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...

Producing electrolytes with high ionic conductivity has been a critical challenge in the progressive development of solid oxide fuel cells (SOFCs) for practical applications. The conventional methodology uses the ion doping method to develop electrolyte materials, e.g., samarium-doped ceria (SDC) and yttrium-stabilized zirconia (YSZ), but challenges remain. In the present work, we introduce a logical design of non-stoichiometric CeO 2-δ based on non-doped ceria with a focus on the surface properties of the particles. The CeO 2−δ reached an ionic conductivity of 0.1 S/cm and was used as the electrolyte in a fuel cell, resulting in a remarkable power output of 660 mW/cm 2 at 550°C. Scanning transmission electron microscopy (STEM) combined with electron energy-loss spectroscopy (EELS) clearly clarified that a surface buried layer on the order of a few nanometers was composed of Ce 3+ on ceria particles to form a CeO 2−δ @CeO 2 core-shell heterostructure. The oxygen deficient layer on the surface provided ionic transport pathways. Simultaneously, band energy alignment is proposed to address the short circuiting issue. This work provides a simple and feasible methodology beyond common structural (bulk) doping to produce sufficient ionic conductivity. This work also demonstrates a new approach to progress from material fundamentals to an advanced lowtemperature SOFC technology.

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Interface engineering holds huge potential for enabling exceptional physical properties in heterostructure materials via tuning properties at the atomic level. In this study, a heterostructure built by a new redox stable semiconductor SrFe 0.75 Ti 0.25 O 3−δ (SFT) and an ionic conductor Sm 0.25 Ce 0.75 O 2 (SDC) is reported. The SFT−SDC heterostructure exhibits a high ionic conductivity >0.1 S/cm at 520 °C, which is 1 order of magnitude higher than that of bulk SDC. When it was applied into the fuel cell, the SFT−SDC can realize favorable electrolyte functionality and result in an excellent power density of 920 mW cm −2 at 520 °C. The prepared SFT−SDC heterostructure materials possess both electronic and ionic conduction, where electron states modulate local electrical field to facilitate ion transport. Further investigations to calculate the structure and electronic structure/state of SFT and SDC are done using density functional theory (DFT). It is found that the reconstruction of the energy band at interfaces is responsible for such enhanced ionic conductivity and cell power output. The current study about the perovskite-based heterostructure presents a novel strategy for developing advanced ceramic fuel cells. KEYWORDS: heterostructure, SrFe 0.75 Ti 0.25 O 3-δ -Sm 0.25 Ce 0.75 O 2−δ (SFT−SDC), ionic conduction, band structure, built-in field