Highly ordered, Ni(OH)2-Ni-nanowire-based receptor elements were electrochemically fabricated and tested for formaldehyde (HCHO) detection by monitoring their oxidation ability in alkaline media. In order to normalize the electrochemical output currents, the Ni nanowires' electrochemically active surface area was assessed using an oxalate-based method after the template was released. The electrochemical transformation of the Ni-nanowire surfaces to a Ni(OH)2/NiOOH redox couple was performed in 0.5-mol/L KOH using cyclic voltammetry at 200?mV/s. The transformation was monitored for two cases: without KOH modification and with KOH-modified Ni nanowires. It was shown that the non-modified Ni nanowires possess a poor electrochemical response to HCHO oxidation, mainly due to the formation of a NiO surface layer. On the other hand, the modified Ni nanowires donated an electron to the HCHO oxidation reaction, resulting in high output-current densities, attributed to the thin Ni(OH)2/NiOOH layer, its amorphous state (TEM/SAED) and its small work function, due to electron doping from under the layered Ni. The modified Ni-nanowire-based electrodes had high sensitivity, reproducibility, selectivity and a low detection limit (0.8?µmol?/L). The developed HCHO Ni-nanowire-based electrodes’ characteristics surpass other Ni-based nanostructured electrodes and have limits of detection comparable to those achieved with noble metals.
COBISS.SI-ID: 32309543
In present work, we report on the enhanced electrocatalytic activity of formaldehyde oxidation in alkaline media for modified Ni nanowires (NWs)-based electrodes. Electrochemically deposited Ni NWs composed of metallic Ni and surface NiO were modified in KOH via cyclic voltammetry using different scan rates (10, 200 and 400 mV/s) in order to transform an inactive NiO to the surface-catalytic-active structurally disordered ß-NiOOH/ß-Ni(OH)2. Various characterisations (XRD and FT-IR) and calculations based on the electric charge were performed to understand the surface transformations which were found to be scan-rate dependant. The cyclic voltammetry results and kinetic parameters (Tafel plot) of formaldehyde oxidation revealed the superior electrocatalytic activity of the Ni-NW-electrode modified at 200 mV /s. The enhanced electrocatalytic performance, i.e., decreased onset overpotential by 400 mV when compared to Ni-based electrocatalysts, of this electrode was attributed to the thickness of structurally disordered the Ni–NiOOH/Ni(OH)2 and composite layered structure that enables the electron injection to reduce the NiOOH work function and thus promote the catalysis of formaldehyde oxidation. The proposed technique provides advances with a novel synthesis strategy for the preparation of highly active, structurally disordered ß-Ni(OH)2/ß-NiOOH redox systems on the surface of Ni-based nanostructured electrocatalysts for HCHO oxidation.
COBISS.SI-ID: 31863811
The main challenge with electrocatalysis is finding low-cost electrocatalysts that can work efficiently to oxidize the HCHO. Here, we propose a mechanism for the voltammetric formation of a highly active, structurally disordered ß-Ni(OH)2/ß-NiOOH redox pair on the surface of electrodeposited Ni thin films to achieve an extraordinary catalytic performance with respect to HCHO oxidation in alkaline media. We report electrochemical, XRD and FT-IR measurements on as-deposited and voltammetrically treated (i.e., KOH-modified) Ni thin films, and calculations based on the electrical charge to investigate the changes in the surface composition, crystal structure and related HCHO oxidation activity. We found that the KOH-modification process plays a crucial role in the formation of surface highly active, disordered ß-Ni(OH)2/ß-NiOOH. The KOH-modified Ni film with the largest amount of the structurally disordered ß-Ni(OH)2/ß-NiOOH resulted in improved catalytic performance, i.e., an onset overpotential reduced by 400 mV and a catalytic rate increased by 69 mV/dec. The presented technique has a wide range of applications and provides advances with a novel design idea and a new synthesis strategy for the preparation of highly active, structurally disordered Ni(OH)2/NiOOH redox systems on the surface of Ni thin films and other Ni-based nanostructured electrocatalysts for HCHO oxidation.
COBISS.SI-ID: 28465667
Using disposable screen-printed electrodes is a convenient way of monitoring environmental pollution, production process control etc. Usually, commercially available screen-printed electrodes are used, but more and more studies are being carried out in the field of printing electrodes on thinner, low-cost and versatile substrates, including paper. In the present research, the comparison of screen-printed electrodes printed on different paper-based materials is presented. Two unique and innovative invasive plant-based papers made from (1) Japanese knotweed, (2) Canadian and Giant goldenrod and (3) commercially available cardboard were used as a printing material for the electrodes. The selected paper substrates were characterized, and screen-printed electrodes were printed. The influence of substrates’ properties and pre or post-treatment of the screen-printed electrodes on the electrochemical behavior is thoroughly analyzed. The results indicate that the printing substrate (roughness) had the most significant influence on the cyclic voltammetry response. Comparing pre- and post-treatment of screen-printed electrodes, it was shown that grinding influenced the electrochemical activity significantly, while corona discharge does not have as significant influence. Besides, it was shown that the invasive plant-based papers are viable alternatives to commercially available papers and can be used as low-cost and eco-friendly alternatives for disposable screen-printed electrodes.
COBISS.SI-ID: 457408
The use of screen-printed electrodes in different monitoring applications, e.g., polluted water, biotechnology, agriculture, industrial process control, and other applications, are continuously being developed. New cheap and open-source potentiostats have been recently emerging, in addition to the commercial and proprietary solutions on the market. In this study, pPaper-based, screen-printed electrodes were utilised as an alternative solution for ceramic-based electrodes and were tested with two potentiostats (proprietary and low-cost open-source running on wireless 64 bit Linux system installed on Raspberry Pi 3+). Unique paper substrates made from invasive plant papers and one commercial were used for screen electrode printing. Ink layer thicknesses variations and mechanical grinding were applied, and cyclic voltammetry measurements were conducted. The results indicated that the cyclic voltammetry measurements' variation was two-folded, where potentiostats showed differences in their sensibility and signal values, and paper surface and structure also contributed to differences. Simultaneously, the additional processing steps, e.g., mechanical grinding, introduced additional measurement variations and differences in the measurement process.
COBISS.SI-ID: 59881731