Fabrication of polyhedral Cu–Zn oxide nanoparticles by dealloying and anodic oxidation of German silver alloy for photoelectrochemical water splitting

A significant effort has been dedicated to the synthesis of Cu–Zn oxide nanoparticles as a robust photocathode material for photoelectrochemical water splitting. Cu–Zn oxide nanoparticles were formed by controlled anodization of German silver (Cu–Zn–Ni) alloy in an aqueous electrolyte. Scanning electron microscopy (SEM) demonstrates the dependence of the obtained nanostructures on the anodization time. The X-ray diffraction (XRD) patterns showed the formation of copper oxide (CuO) and zinc oxide (ZnO) nanoparticles with good stability. This was also confirmed by the compositional X-ray photoelectron spectroscopy (XPS) analysis. The obtained polyhedral nanoparticles showed high optical activity with adequate bandgap energy. These optimized nanoparticles achieved boosted photocurrent of − 0.55 mA/cm2 at − 0.6 V vs. SCE under AM 1.5 illumination, confirming the role of the optimized dealloying and thermal treatment in tuning the photoelectrochemical performance of the material

Propping the electrochemical impedance spectra at different voltages reveals the untapped supercapacitive performance of materials

Electrochemical impedance spectroscopy (EIS) is one of the most powerful and universal techniques that provides deep insights into the nature of the electrochemical system and its performance and limitations. Electric double layer capacitors (EDLCs) are electrochemical devices that can deliver and store large amounts of energy compared to traditional capacitors. The selection of an electrolyte is critical to the overall performance of EDLCs as it strongly influences the internal resistance, operating potential window, and rate capability of the device. Herein, fullerene C76 is investigated in four different electrolyte systems (Li2SO4, Na2SO4, K2SO4, and Rb2SO4) to reveal the crucial role of the electrolyte cation on the electrochemical supercapacitive performance. The Stern layer and diffuse layer formation are theorized for the electrolytes and comprehensively analysed to identify the electrolyte that provides the best system for high capacitive output. Rb+ is found to have the best conductivity and is the most responsive to applied potentials. Specifically, monitoring the EIS of the system at different applied voltages enables the unveiling of the ongoing electrochemical processes and the charge storage mechanism in detail. This approach can be generalized for various electrochemical energy storage systems to help design efficient systems and unveil the working mechanisms

Ternary Ti-Mo-Fe Nanotubes as Efficient Photoanodes for Solar-Assisted Water Splitting

Designing efficient and stable water splitting photocatalysts is an intriguing challenge for energy conversion systems. We report on the optimal fabrication of perfectly aligned nanotubes on trimetallic Ti-Mo-Fe alloy with different compositions prepared via the combination of metallurgical control and facile electrochemical anodization in organic media. The X-ray diffraction (XRD) patterns revealed the presence of composite oxides of anatase TiO2and magnetite Fe3O4with better stability and crystallinity. With the optimal alloy composition Ti-(5.0 atom %) Mo-(5.0 atom %) Fe anodized for 16 h, enhanced conductivity, improved photocatalytic performance, and remarkable stability were achieved in comparison with Ti-(3.0 atom %) Mo-(1.0 atom %) Fe samples. Such optimized nanotube films attained an enhanced photocatalytic activity of ∼0.272 mA/cm2at 0.9 VSCE, which is approximately 4 times compared to the bare TiO2nanotubes fabricated under the same conditions (∼0.041 mA/cm2at 0.9 VSCE). That was mainly correlated with the emergence of Mo and Fe impurities within the lattice, providing excess charge carriers. Meanwhile, the nanotubes showed outstanding stability with a longer electron lifetime. Moreover, carrier density variations, lower charge transfer resistance, and charge carriers dynamics features were demonstrated via the Mott-Schottky and electrochemical impedance analyses