The passivation of two high strength duplex stainless steels (HSSS) was investigated in alkaline solutions simulating the pore solution of concrete by the growth of natural and induced passive films. Induced passive films were generated both by cyclic voltammetry and by chronoamperometry. Natural passive films were spontaneously grown by the immersion of the steel in the alkaline electrolyte. These passive layers were characterised by electrochemical impedance spectroscopy, corrosion current density (i corr ) and corrosion potential (E corr ) monitoring. The effect of significant parameters, such as the pH in the HSSS/alkaline solution interface, the composition of the duplex stainless steels and the ageing of the passive layer, on the electrochemical performance of both induced and spontaneously grown passive films has been analysed. The increase of alkalinity highly influences the electrochemical performance of the passive film by promoting the formation of a passive layer with a less resistant electrochemical response. The electrochemical behaviour of the passive layer is also affected by the alloying elements like Mo or Ni. Both natural and induced passive films show similar electrochemical trend with respect to significant parameters such as the pH and the composition of the steel. The ageing of the spontaneously grown passive layer promotes a higher resistive electrochemical response which might be related to the enrichment of the passive layer in nonconducting (or semi-conducting) oxides.

Thanks to the low cost and earth's abundant potassium resources, potassium ion batteries (PIBs) have attracted much interest as alternative energy storage devices. However, there is still a great challenge...

A long-term electrochemical monitoring of the natural ageing of spontaneously passivated duplex 2304 stainless steel (SS) in the presence of increasing concentrations of chloride was carried out in the present work. The influence of the steel surface roughness on the SS pitting susceptibility was also assessed by comparing parent (P-SS) and cold-drawn (CD-SS) types. A different electrochemical response against the presence of chloride in the passive film/electrolyte interface was registered for both types of stainless steels: while a progressive destabilization of the passive layer for P-SS with pitting formation was observed at high concentrations of chloride (2 M), a more resistant behaviour against the chloride action was observed for the CD-SS, which presented a significant lower surface roughness.

Niobium pentoxide (Nb 2 O 5 ) material is a promising anode for lithium-ion batteries (LIBs) due to the outstanding cycle performance and rate capability. However, the relatively low capacity severely limits the comprehensive performance. Generally, nanoscale engineering of the morphology and chemical composition of Nb 2 O 5 anodes is employed to improve electrochemical lithium storage. In this work, we promote the reservable capacity of a sheetlike Nb 2 O 5 anode by designing nanoscale phase interfaces between the nanodomains of T-Nb 2 O 5 , M-Nb 2 O 5 , and H-Nb 2 O 5 phases, which are generated by good control over the calcination of Nb 3 O 7 F precursor at high temperatures. Microstructural and chemical analyses show that the sample calcined at 750 °C (Nb 2 O 5 -750) has optimized structural advantages to efficiently store lithium ions. When evaluated as anodes for LIBs, the Nb 2 O 5 -750 sample shows excellent lithium storage properties. In specific, the Nb 2 O 5 -750 electrode delivers a reversible capacity of 270.4 mAh g −1 at 1C after 200 cycles. At a high rate of 5C, the Nb 2 O 5 -750 electrode has a reversible capacity of 174 mAh g −1 after 800 cycles. This work provides an alternative way to improve the ion storage in the electrodes with intrinsic polymorphic structures.