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This study presents a novel method for synthesizing hierarchical porous zinc oxide (ZnO) nanostructures by thermally decomposing green-synthesized hydrozincite. The hydrozincite was prepared at room temperature using zinc acetate dihydrate and calcium carbonate (CaCO 3) in cellulose printing papers as the precipitating agent. The resulting ZnO particles exhibit a distinctive flower-like morphology, consisting of porous nanosheets composed of interconnected nanoparticles. The average crystallite size of the hierarchically structured zinc oxide nanoparticles, as determined via X-ray diffraction Rietveld refinement method, was found to be 18.8 nm when calcined at 500 °C. However, with increasing calcination temperature to 600, 700, and 800 °C, the average crystallite size also increased to 24.3, 30.4, and 47.2 nm, respectively. The ZnO synthesized at temperatures of 500 °C, 600 °C, and 700 °C exhibits higher electrocatalytic activity toward the hydrogen evolution reaction (HER) compared to both the ZnO synthesized at 800 °C and commercial ZnO. This enhanced performance can be primarily attributed to the nanosized ZnO particles, which provide a substantial surface area, high accessibility of active sites, and fast charge transfer kinetics. In terms of photocatalytic activity, all the samples show HER improvement under the UV light irradiation, attributed to the generation of photoexcited charge carriers. The ZnO synthesized at 800 °C and the commercial ZnO exhibit greater enhancements in photocatalytic activity compared to the other samples. This implies that larger solid particles with fewer nanopores result in a greater exposed surface area for UV-light absorption. The hierarchically structured ZnO nanoparticles demonstrate promising electrocatalytic and photocatalytic activities, as well as stability, opening up potential applications in various fields, including energy conversion and environmental remediation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Novel self-heating hydrogen sensor fabricated from zinc oxides nanorods on indium tin oxides. • Possess dual gas sensing capability based on resistance and temperature change. • Detection limit as low as 10 ppm in air. • Facile operation with mechanically-loaded contact electrodes. Abstract A novel self-heating hydrogen gas sensor based on zinc oxide nanorods coated on indium tin oxide was fabricated. This sensor utilizes Joule heating effect of indium tin oxide to generate heat, while ZnO acts as a variable resistor to regulate the amount of electric current that passes through indium tin oxide layer upon exposure to oxygen and hydrogen gas. The gas sensor was capable of detecting very low concentration of H 2 in air. Hence, for the first time, a new way of gas detection based on sensor temperature variation as the sensing mode was demonstrated. [ABSTRACT FROM AUTHOR]

In this work, high-performance non-platinum group metal (non-PGM) electrocatalysts for oxygen reduction reaction (ORR) are synthesized from graphene oxide-supported cobalt oxyhydroxide nanoparticles via a one-pot gamma radiolysis method. Investigations are conducted into how cobalt precursor concentration and the amount of gamma radiation affect the electrocatalysts' ability to perform oxygen reduction reactions as well as their physicochemical characteristics. Results show that the electrocatalyst prepared with the 0.1 M cobalt precursor and gamma radiation dose of 25 kGy has an advantage over the other samples in displaying good oxygen reduction activity. The characterization results of the synthesized electrocatalyst obtained through field-emission scanning electron microscopy–energy dispersive spectroscopy and X-ray diffraction combined with Rietveld refinement confirm the presence of nanosized cobalt oxyhydroxide particles that are evenly distributed on the surface of graphene oxide. ORR results show that the electrocatalyst has an onset potential of 0.90 V (vs. the reversible hydrogen electrode or RHE), a half-wave potential of 0.75 V (vs. RHE), a low peroxide yield of 7.08%, and an electron transfer number of 3.86, indicating a four-electron transfer path-way in the ORR process. This work provides an alternative facile means to mass-produce competitive non-PGM ORR electrocatalysts for fuel cell applications. • Novel gamma radiolysis-synthesized GO-supported CoOOH. • Strategies to optimize ORR performance via gamma irradiation dosage and cobalt precursor concentration. • Facile and scalable technique to produce competitive non-platinum group metal (non-PGM) ORR electrocatalysts. [ABSTRACT FROM AUTHOR]

• Humidity sensing characteristics of graphite pencil marks drawn on paper as sensing material were demonstrated. • Ethanol-treated sensors have better humidity sensitivities. • Intrinsic resistances of the sensors are directly proportional to their humidity sensitivity. • The humidity sensing characteristics of the pencil graphite were gauged with other forms of carbon materials. [Display omitted] In this study, we have demonstrated the humidity sensitivity of graphite pencil marks sensing material drawn on paper. The fabricated sensing devices (sensors) were characterized for their humidity sensitivity by measuring the resistance changes across the pencil marks. In order to improve the humidity sensitivity of the sensing material, ethanol chemical treatment was applied on the pencil marks to increase their surface hydrophilicity. Sensors with different levels of intrinsic resistances were also prepared and tested. Results showed that the ethanol-treated sensors have better humidity sensitivities and the intrinsic resistances of the sensors were directly proportional to their humidity sensitivity. To evaluate this carbon-based sensing material, the humidity sensing characteristics of the pencil graphite were gauged with other forms of carbon materials that have been reported in previous studies, such as carbon quantum dots film, carbon nanoparticles, carbon nanotubes, graphene oxide and graphene. [ABSTRACT FROM AUTHOR]

Replacing petroleum oil with renewable sources from natural oil in producing polymer coating is being widely attracting many researchers and inventors. In this study, palm oil-based urethane acrylate (POBUA) coating was developed as a protective coating for mild steel by using the ultraviolet irradiation technique. The POBUA was synthesized by reacting acrylated palm oil and isocyanate via in situ intercalative polymerizations with the presence of hydroxyethyl acrylate and 4 methoxy phenol (4mph). Different loadings of graphite particles (0.1 wt%, 0.5 wt% and 0.8 wt%) were introduced into the POBUA with the presence of Irgacure 184 as the photoinitiator. The formulated coating resin was applied on the mild steel substrates and the overall performances were investigated using Fourier transform infrared spectroscopy, contact angle measurements, X-Ray Diffraction, thermogravimetric analysis, electrochemical impedance spectroscopy, and Field Emission Scanning Electron Microscopy. Meanwhile, Gel content extraction and Pendulum Hardness were done on the cured film to investigate the performance of the polymerized coating polymer. The obtained results exposed good distribution of graphite particles in the POBUA polymeric matrix will influence the overall performance of the POBUA coatings at POBUA + 0.5 wt% graphite. Infrared spectrum demonstrated the formation of the crosslinked network was not disrupted with the addition of graphite particles, while increment of crystallinity index and hardness observed. Meanwhile TAFEL polarization elucidate the present of graphite particles reduced the curable POBUA coating corrosion current density from 102.6 × 10−6 to 27.3 × 10−12 Acm−2 with decreasing of mild steel corrosion rate per year from 31.24mpy to 125.1 × 10−6 mpy. However, morphology showed that the addition of high graphite content (0.8 wt%) increased the tendency to particles agglomeration. Nevertheless, the results obtained showed that the presence of graphite particles in POBUA is beneficial in improving the strength of the coating against surface degradation and corrosion. This research demonstrates that POBUA/Graphite curable coating has a good potential application in mild steel protection. • Anticorrosion study for palm oil-based urethane acrylate enhanced by graphite was carried out. • Graphite particles influences the corrosion behavior as shown in Tafel plot. • The strength of the coating against corrosion was enhanced with the presence of graphite. • Graphite particles enhanced charge transfer resistance R ct of POBUA. • The POBUA R ct increased from 0.92 × 106 Ω up to 9.253 × 106 Ω. [ABSTRACT FROM AUTHOR]