Search Results (4)

Amorphous cobalt-phosphorous (CoP) coatings are a candidate to replace hard chromium and other traditional coatings. Here, electrodeposition of both amorphous and crystalline CoP coatings was performed at room temperature and in an air environment. The bath composition and deposition conditions were optimized to offer a low cost, low maintenance, and safe process. The effects of various deposition variables such as solution composition, pH, duration, and mixing parameters were studied, and the reproducibility of the process was demonstrated. Selected coatings were then thoroughly characterized by a variety of techniques. The best amorphous/nanocrystalline coating contained ca. 6.4 wt.% P after 1.2 h of deposition, and 7.2 wt.% P after 4 h of deposition. The best crystalline coating contained ca. 2.7 wt.% P after 1.2 h of deposition and between 2.3 and 5.5 wt.% P after 4 h of deposition. The amorphous coating had excellent mechanical properties: a high hardness (7.8 ± 0.7 GPa), high Young’s modulus (153 ± 9 GPa), and surprisingly low coefficient of dry friction (between 0.11 ± 0.02 and 0.17 ± 0.01). The coating could not be scraped from the substrate using a diamond scalpel blade. In a standard adhesion test, the sample failed neither cohesively within the coating nor adhesively between the coating and the substrate. In the as-deposited conditions, the structure was uniform, nanocrystalline, or had nanocrystals embedded in an amorphous matrix. The crystallization temperature of the amorphous alloy was 284 °C, and the phase transformation occurred only between 300 and 400 °C. The coatings developed and comprehensively characterized herein may be considered for aerospace, magnetic storage, fuel cells, water splitting, and other applications. Full article

Recently, ascorbic acid (AA) has been studied as an environment-friendly fuel for energy conversion devices. This review article has deliberated an overview of ascorbic acid electrooxidation and diverse ion exchange types of AA-based fuel cells for the first time. Metal and carbon-based catalysts generated remarkable energy from environment-friendly AA fuel. The possibility of using AA in a direct liquid fuel cell (DLFC) without emitting any hazardous pollutants is discussed. AA fuel cells have been reviewed based on carbon nanomaterials, alloys/bimetallic nanoparticles, and precious and nonprecious metal nanoparticles. Finally, the obstacles and opportunities for using AA-based fuel cells in practical applications have also been incorporated. Full article

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are key reactions in energy-converting systems, such as fuel cells (FCs) and water-splitting (WS) devices. However, the current use of expensive Pt-based electrocatalysts for ORR and IrO₂ and RuO₂ for OER is still a major drawback for the economic viability of these clean energy technologies. Thus, there is an incessant search for low-cost and efficient electrocatalysts (ECs). Hence, herein, we report the preparation, characterization (Raman, XPS, and SEM), and application of four composites based on doped-carbon materials (CM) and cobalt phosphotungstate (MWCNT_N8_Co4, GF_N8_Co4, GF_ND8_Co4, and GF_NS8_Co4) as ORR and OER electrocatalysts in alkaline medium (pH = 13). Structural characterization confirmed the successful carbon materials doping with N and/or N, S, and the incorporation of the cobalt phosphotungstate. Overall, all composites showed good ORR performance with onset potentials ranging from 0.83 to 0.85 V vs. RHE, excellent tolerance to methanol crossover with current retentions between 88 and 90%, and good stability after 20,000 s at E = 0.55 V vs. RHE (73% to 82% of initial current). In addition, the number of electrons transferred per O₂ molecule was close to four, suggesting selectivity to the direct process. Moreover, these composites also presented excellent OER performance with GF_N8_Co4 showing an overpotential of 0.34 V vs. RHE (for j = 10 mA cm⁻²) and j_max close to 70 mA cm⁻². More importantly, this electrocatalyst outperformed state-of-the-art IrO₂ electrocatalyst. Thus, this work represents a step forward toward bifunctional electrocatalysts using less expensive materials. Full article

The idea of a “Hydrogen Economy” is that carbon containing fuels should be replaced by hydrogen, thus eliminating air pollution and growth of CO₂ in the atmosphere. However, storage of a gas, its transport and reconversion to electricity doubles the cost of H₂ from the electrolyzer. Methanol made with CO₂ from the atmosphere is a zero carbon fuel created from inexhaustible components from the atmosphere. Extensive work on the splitting of water by bacteria shows that if wastes are used as the origin of feed for certain bacteria, the cost for hydrogen becomes lower than any yet known. The first creation of hydrogen and electricity from light was carried out in 1976 by Ohashi et al. at Flinders University in Australia. Improvements in knowledge of the structure of the semiconductor-solution system used in a solar breakdown of water has led to the discovery of surface states which take part in giving rise to hydrogen (Khan). Photoelectrocatalysis made a ten times increase in the efficiency of the photo production of hydrogen from water. The use of two electrode cells; p and n semiconductors respectively, was first introduced by Uosaki in 1978. Most photoanodes decompose during the photoelectrolysis. To avoid this, it has been necessary to create a transparent shield between the semiconductor and its electronic properties and the solution. In this way, 8.5% at 25 °C and 9.5% at 50 °C has been reached in the photo dissociation of water (GaP and InAs) by Kainthla and Barbara Zeleney in 1989. A large consortium has been funded by the US government at the California Institute of Technology under the direction of Nathan Lewis. The decomposition of water by light is the main aim of this group. Whether light will be the origin of the post fossil fuel supply of energy may be questionable, but the maximum program in this direction is likely to come from Cal. Tech. Full article