Regulating the thickness of the carbon coating layer in iron/carbon heterostructures to enhance the catalytic performance for oxygen evolution reaction.

The exploration of high-performance electrocatalysts for the oxygen evolution reaction (OER) is crucial and urgent for the fast development of green and renewable hydrogen energy. Herein, an ultra-fast and energy-efficient preparation strategy (microwave-assisted rapid in-situ pyrolysis of organometallic compounds induced by carbon nanotube (CNT)) is developed to obtain iron/carbon (Fe/C) heterogeneous materials (Fe/Fe3C particles wrapped by carbon coating layer). The thickness of the carbon coating layer can be adjusted by changing the content and form of carbon in the metal sources during the fast preparation process. Fe/Fe3C-A@CNT using iron acetylacetonate as metal sources possesses unique Fe/C heterogeneous, small Fe/Fe3C particles encapsulated by the thin carbon coating layer (1.77 nm), and obtains the optimal electron penetration effect. The electron penetration effect derives from the redistribution of charge between the surface carbon coating layer and inner Fe/Fe3C nanoparticles efficiently improving both catalytic activity and stability. Therefore, Fe/Fe3C-A@CNT shows efficient OER catalytic activity, just needing a low overpotential of 292 mV to reach a current density of 10 mA cm-2, and long-lasting stability. More importantly, the unique control strategy for carbon thickness in this work provides more opportunity and perspective to prepare robust metal/carbon-based catalytic materials at the nanoscale.

Utilizing the cross-linked effect and reconstruction strategy of phytic acid to build Fe-Co-Ni trimetallic amorphous carbon-matrix compounds as efficient oxygen evolution catalyst.

Developing low-cost electrocatalysts with excellent activity is significant for accelerating the slow oxygen evolution reaction (OER). In this work, an effective electrocatalyst is prepared via the cross-linked effect and reconstruction strategy based on inexpensive transition metals (Fe, Co, and Ni) and phytic acid (PA). The feasibility of utilizing the cross-linked effect and reconstruction strategy is due to that PA molecules with strongly electronegative phosphoric acid groups possess a great deal of complexing sites, which can facilitate the formation of large cross-linked network by randomly complexing Fe, Co and Ni ions. And the carboatomic rings in PA molecules will reconstructed as carbon-matrix when PA molecules decompose. The above structural evolution of large cross-linked network and reconstructing process is rigorously analyzed through the characterization methods such as XPS. These analysis results indicate that FeCoNi-PA-300 possesses a high degree of amorphization, an abundant nanoporous structure, and a small nanoparticle size, resulting in a large electrochemically active area. Consequently, FeCoNi-PA-300 just needs low overpotentials of about 271 mV and 286 mV to obtain the current densities of 50 and 100 mA cm-2, respectively. Meaningfully, this synthetic method is a general strategy to meliorate the OER activity and electrical conductivity of other catalysts.

Ultrafast fabrication of robust electrocatalyst having Fe/Fe3C and CuNC for enhanced oxygen reduction reaction activity.

The search for ultrafast and simple methods to fabricate non-noble metal catalysts to boost electrocatalytic oxygen reduction reaction (ORR) is still ongoing. Herein, we demonstrate a one-step microwave-assisted heating method to prepare copper nitride/iron/iron carbide nanoparticle hybrids (CuNC/Fe/Fe3C/CNT). This ultrafast heating method induces plentiful carbon-wrapped metal and Fe3C nanoparticles that are attached to the surface of CNT and scattered nanosheets. The CuNC/Fe/Fe3C/CNT exhibit a half-wave potential (E1/2) of 0.886 V toward the ORR in alkaline solution, with 220 mV more positive E1/2 than that of CuNC/CNT and Fe/Fe3C/CNT respectively. The activity of as-prepared catalysts is discussed by investigating their structures and compositions and their relationship with the ORR performance. Detailed analysis results disclose that the high activity of the CuNC/Fe/Fe3C/CNT catalysts could be attributed to the interaction of CuNC and Fe/Fe3C species. To be specific, as the electron donor, Fe/Fe3C nanoparticles induce electron localization and promote the formation of Cu (δ + )-NC (0 < Î´ < 2), therefore leading to the improvement of the ORR performance. This work may offer an ultrafast way to construct efficient catalysts with enhanced ORR performance.