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Wyświetlanie 1-10 z 93
Tytuł:
Maximising the potential of reactive carbon support with cobalt active phase for the oxygen evolution reaction
Autorzy:
Darvishzad, Termeh
Stelmachowski, Paweł
Opis:
A growing interest in novel noble metal-free electrocatalysts is fuelled by the pressing need to overcome the drastic demand for sustainable energy sources. To this end, the oxygen evolution reaction (OER) utilising transition metal oxide–carbon composites in alkaline media is considered a robust technology. In many such systems, carbon is used as a conductive additive or support, and the interactions between carbon support materials and the active phase affect the efficiency of the electrocatalyst. Cobalt forms some of the most active and stable electrocatalysts for OER. In carbon-supported systems, the dispersion of the cobalt phase on the carbon surface is a key factor in influencing the catalyst activity in water-splitting reactions. In this study, a low-temperature plasma treatment is used to boost the efficiency of the cobalt active phase by functionalising the carbon support with various oxygen groups. We used a simple deposition–precipitation method to obtain cobalt hydroxide active phase over graphene nanoparticles. The activation of graphene nanoparticles with oxygen plasma allowed us to obtain a catalyst that showed only 317 mV@10 $mA·cm^{−2}$. More importantly, in the series of plasma-activated samples, the OER activity was very high in a range of cobalt phase loadings, yielding a material with 2.4 wt.% of cobalt and an overpotential of only 327 mV@10 $mA·cm^{−2}$. The results indicate that plasma activation of GNP support maximises the usage of the transition metal active phase, which allows for an improvement in area-normalised and a dramatic improvement in the mass-normalised OER electrocatalytic activity.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
Exploring the potential of biochars for boosting electrocatalytic oxygen evolution reaction
Autorzy:
Stelmachowski, Paweł
Lofek, Magdalena
Wojtasik, Michał
Markowski, Jaroslaw
Opis:
The world's growing energy demand and the necessity of protecting the environment motivate researchers and industry alike to look for an ecological alternative to fossil fuels as energy sources and carriers, such as hydrogen. On the other hand, biomass waste can be used to obtain bio-oil for energy applications. Fast pyrolysis of biomass results in the highest bio-oil yields, but poor physicochemical properties characterise the produced biochar. This work aimed to develop a procedure to make an electrocatalyst of the oxygen evolution reaction (OER) to produce hydrogen based on biochar from fast pyrolysis of renewable raw materials (carbonised triticale straw, sunflower husk, pine sawdust, walnut shells, and sewage sludge) with a cobalt active phase. No additional chemical and thermal valorisation was applied to increase the graphitisation degree, porosity and specific surface area. However, simple and environmentally friendly air plasma was used as a non-destructive method to improve the surface properties of the biochar materials. The cobalt active phase was introduced by a deposition-precipitation method. The surface modification of carbon materials with plasma improves the electrocatalytic activity by changing the speciation of the biochars' surface oxygen groups. The activity of the obtained materials is very similar, irrespective of the different characteristics of the studied fast pyrolysis by-products, indicating that the developed materials can be obtained from various biochars. The OER overpotentials at $10 mA cm^{−2}$ for all the samples are below 385 mV. The most active material, based on plasma-treated triticale straw biochar $(C_{TS}-pl-Co)$, demonstrated the lowest overpotential of 358 mV, representing a slight improvement compared to its untreated counterpart (η = 363 mV). Furthermore, the $C_{TS}-pl-Co$ catalyst maintained stable operation for 6 h at a current density of $18 mA cm^{−2}$, in contrast to the reference cobalt spinel, which operated for only 3 h at a current density of $15 mA cm^{−2}$. These findings underscore the potential of plasma-functionalised waste-derived biochars as sustainable and effective catalysts for OER applications.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Wyświetlanie 1-10 z 93

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