Single-atom catalysts (SACs) have emerged as one of the most promising alternatives to noble metal-based catalysts for highly efficient oxygen reduction reaction (ORR). While SACs can offer notable benefits in terms of lowering overall catalyst cost, there is still room for improvement regarding catalyst activity. To this end, we designed and successfully fabricated an ORR electrocatalyst in which atomic clusters are embedded in an atomically dispersed Fe–N–C matrix (FeAC@FeSA–N–C), as shown by comprehensive measurements using aberration-corrected scanning transmission electron microscopy (AC-STEM) and X-ray absorption spectroscopy (XAS). The half-wave potential of FeAC@FeSA–N–C is 0.912 V (versus reversible hydrogen electrode (RHE)), exceeding that of commercial Pt/C (0.897 V), FeSA–N–C (0.844 V), as well as the half-wave potentials of most reported non-platinum-group metal catalysts. The ORR activity of the designed catalyst stems from single-atom active centers but is markedly enhanced by the presence of Fe nanoclusters, as confirmed by both experimental measurements and theoretical calculations.

One of the key challenges that hinders broad commercialization of proton exchange membrane fuel cells is the high cost and inadequate performance of the catalysts for oxygen reduction reaction (ORR)....

Reversible protonic ceramic electrochemical cells (R-PCECs) are a promising option for efficient and low-cost generation of electricity and hydrogen. Commercialization of R-PCECs, however, hinges on the development of highly active and robust air electrodes. Here, we report an air electrode consisting of PrBa 0.8 Ca 0.2 Co 2 O 5+δ and in situ exsolved BaCoO 3−δ nanoparticles (PBCC−BCO) that shows minimal polarization resistance (∼0.24 Ω cm 2 at 600 °C) and high stability when exposed to humidified air with 3−50% H 2 O. An R-PCEC utilizing PBCC-BCO demonstrates remarkable performances at 600 °C: achieving a peak power density of 1.06 W cm −2 in the fuel cell mode and a current density of 1.51 A cm −2 at 1.3 V in an electrolysis mode. More importantly, the R-PCECs demonstrate an exceptionally high durability over 1833 h of continuous operation in the electrolysis mode. This work offers an efficient approach to design of high-performance and durable electrodes for R-PCECs.

The micrometer-sized H-Nb2O5 could achieve fast lithium-ion storage by engineering its planar defects.

Reversible solid oxide cells based on ceramic proton conductors have potential to be the most efficient system for large‐scale energy storage. The performance and long‐term durability of these systems, however, are often limited by the ionic conductivity or stability of the proton‐conducting electrolyte. Here new family of solid oxide electrolytes, BaHfxCe0.8−xY0.1Yb0.1O3−δ (BHCYYb), which demonstrate a superior ionic conductivity to stability trade‐off than the state‐of‐the‐art proton conductors, BaZrxCe0.8−xY0.1Yb0.1O3−δ (BZCYYb), at similar Zr/Hf concentrations, as confirmed by thermogravimetric analysis, Raman, and X‐ray diffraction analysis of samples over 500 h of testing are reported. The increase in performance is revealed through thermodynamic arguments and first‐principle calculations. In addition, lab scale full cells are fabricated, demonstrating high peak power densities of 1.1, 1.4, and 1.6 W cm−2 at 600, 650, and 700 °C, respectively. Round‐trip efficiencies for steam electrolysis at 1 A cm−2 are 78%, 72%, and 62% at 700, 650, and 600 °C, respectively. Finally, CO2H2O electrolysis is carried out for over 700 h with no degradation.

Cost-effective production of ammonia via electrochemical nitrogen reduction reaction (NRR) hinges on N 2 electrolysis at high current densities with suitable selectivity and activity. Here, we report our findings in electrochemical NRR for ammonia synthesis using porous bimetallic Pd−Ag nanocatalysts in both gas-phase and liquid-phase electrochemical cells at current densities above 1 mA cm −2 under ambient conditions. While the gas-phase cell has lower Ohmic losses and higher energy efficiency, the liquidphase cell achieved higher selectivity and Faradaic efficiency, attributed to the presence of concentrated N 2 molecules dissolved in an aqueous electrolyte and the hydration effects. The liquid cell demonstrated notable performance for electrocatalytic NRR, achieving an NH 3 production rate of 45.6 ± 3.7 μg cm −2 h −1 at a cell voltage of −0.6 V (vs RHE) and current density of 1.1 mA cm −2 , corresponding to a Faradaic efficiency of ∼19.6% and an energy efficiency of ∼9.9%. Similarly, the gas-phase cell achieved a NH 3 yield rate of 19.4 ± 2.1 μg cm −2 h −1 at −0.07 V (vs RHE) and 1.15 mA cm −2 with a Faradaic efficiency of 7.9% and an energy efficiency of 27.1%. Further, operando surface-enhanced Raman spectroscopy and density functional theory (DFT) are used to identify intermediate species relevant to the NRR at the electrode− electrolyte interfaces to provide insights into the NRR mechanism on Pd−Ag nanoparticles. This work highlights the importance of design and optimization of cell configuration in addition to the modification of the catalyst to achieve high-performance N 2 electrolysis for ammonia synthesis.

Intermediate temperature solid oxide fuel cells (IT‐SOFCs) are cost‐effective and efficient energy conversion systems. The sluggish oxygen reduction reaction (ORR) and the degradation of cathodes are critical challenges to the commercialization of IT‐SOFCs. Here, a highly efficient multiphase (MP) catalyst coating, consisting of Ba1−xCo0.7Fe0.2Nb0.1O3−δ (BCFN) and BaCO3, to enhance the ORR activity and durability of the state‐of‐the‐art lanthanum strontium cobalt ferrite (La0.6Sr0.4Co0.2Fe0.8O3−δ, LSCF) cathode is reported. The conformal MP catalyst‐coated LSCF cathode shows a polarization resistance (Rp) of 0.048 Ω cm2 at 650 °C, about one order of magnitude smaller than that of the bare LSCF. In an accelerated Cr‐poisoning test, the degradation rate of the catalyst‐coated LSCF electrode is 10−3 Ω cm2 h−1 (0.59% h−1) over 200 h, only one fifth of the degradation rate of the bare LSCF electrode at 750 °C. In addition, anode‐supported single cells with the MP catalyst‐coated LSCF cathode show a dramatically enhanced peak power density (1.4 W cm−2 vs 0.67 W cm−2 at 750 °C) and increased durability against Cr and H2O. Both experimental results and density functional theory‐based calculations indicate that the BCFN phase improves the ORR activity while the BaCO3 phase enhances the stability of the LSCF cathode.

No abstract