We report a confined proton transportation in the CeO 2 /CeO 2−δ core−shell structure to build up proton shuttles, leading to a super proton conductivity of 0.16 S cm −1 for the electrolyte and advanced fuel cell performance, 697 mW cm −2 at 520 °C. The semiconductor nature of the CeO 2 (i-type) core and the CeO 2−δ (n-type) shell reveals a unique proton transport mechanism based on the charged layers formed at the interface of the CeO 2−δ /CeO 2 heterostructure. Two key factors of this structure confine proton transport to the particle surface. The first is the high concentration of oxygen vacancies in the surface layer, which benefits proton conduction. The second is a depletion region created by the core−shell interface that allows proton migration only on the surface layer rather than into the bulk CeO 2 . The constrained surface region of the CeO 2−δ builds up continuous proton shuttles. This work presents a new methodology and understanding for proton transport in general oxides and a new generation proton ceramic fuel cells.

As a promising alternative for lithium ion batteries, room-temperature sodium ion batteries (SIBs) have become one significant research frontier of energy storage devices although there are still many difficulties to be overcome. For the moment, the studies still concentrate on the preparation of new electrode materials for SIBs to meet the applicability. Herein, one new P2-Na2/3Ni1/3Mn5/9Al1/9O2 (NMA) cathode material is successfully prepared via a simple and facile liquid-state method. The prepared NMA is layered transition metal oxide, which can keep stable crystal structure during sodiation/desodiation as demonstrated by the ex situ X-ray diffraction, and its electrochemical properties can be further enhanced by connecting the cake-like NMA microparticles with reduced graphene oxide (RGO) using a ball milling method. Electrochemical tests show that the formed RGO-connected NMA (NMA/RGO) can deliver a higher reversible capacity of up to 138 mAh g(-1) at 0.1 C and also exhibit a superior high-rate capabilities and cycling stability in comparison to pure NMA. The much improved properties should be attributed to the reduced particle size and improvement of electrical conductivity and apparent Na(+) diffusion due to RGO incorporation, which is comprehensively verified by the electrochemical technologies of galvanostatic intermittent titration technique, electrochemical impedance spectroscopy and cyclic voltammetry at various scan rate as well as ex-situ X-ray diffraction studies.

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Multifunctional semiconductor cubic silicon carbide (3C-SiC) is employed for fuel cell electrolyte, which has never been used before. n-type 3C-SiC can be individually employed as the electrolyte in fuel cells, but delivers insufficient open circuit voltage and minuscule current density due to its electronic dominant property. By introducing n-type ZnO to form an n–n 3C-SiC/ZnO heterostructure, significant enhancements in the ionic conductivity of 0.12 S/cm and fuel cell performance of 270 mW cm−2 are achieved at 550 °C. It is found that the energy band bending and build-in electric field of the heterostructure play the pivotal role in the ionic transport and suppressing the electronic conduction of 3C-SiC, leading to a markable material ionic property and fuel cell performance. These findings suggest that 3C-SiC can be tuned to ionic conducting electrolyte for fuel cell applications through the heterostructure approach and energy band alignment methodology.

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