Splicing the active phases of copper/cobalt-based catalysts achieves high-rate tandem electroreduction of nitrate to ammonia

Electrocatalytic recycling of waste nitrate ($NO_{3}$$^-$) to valuable ammonia ($NH_3$) at ambient conditions is a green and appealing alternative to the Haber−Bosch process. However, the reaction requires multi-step electron and proton transfer, making it a grand challenge to drive high-rate $NH_3$ synthesis in an energy-efficient way. Herein, we present a design concept of tandem catalysts, which involves coupling intermediate phases of different transition metals, existing at low applied overpotentials, as cooperative active sites that enable cascade $NO_{3}$$^-$-to-$NH_3$ 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 $Cu/CuO_x$ and Co/CoO phases. Electrochemical evaluation, kinetic studies, and in−situ Raman spectra reveal that the inner $Cu/CuO_x$ phases preferentially catalyze $NO_{3}$$^-$ reduction to $NO_{2}$$^-$, which is rapidly reduced to $NH_3$ at the nearby Co/CoO shell. This unique tandem catalyst system leads to a $NO_{3}$$^-$-to-$NH_3$ Faradaic efficiency of 93.3 $\pm$ 2.1% in a wide range of $NO_{3}$$^-$ concentrations at pH 13, a high $NH_3$ yield rate of 1.17 mmol $cm^{−2} h^{−1}$ in 0.1 M $NO_{3}$$^-$ 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 H₂ 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/cm² at a peak current density of 160 mA/cm² with a cathodic H₂ 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 LaFe1‐xCoxO3LaFe_{1‐x}Co_{x}O_{3} 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 $ABO_{3}$, featuring rare-earth metal cations at the A- and transition metals at the B-site. We synthesised a series of $LaFe_{1‐x}Co_{x}O_{3}$ 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 x$\leq$0.3. 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