RESUMEN
The discovery of efficient and stable electrocatalysts for oxygen evolution reaction (OER) in acid is vital for the commercialization of the proton-exchange membrane water electrolyzer. In this work, we demonstrate that short-range Ru atom arrays with near-ideal Ru-Ru interatomic distances and a unique Ru-O hybridization state can trigger direct O*-O* radical coupling to form an intermediate O*-O*-Ru configuration during acidic OER without generating OOH* species. Further, the Ru atom arrays suppress the participation of lattice oxygen in the OER and the dissolution of active Ru. Benefiting from these advantages, the as-designed Ru array-Co3O4 electrocatalyst breaks the activity/stability trade-off that plagues RuO2-based electrocatalysts, delivering an excellent OER overpotential of only 160 mV at 10 mA cm-2 in 0.5 M H2SO4 and outstanding durability during 1500 h operation, representing one of the best acid-stable OER electrocatalysts reported to date. 18O-labeled operando spectroscopic measurements together with theoretical investigations revealed that the short-range Ru atom arrays switched on an oxide path mechanism (OPM) during the OER. Our work not only guides the design of improved acidic OER catalysts but also encourages the pursuit of short-range metal atom array-based electrocatalysts for other electrocatalytic reactions.
RESUMEN
An efficient chemical synthesis route, with an aim of reaching an ultrahigh nitrogen (N)-doping level in carbon materials can provide a platform where the type and amount of N dopant can be tuned over a wide range. We propose a C-S-C linkage-triggered confined-pyrolysis strategy for the high-efficiency inâ situ N-doping into carbon matrix and an ultrahigh doping level up to 13.5â at %, which is close to the theoretical upper limit (15.2â at %) is realized at a high carbonization temperature of 1000 °C. The pyridinic N is dominant with a maximum percent of 48.7 %. By using I3 - reduction as an example, the resultant NCM-5 exhibits the best activity with a power conversion efficiency of 8.77 %. A pyridinic N site-dependent activity is demonstrated in which the amount of active sites increases with the increase of pyridinic N, and the carbon atom adjacent to electron-withdrawing pyridinic N at the armchair edge acts as the most favorable site for the adsorption of I2 .
RESUMEN
The methodology of metal-involved preparation for carbon materials is favored by researchers and has attracted tremendous attention. Decoupling this process and the underlying mechanism in detail are highly required. Herein, the intrinsic mechanism of carbon fixation in graphitic carbon nitride (g-C3 N4 ) via the magnesium-involved carbonization process is reported and clarified. Magnesium can induce the displacement reaction with the small carbon nitride molecule generated by the pyrolysis of g-C3 N4 , thus efficiently fixing the carbon onto the in situ template of Mg3 N2 product to avoid the direct volatilization. As a result, the N-doped carbon nanosheet frameworks with interconnected porous structure and suitable N content are constructed by reconstruction of carbon and nitrogen species, which exhibit a comparable photoelectric conversion efficiency (8.59%) and electrocatalytic performances to that of Pt (8.40%) for dye-sensitized solar cells.
RESUMEN
The Pd/C catalysts are widely used in synthesis of fine chemicals in industry, but their production suffers from a complicated two-step process involving impregnation and reduction, and requires large amounts of solvents and reductant, which would lead to a series of issues such as time consumption, resource waste and environmental pollution. Herein, ultra-small Pd nanoparticles uniformly anchored on carbon nanotubes (Pd/CNTs) were synthesized by using a one-pot and low-temperature reduction strategy. The present process/technology is very sensitive to and controlled by the supports and solvents, and the carbon support and acetic acid synergistically play crucial and decisive roles in the fast production of Pd/C catalysts. Also, the used solvents can be recycled and reutilized, which meets the requirements of sustainable chemistry and green economy. When the as-obtained Pd/CNTs catalyst was used to catalyze the oxidation of benzyl alcohol to benzaldehyde, it achieved a conversion efficiency as high as 99.3 % and a high selectivity up to >99.9 %. The simple, scalable and environmentally friendly strategy can be extended to anchor Pd nanoparticles on various carbon substrates, which sheds a new light on the synthesis of Pd/C catalysts.
RESUMEN
The discovery of low-cost and high-performance bifunctional oxygen electrocatalysts is vital to the future commercialization of rechargeable zinc-air batteries (ZABs). Herein, a Fe single atom seed-mediated strategy is reported for the fabrication of Fe3 C species closely surrounded by FeN4 C active sites with strong electronic interactions built between them and more importantly, creating optimized coordination environment, via subtly adjusting their ratio, for favorable adsorption energies of oxygen intermediates formed during oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Concretely, the voltage difference (ΔE) between the ORR half-wave and OER potential at a current density of 10 mA cm-2 for the compositionally-optimized FeNC/Fe3 C-op electrocatalyst is only 0.668 V, endowing itself one of the best bifunctional OER/ORR benchmarks. As a demo, ZABs assembled with FeNC/Fe3 C-op as the air cathode deliver a remarkable specific capacity (818.1 mAh gZn -1 ) and a power density (1013.9 mWh gZn -1 ), along with excellent long-term durability (>450 h). This work extends the methodology to modulate the activity of FeN4 C atomic site, undoubtedly inspiring wide explorations on the precise design of bifunctional oxygen electrocatalysts.