Search

The development of highly active and stable acidic water oxidation electrocatalysts is of great significant for promoting the industrial application of proton exchange membrane electrolyzers. Ru-based catalysts have broad application prospects in acidic water oxidation, but their limitations in stability and activity hinder their further application. Herein, a nitrogen-doped carbon (NC) coated porous Ru/RuO2 heterojunctional hollow sphere (Ru/RuO2/NC) is designed as high-active and stable bifunctional electrocatalyst for acidic oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). In synthesis, the key is to use mesoporous polydopamine spheres as a template for forming hollow spheres, a source of NC coating and a reducing agent for forming Ru/RuO2 heterojunction. The Ru/RuO2 heterojunction adjusts the electronic structure of Ru active sites, optimizing the adsorption of intermediate species. Furthermore, the NC coating and the interaction between NC and Ru/RuO2 effectively prevent Ru from over-oxidation and dissolution. The porous hollow structure provides more exposed active sites and promotes mass transfer. Impressively, Ru/RuO2/NC exhibits outstanding OER and HER performance with low overpotentials of 211 and 32 mV at 10 mA·cm−2, respectively, and shows excellent stability. The acid water splitting electrolyzer, based on the bifunctional Ru/RuO2/NC, requires low cell voltages of 1.46 and 1.76 V at 10 and 100 mA·cm−2, respectively, with good stability for over 100 h operation, surpassing Pt/C∥RuO2 and most of the reported catalysts. [ABSTRACT FROM AUTHOR]

The design of two-dimensional (2D) CoN-based thin sheets is promising in the catalytic field. The typical synthesis based on the thermal treatment of the hydroxide sheets results in enhanced particle size and thick sheets. Here, we show a novel route based on in situ conversion of Co–CoN nanowires into ultra-thin sheets for effective catalytic hydrogenation. The Co–CoN nanowires were first prepared by the pyrolysis of 1D cobalt-nitrilotriacetic acid nanowires (Co-NTA NWs) and used for the catalytic hydrogenation of p-nitrophenol (P-NP) into p-aminophenol (P-AP) in the presence of NaBH4. Unexpectedly, during the second catalytic run, the catalytic activity showed an obvious enhancement with a conversion rate of 99% within 60 seconds, which was better than the time of 90 seconds in the first use. The improved activity should be related to the formation of thin nanosheets. A further study of the catalyst showed the in situ formation of Co–CoN thin sheets on nanowires during the catalytic reaction. The sequential conversion from nanowires to nanosheets–nanowires and then to the final thin sheets was demonstrated. The presence of the NaBH4 and P-NP is key to promote the conversion. The performance shows no obvious change after continuous catalysis for seven cycles. The in situ conversion synthesis will be instructive for the design of other functional catalysts through an induced conversion process. [ABSTRACT FROM AUTHOR]

Developing stable and highly active electrocatalysts for the oxygen evolution reaction (OER) in acidic media holds significant importance for proton-exchange membrane water electrolysis. Here, we report a carbon-protected, low Ru-doped cobalt oxide nanosheet array electrode (C–Ru–Co3O4) for acid OER. The doping of Ru adjusts the electronic structure, optimizing the adsorption of reaction intermediates. Additionally, amorphous carbon, derived from polydopamine, effectively inhibits the overoxidation of Ru–Co3O4. Furthermore, the sheetlike structure and strong interplay between the catalyst and support promote mass and charge transfer while extending the long-term durability. Compared to Co3O4 and commercial RuO2 catalysts, C–Ru–Co3O4 catalyst exhibits enhanced OER performance and stability. The optimized catalyst shows an overpotential of 252 mV at 10 mA cm–2 and can operate continuously in acidic media for more than 30 h, while the activity of commercial RuO2 sharply decreases within 1 h. Notably, C–Ru–Co3O4 also exhibits good hydrogen evolution reaction (HER) activity, with an overpotential of 125 mV at 10 mA cm–2. Furthermore, the acid water splitting electrolyzer, based on bifunctional C–Ru–Co3O4, can be effectively driven by a solar panel, revealing its potential for converting solar energy into clean chemical energy. [ABSTRACT FROM AUTHOR]

Carbon nitride (C3N4) has gained considerable attention and has been regarded as an ideal candidate for photocatalytic hydrogen evolution. However, its photocatalytic efficiency is still unsatisfactory due to the rapid recombination rate of photo-generated carriers and restricted surface area with few active sites. Herein, we successfully synthesized a single-atom Pt cocatalyst-loaded photocatalyst by utilizing the anchoring effect of carbon dots (CDs) on C3N4. The introduction of CDs onto the porous C3N4 matrix can greatly enhance the specific surface area of C3N4 to provide more surface-active sites, increase light absorption capabilities, as well as improve the charge separation efficiency. Notably, the functional groups of CDs can efficiently anchor the single-atom Pt, thus improving the atomic utilization efficiency of Pt cocatalysts. A strong interaction is formed via the connection of Pt-N bonds, which enhances the efficiency of photogenerated electron separation. This unique structure remarkably improves its H2 evolution performance under visible light irradiation with a rate of 15.09 mmol h−1 g−1. This work provides a new approach to constructing efficient photocatalysts by using CDs for sustainable hydrogen generation, offering a practical approach to utilizing solar energy for clean fuel production. [ABSTRACT FROM AUTHOR]