The design of multiphase heterostructures presents a promising strategy for oxygen evolution reaction (OER) and serves as an effective approach to constructing efficient alkaline OER catalysts. In this paper, the OER catalyst with a NiFe-NS/NiMoO4 layered heterostructure was synthesized by reflux condensation and hydrothermal methods. The unique rock-like nanospheres can increase the specific surface area and provide more active sites. The formation of heterojunctions through the modification of NiFe nanospheres on NiMoO4 nanorods can induce changes in their electronic structure. Due to its inherent properties, NiFe-NS/NiMoO4 demonstrates higher performance than commercial RuO2 (which has an overpotential of 228 mV at a current density of 10 mA cm–2), with overpotentials of 196 and 294 mV at current densities of 10 and 100 mA cm–2, respectively. The stability of the sample was proved to be excellent during a 50 h stability test. Density functional theory (DFT) calculations also indicate that the improved efficiency of the OER can be attributed to controlling and adjusting of the electron structure through heterojunction formation as well as the collaborative impact resulting from NiFe and NiMoO4. The structure enables optimized adsorption of intermediates and facilitates the kinetics of OER, and provides an idea for the design of heterogeneous catalysts.
Tian Gan,Bin Sheng,Quanyu Zeng,Yuchen Li,Yujun Han,Wenya Zhen,Ping Li,Yongdan Li
A high-performance anode of a solid oxide fuel cell (SOFC) should possess excellent electrocatalytic activity, high oxygen-ion/electron conductivity, and sufficient operational stability, thus requiring a delicate tuning of both the bulk and surface properties of the electrode materials. Constructing heterostructures to obtain high electrocatalytic activity catalysts is an essential but challenging research direction. Herein, a novel composite anode constructed with multiphase nanoparticles is rationally designed and prepared using intelligent in situ reconstruction technique. The self-assembled La 0.9 Ce 0.1 Ni 0.7 Co 0.15 Fe 0.15 O 3-δ -Sm 0.2 Ce 0.8 O 2 (LCNCF-SDC) anode was in situ reconstructed under reducing atmosphere to form uniform NiCoFe/CeO 2 /La 2 O 3 multiphase heterostructures. As a result, the maximum power densities of a cell supported by 500 μm-thick Ce 0.8 Sm 0.2 O 2-δ -carbonate electrolyte layer with the LCNCF-SDC anode reach 1.34 and 1.56 W cm −2 at 700 °C, respectively for using H 2 and methanol as fuels. The synergy between multiphase nanoparticles contributes to the enhanced catalytic activity and stability. This anode demonstrates negligible degradation over 15 h in CH 3 OH, indicating a significantly enhanced coking resistance.
Here, in situ assembly in La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ and CoFe 2 O 4 composite (LSCFC) cathode was induced by Pr to form La 0.6 Sr 0.4 Co x Fe y O 3-δ /PrCoO 3 /Co 3 O 4 /PrO 2 (LSCFC-PI) multiphase heterostructures . The surface of LSCFC-PI forms uniform nanoparticles , and the unique core-shell structure prevents Sr segregation, thereby enhancing CO 2 tolerance and increasing oxygen reduction reaction (ORR) active sites. Furthermore, compared with LSCFC, LSCFC-PI increases the oxygen vacancy content of the cathode due to the existence of multiphase heterostructure, improves the ORR kinetics, and the conductivity is also greatly improved. The peak power density (PPD) of LSCFC-PI as a single-cell cathode at 700 ℃ reached 1.51 W cm −2 , which was 2.65 times higher than that of LSCFC's 0.57 W cm −2 , and in the long-term stability test at a constant voltage ∼0.8 V for 100 hours, showing excellent stability. In situ assembly of multiphase heterostructures is expected to become a new strategy for developing high-performance IT-SOFC cathodes.
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