Interest in low-temperature operation of solid oxide fuel cells is growing. Recent advances in perovskite phases have resulted in an efficient H + /O 2- /e - triple-conducting electrode BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3-δ for low-temperature fuel cells. Here, we further develop BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3-δ for electrolyte applications by taking advantage of its high ionic conduction while suppressing its electronic conduction through constructing a BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3-δ -ZnO p-n heterostructure. With this approach, it has been demonstrated that BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3-δ can be applied in a fuel cell with good electrolyte functionality, achieving attractive ionic conductivity and cell performance. Further investigation confirms the hybrid H + /O 2- conducting capability of BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3-δ -ZnO. An energy band alignment mechanism based on a p-n heterojunction is proposed to explain the suppression of electronic conductivity and promotion of ionic conductivity in the heterostructure. Our findings demonstrate that BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3-δ is not only a good electrode but also a highly promising electrolyte. The approach reveals insight for developing advanced low-temperature solid oxide fuel cell electrolytes.

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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.

BHJ) structure. [ 9 ] The BHJ requires delicate tailoring of n-and p-particles in order to avoid the electronic short-circuit problem and make fuel cell function properly. [ 9 ] Hereby, we introduce the different Schottky junction type FC confi guration by means of combined nano and composite approach that is even simpler and more effective than EFFC.In a Schottky junction (SJ) FC device, a potential can be built up simply at the interface between a metal and an n-or p-type semiconductor, which is also termed as the Schottky barrier. [ 10 ] Based on this principle and making use of the depletion layer formed between the metal and the semiconductor, different types of Schottky junction devices have been demonstrated, such as solar cells and sensors. [11][12][13][14][15][16] One well-known function of SJ is to separate electrons/holes pairs by building up internal device voltage. Moreover, it has been reported that a Schottky junction formed between mesoporous n-TiO 2 semiconductor thin fi lm and a thin metal layer (such as Pt, Cu, Co, etc.) at anode/catalysts can effectively enhance the decomposition of aqueous biomass fuel solutions in combination with an O 2 -reducing cathode in a direct biomass fuel cell. [ 17,18 ] In this paper, we show that a SJ can be applied to ceramic FCs by using a composite of ionic and semiconducting materials to combine both semiconducting and ionic transporting properties, resulting in Schottky junction FC devices.Electrochemical reactions converting fuels, e.g., hydrogen into electricity through a FC is, to a high degree, affected by the quality of the ion-conducting electrolyte, which separates the anode and cathode to avoid short-circuit, [19][20][21] and brings about complex three-component (anode/electrolyte/cathode) confi guration as well. [ 22 ] The principle of SJ FC, based on a metal-semiconductor confi guration, is illustrated in Figure 1 . Different from the conventional FC device, i.e., instead of utilizing the electrolyte separator, the built-in fi eld and the barrier of the SJ serves the function of blocking electrons or holes from crossing the metal/semiconductor interface to the opposite side, resulting in no short-circuit of the device. The metal/ p-type semiconductor junction is favored because the builtin fi eld is directed from the metal surface to the p-type material, which can facilitate the ion transportation of H + (or O 2− ) crossing the metal/semiconductor-ionic material interface through ionic conductor at the same time, as shown in Figure 1 with corresponding energy band diagram schemes.The SJ FC was constructed from a hybrid oxygen-protonconducting material Ce 0.8 Sm 0.2 O 1.9 -Na 2 CO 3 (NSDC) [ 23 ] and p-type semiconducting materials Co-Li codoped NiO (LiNi 0.85 Co 0.15 O 2-δ , LCN for short), [ 24,25 ] in a weight ratio of 60:40 forming a composite (NSDC-LCN) ( Figure S1,The fi rst fuel cell (FC) invented by Grove in 1839 [ 1 ] was an electrochemical device by using a confi guration comprised of an anode, an electrolyte, and a cathode. Building on this...

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Recently, metal‐free, heteroatom‐doped carbon nanomaterials have emerged as promising electrocatalysts for the oxygen evolution reaction (OER), but their synthesis is a tedious process involving energy‐wasting calcination. Molecular electrocatalysts offer attractive catalysts for the OER. Here, phytic acid (PA) was selected to investigate the OER activity of carbons in organic molecules by DFT calculations and experiments. Positively charged carbons on PA were very active towards the OER. The PA molecules were fixed into a porous, conductive hydrogel with a superhydrophilic surface. This outperformed most metal‐free electrocatalysts. Besides the active sites on PA, the high OER activity was also related to the porous and conductive networks on the hydrogel, which allowed fast charge and mass transport during the OER. Therefore, this work provides a metal‐free, organic‐molecule‐based electrocatalyst to replace carbon nanomaterials for efficient OER.

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