7 research outputs found
Splicing the active phases of copper/cobalt-based catalysts achieves high-rate tandem electroreduction of nitrate to ammonia
Electrocatalytic recycling of waste nitrate () to valuable ammonia () at ambient conditions is a green and appealing alternative to the Haber−Bosch process. However, the reaction requires multi-step electron and proton transfer, making it a grand challenge to drive high-rate synthesis in an energy-efficient way. Herein, we present a design concept of tandem catalysts, which involves coupling intermediate phases of different transition metals, existing at low applied overpotentials, as cooperative active sites that enable cascade -to- conversion, in turn avoiding the generally encountered scaling relations. We implement the concept by electrochemical transformation of Cu−Co binary sulfides into potential-dependent core−shell and Co/CoO phases. Electrochemical evaluation, kinetic studies, and in−situ Raman spectra reveal that the inner phases preferentially catalyze reduction to , which is rapidly reduced to at the nearby Co/CoO shell. This unique tandem catalyst system leads to a -to- Faradaic efficiency of 93.3 2.1% in a wide range of concentrations at pH 13, a high yield rate of 1.17 mmol in 0.1 M at −0.175 V vs. RHE, and a half-cell energy efficiency of ~36%, surpassing most previous reports
Fuel Exhaling Fuel Cell
State-of-the-art
proton exchange membrane fuel cells (PEMFCs) anodically
inhale H<sub>2</sub> fuel and cathodically expel water molecules.
We show an unprecedented fuel cell concept exhibiting cathodic fuel
exhalation capability of anodically inhaled fuel, driven by the neutralization
energy on decoupling the direct acid–base chemistry. The fuel
exhaling fuel cell delivered a peak power density of 70 mW/cm<sup>2</sup> at a peak current density of 160 mA/cm<sup>2</sup> with a
cathodic H<sub>2</sub> output of ∼80 mL in 1 h. We illustrate
that the energy benefits from the same fuel stream can at least be
doubled by directing it through proposed neutralization electrochemical
cell prior to PEMFC in a tandem configuration
An Electrochemical Wind Velocity Sensor
Electrochemical
interfaces invariably generate unipolar electromotive
force because of the unidirectional nature of electrochemical double
layers. Herein we show an unprecedented generation of a time varying
bipolar electric field between identical half-cell electrodes induced
by tailored interfacial migration of magnetic particles. The periodic
oscillation of a bipolar electric field is monotonically correlated
with velocity-dependent torque, opening new electrochemical pathways
targeting velocity monitoring systems
An Electrochemical Wind Velocity Sensor
Electrochemical
interfaces invariably generate unipolar electromotive
force because of the unidirectional nature of electrochemical double
layers. Herein we show an unprecedented generation of a time varying
bipolar electric field between identical half-cell electrodes induced
by tailored interfacial migration of magnetic particles. The periodic
oscillation of a bipolar electric field is monotonically correlated
with velocity-dependent torque, opening new electrochemical pathways
targeting velocity monitoring systems
Structure‐performance relationship of electrocatalysts for oxygen evolution, isopropanol oxidation, and glycerol oxidation
Mitigating high energy costs related to sustainable H2 production via water electrolysis is important to make this process commercially viable. Possible approaches are the investigation of low-cost, highly active oxygen evolution reaction (OER) catalysts and the exploration of alternative anode reactions, such as the electrocatalytic isopropanol oxidation reaction (iPOR) or the glycerol oxidation reaction (GOR), offering the possibility of simultaneously lowering the anodic overpotential and generating value-added products. A suitable class of catalysts are non-noble metal-based perovskites with the general formula , featuring rare-earth metal cations at the A- and transition metals at the B-site. We synthesised a series of materials with x=0–0.70 by automated co-precipitation at constant pH and subsequent calcination at 800°C. X-ray diffraction studies revealed that the phase purity was preserved in samples with x0.3. The activity towards the OER, iPOR, and GOR was investigated by rotating disk electrode voltammetry, showing a relation between structure and metal composition with the activity trends observed for the three reactions. Additionally, GOR product analysis via high-performance liquid chromatography (HPLC) was conducted after 24 and 48 h electrolysis in a circular flow-through cell setup, pointing out a trade-off between activity and selectivity