaction are of high significance for water splitting based hydrogen g eneration[5,6], and for oxygen evolution reactions (OER) in metal-air b atteries[7,8], or other oxidation reactions such as the oxidation of C O9 for the purification of hydrogen fuel obtained via currently accustomed fossil fuels based production
Bimetallic Pd–CoO thin films were synthesized by a facile single-step aerosol assisted chemical vapor deposition (AACVD) procedure, which is based on the generation of aerosol from the precursor solution and depositing the metal/metal oxide components over pre-heated substrates, as shown in our previous work[24,31]
Summary
Electrocatalytic water oxidation is an extensively studied reaction due to its importance in industrial water splitting for hydrogen-based economy[1]. It has been theoretically shown that CoOx/Pd(100) thin films based model systems in an ultra-high vacuum tend to induce novel structures and peculiar chemical attributes especially related to the Pd m etal[22] It has been demonstrated in the same work that the CoOx combination with the Pd can provide an activity comparable to pure Pd, but without the poisoning of Pd-metal due to the presence of oxide content. Films were fabricated on plain glass substrates for structural and morphological characterization using SEM/EDX, XRD, and XPS, showing a well-defined, granular structure composed of Pd and Co materials in highly homogenous distribution This structural and distributional homogeneity is correlated to the electrochemical performance in catalyzing the oxygen evolution reaction in water splitting. This work highlights the benefits of using AACVD in fabricating the films of various metal/metal oxide combinations at ease with exotic morphologies and desired catalytic attributes to be utilized in various applications
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