Preparation and Characterization of Mixed-Valent Nickel Oxide/Nickel Hexacyanoferrate Hybrid Films and Their Electrocatalytic Properties

Electrolyte Effects on the Stabilization of Prussian Blue Analogue Electrodes in Aqueous Sodium-Ion Batteries

Aqueous sodium-ion batteries based on Prussian Blue Analogues (PBA) are considered as promising and scalable candidates for stationary energy storage systems, where longevity and cycling stability are assigned utmost importance to maintain economic viability. Although degradation due to active material dissolution is a common issue of battery electrodes, it is hardly observable directly due to a lack of in operando techniques, making it challenging to optimize the performance of electrodes. By operating Na₂Ni[Fe(CN)₆] and Na₂Co[Fe(CN)₆] model electrodes in a flow-cell setup connected to an inductively coupled plasma mass spectrometer, in this work, the dynamics of constituent transition-metal dissolution during the charge-discharge cycles was monitored in real time. At neutral pHs, the extraction of nickel and cobalt was found to drive the degradation process during charge-discharge cycles. It was also found that the nature of anions present in the electrolytes has a significant impact on the degradation rate, determining the order ClO₄^- > NO₃^- > Cl^- > SO₄^2- with decreasing stability from the perchlorate to sulfate electrolytes. It is proposed that the dissolution process is initiated by detrimental specific adsorption of anions during the electrode oxidation, therefore scaling with their respective chemisorption affinity. This study involves an entire comparison of the effectiveness of common stabilization strategies for PBAs under very fast (dis)charging conditions at 300C, emphasizing the superiority of highly concentrated NaClO₄ with almost no capacity loss after 10 000 cycles for Na₂Ni[Fe(CN)₆].

Site-specific immobilization of a (His)6-tagged acetylcholinesterase on nickel nanoparticles for highly sensitive toxicity biosensors

This paper reports site-specific affinity immobilization of (His)6-tagged acetylcholinesterase (AChE) onto Ni/NiO nanoparticles for the development of an electrochemical screen-printed biosensor for the detection of organophosphate pesticides. The method is based on the specific affinity binding of the His-tagged enzyme to oxidized nickel nanoparticle surfaces in the absence of metal chelators. This approach allows stable and oriented attachment of the enzyme onto the oxidized nickel through the external His residue in one-step procedure, allowing for fast and sensitive detection of paraoxon in the concentration range from 10(-8) to 10(-13) M. A detection limit of 10(-12) M for paraoxon was obtained after 20 min incubation. This method can be used as a generic approach for the immobilization of other His-tagged enzymes for the development of biosensors.