Calcium-mediated nitrogen reduction for electrochemical ammonia synthesis.
Ammonia (NH3) is a key commodity chemical for the agricultural, textile and pharmaceutical industries, but its production via the Haber-Bosch process is carbon-intensive and centralized. Alternatively, an electrochemical method could enable decentralized, ambient NH3 production that can be paired with renewable energy. The first verified electrochemical method for NH3 synthesis was a process mediated by lithium (Li) in organic electrolytes. So far, however, elements other than Li remain unexplored in this process for potential benefits in efficiency, reaction rates, device design, abundance and stability. In our demonstration of a Li-free system, we found that calcium can mediate the reduction of nitrogen for NH3 synthesis. We verified the calcium-mediated process using a rigorous protocol and achieved an NH3 Faradaic efficiency of 40±2% using calcium tetrakis(hexafluoroisopropyloxy)borate (Ca[B(hfip)4]2) as the electrolyte. Our results offer the possibility of using abundant materials for the electrochemical production of NH3, a critical chemical precursor and promising energy vector.
View details for DOI 10.1038/s41563-023-01702-1
View details for PubMedID 37884670
- Quantifying Influence of the Solid-Electrolyte Interphase in Ammonia Electrosynthesis ACS ENERGY LETTERS 2023
Development of a versatile electrochemical cell for in situ grazing-incidence X-ray diffraction during non-aqueous electrochemical nitrogen reduction.
Journal of synchrotron radiation
In situ techniques are essential to understanding the behavior of electrocatalysts under operating conditions. When employed, in situ synchrotron grazing-incidence X-ray diffraction (GI-XRD) can provide time-resolved structural information of materials formed at the electrode surface. In situ cells, however, often require epoxy resins to secure electrodes, do not enable electrolyte flow, or exhibit limited chemical compatibility, hindering the study of non-aqueous electrochemical systems. Here, a versatile electrochemical cell for air-free in situ synchrotron GI-XRD during non-aqueous Li-mediated electrochemical N2 reduction (Li-N2R) has been designed. This cell not only fulfills the stringent material requirements necessary to study this system but is also readily extendable to other electrochemical systems. Under conditions relevant to non-aqueous Li-N2R, the formation of Li metal, LiOH and Li2O as well as a peak consistent with the alpha-phase of Li3N was observed, thus demonstrating the functionality of this cell toward developing a mechanistic understanding of complicated electrochemical systems.
View details for DOI 10.1107/S1600577523006331
View details for PubMedID 37594864
Sol-Gel Barium Titanate Nanohole Array as a Nonlinear Metasurface and a Photonic Crystal
The quest of a nonlinear optical material that can be easily nanostructured over a large surface area is still ongoing. Here, we demonstrate a nanoimprinted nonlinear barium titanate 2D nanohole array that shows the optical properties of a 2D photonic crystal and a metasurface, depending on the direction of the optical axis. The challenge of nanostructuring the inert metal-oxide is resolved by direct soft nanoimprint lithography with sol-gel derived barium titanate enabling critical dimensions of 120 nm with aspect ratios of five. The nanohole array exhibits a photonic bandgap in the infrared range when probed along the slab axis, while lattice resonant states are observed in out-of-plane transmission configuration. The enhanced light-matter interaction from the resonant structure enables to increase in the second-harmonic generation in the near-ultraviolet by a factor of 18 illustrating the potential in the flexible fabrication technique for barium titanate photonic devices.
View details for DOI 10.1002/smll.202304355
View details for Web of Science ID 001053931300001
View details for PubMedID 37621040
- Mechanistic Insights into Aldehyde Production from Electrochemical CO2 Reduction on CuAg Alloy via Operando X-ray Measurements ACS CATALYSIS 2023: 9379-9391
- Combined, time-resolved, in situ neutron reflectometry and X-ray diffraction analysis of dynamic SEI formation during electrochemical N-2 reduction ENERGY & ENVIRONMENTAL SCIENCE 2023
- A Versatile Li0.5FePO4 Reference Electrode for Nonaqueous Electrochemical Conversion Technologies ACS ENERGY LETTERS 2022: 230-235
- Self-assembled materials for electrochemical energy storage MRS BULLETIN 2020; 45 (10): 815–22