Photoelectrochemical (PEC) water splitting is an attractive strategy for the large‐scale production of renewable hydrogen from water. Developing cost‐effective, active and stable semiconducting ...photoelectrodes is extremely important for achieving PEC water splitting with high solar‐to‐hydrogen efficiency. Perovskite oxides as a large family of semiconducting metal oxides are extensively investigated as electrodes in PEC water splitting owing to their abundance, high (photo)electrochemical stability, compositional and structural flexibility allowing the achievement of high electrocatalytic activity, superior sunlight absorption capability and precise control and tuning of band gaps and band edges. In this review, the research progress in the design, development, and application of perovskite oxides in PEC water splitting is summarized, with a special emphasis placed on understanding the relationship between the composition/structure and (photo)electrochemical activity.
Among the most important classes of materials for the application as electrodes for photoelectrochemical (PEC) water splitting are perovskite oxides. In this Review, recent progress about the development of high‐performance perovskite oxide based electrodes for PEC water splitting is discussed. The design strategies, challenges and perspectives of perovskite oxides as electrodes for PEC water splitting are also presented.
One challenge for the commercial development of solid oxide fuel cells as efficient energy-conversion devices is thermo-mechanical instability. Large internal-strain gradients caused by the mismatch ...in thermal expansion behaviour between different fuel cell components are the main cause of this instability, which can lead to cell degradation, delamination or fracture
. Here we demonstrate an approach to realizing full thermo-mechanical compatibility between the cathode and other cell components by introducing a thermal-expansion offset. We use reactive sintering to combine a cobalt-based perovskite with high electrochemical activity and large thermal-expansion coefficient with a negative-thermal-expansion material, thus forming a composite electrode with a thermal-expansion behaviour that is well matched to that of the electrolyte. A new interphase is formed because of the limited reaction between the two materials in the composite during the calcination process, which also creates A-site deficiencies in the perovskite. As a result, the composite shows both high activity and excellent stability. The introduction of reactive negative-thermal-expansion components may provide a general strategy for the development of fully compatible and highly active electrodes for solid oxide fuel cells.
An ideal solid oxide fuel cell (SOFC) cathode should meet multiple requirements, i.e., high activity for oxygen reduction reaction (ORR), good conductivity, favorable stability, and sound ...thermo‐mechanical/chemical compatibility with electrolyte, while it is very challenging to achieve all these requirements based on a single‐phase material. Herein, a cost‐effective multi‐phase nanocomposite, facilely synthesized through smart self‐assembly at high temperature, is developed as a near‐ideal cathode of intermediate‐temperature SOFCs, showing high ORR activity (an area‐specific resistance of ≈0.028 Ω cm2 and a power output of 1208 mW cm−2 at 650 °C), affordable conductivity (21.5 S cm−1 at 650 °C), favorable stability (560 h operation in single cell), excellent chemical compatibility with Sm0.2Ce0.8O1.9 electrolyte, and reduced thermal expansion coefficient (≈16.8 × 10−6 K−1). Such a nanocomposite (Sr0.9Ce0.1Fe0.8Ni0.2O3–δ) is composed of a single perovskite main phase (77.2 wt%), a Ruddlesden–Popper (RP) second phase (13.3 wt%), and surface‐decorated NiO (5.8 wt%) and CeO2 (3.7 wt%) minor phases. The RP phase promotes the oxygen bulk diffusion while NiO and CeO2 nanoparticles facilitate the oxygen surface process and O2− migration from the surface to the main phase, respectively. The strong interaction between four phases in nanodomain creates a synergistic effect, leading to the superior ORR activity.
A cobalt‐free multi‐phase nanocomposite with a superior electrochemical activity for oxygen reduction is developed as a near‐ideal cathode of intermediate‐temperature solid oxide fuel cells (SOFCs) via a smart self‐assembly strategy. Sr0.9Ce0.1Fe0.8Ni0.2O3–δ is a highly promising cathode material for SOFCs, suitable for the efficient and stable operation at the intermediate‐temperature range.
The development of cost‐effective and high‐performance electrocatalysts for the hydrogen evolution reaction (HER) is one critical step toward successful transition into a sustainable green energy ...era. Different from previous design strategies based on single parameter, here the necessary and sufficient conditions are proposed to develop bulk non‐noble metal oxides which are generally considered inactive toward HER in alkaline solutions: i) multiple active sites for different reaction intermediates and ii) a short reaction path created by ordered distribution and appropriate numbers of these active sites. Computational studies predict that a synergistic interplay between the ordered oxygen vacancies (at pyramidal high‐spin Co3+ sites) and the O 2p ligand holes (OLH; at metallic octahedral intermediate‐spin Co4+ sites) in RBaCo2O5.5+δ
(δ = 1/4; R = lanthanides) can produce a near‐ideal HER reaction path to adsorb H2O and release H2, respectively. Experimentally, the as‐synthesized (Gd0.5La0.5)BaCo2O5.75 outperforms the state‐of‐the‐art Pt/C catalyst in many aspects. The proof‐of‐concept results reveal that the simultaneous possession of ordered oxygen vacancies and an appropriate number of OLH can realize a near‐optimal synergistic catalytic effect, which is pivotal for rational design of oxygen‐containing materials.
The necessary and sufficient conditions to design highly active hydrogen‐evolving electrocatalysts are proposed: i) multiple active sites for various reaction intermediates and ii) a short reaction path. The as‐synthesized (Gd0.5La0.5)BaCo2O5.75 material, with ordered oxygen vacancies and an appropriate number of oxygen 2p holes, achieves a near‐optimal synergistic catalytic effect and makes a breakthrough in the activity of non‐noble metal oxides.
Due to the high energy density, mature production technology, ease of storage and transportation, and the no carbon/sulfur nature of ammonia fuel, direct-ammonia solid oxide fuel cells (DA-SOFCs) ...have received rapidly increasing attention, showing distinct advantages over H2-fueled SOFCs and low-temperature fuel cells. However, DA-SOFCs with conventional Ni-based cermet anodes still suffer from several drawbacks, including serious sintering and inferior activity for ammonia decomposition, strongly limiting the large-scale applications. To tackle the above-mentioned issues, exsolved NiCo nanoparticles decorated double perovskite oxides are fabricated and employed as high-performance anodes for DA-SOFCs in this work. By optimizing the Ni doping amount in Sr2CoMo1−xNixO6−δ (x = 0.1, 0.2 and 0.3), the reduced Sr2CoMo0.8Ni0.2O6−δ (r-SCMN2) anode exhibits superb catalytic activity for ammonia cracking reaction and high anti-sintering capability. More specifically, the electrolyte-supported single cell with r-SCMN2 nanocomposite anode delivers superior power outputs and operational durability in ammonia fuel as compared with other r-SCMN anodes owing to the significantly promoted nanoparticle exsolution and stronger interaction between alloy nanoparticles and the support. In summary, this study presents an effective strategy for the design of efficient and stable nanocomposite anodes for DA-SOFCs.
Titanium dioxide mesoporous microspheres with high surface area was successfully prepared by a facile one-step hydrothermal approach using polyethylene glycol (PEG, MW 200) as the soft template. ...Study shows that ∼15 nm TiO2 nanoparticles was assembled into ∼1.1 μm mesoporous microspheres. The Brunauer-Emmett-Teller surface area of TiO2 microsphere is up to 137 m2/g. TiO2 mesoporous microspheres were fabricated onto the surface of fluorine-doped tin oxide glass and used as the photoanode of dye-sensitized solar cells, which exhibits an open circuit photovoltage of 0.80 V and an overall conversion efficiency of 6.6%. Owing to the enhanced dye loading and light-harvesting efficiency, a 26% improvement in the overall conversion efficiency was achieved when compared with the commercial Degussa P25 nanoparticles.
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► TiO2 mesoporous spheres (TMS) was prepared and used as photoanodes in DSSC. ► TMS can provide a notably high surface area for dye loading. ► The suitable size of TMS enhance the light-scattering capability. ► A 26% improvement in the overall conversion efficiency was achieved when compared with Degussa P25.
Direct ammonia solid oxide fuel cell (DA‐SOFC) is superior to low‐temperature direct ammonia fuel cell using anion exchange membrane because of much improved anode reaction kinetics at elevated ...temperature. However, significant performance degradation due to severe sintering of conventional nickel cermet anode under operating conditions is a big challenge for realizing its practical use. Herein, a high‐performance anode based on La0.55Sr0.30TiO3−δ (LST) perovskite substrate with its surface decorated with in situ exsolved and strongly coupled NiCo alloy nanoparticles (NPs) is designed and fabricated for DA‐SOFCs, exhibiting superior catalytic activity for NH3 decomposition reaction due to balanced NH3 adsorption and N2 desorption processes. An electrolyte‐supported single cell with infiltrated NiCo/LST on Sm0.2Ce0.8O1.9 scaffold anode delivers a maximum power density of 361 mW cm−2 at 800 °C in NH3 fuel, superior to similar SOFCs with Ni or Co NP‐decorated LST based anodes (161 and 98 mW cm−2). Furthermore, the SOFC with this newly developed anode displays favorable operational stability without obvious performance degradation at 700 °C for a test period of ≈120 h, attributed to its high antisintering capability. This study provides some strategies to develop highly active, stable, and antisintering perovskite‐based nanocomposite for DA‐SOFCs, facilitating the practical use of this technology.
An infiltrated NiCo alloy nanoparticle decorated perovskite oxide is developed as highly active, stable, and antisintering anode for direct‐ammonia solid oxide fuel cells (DA‐SOFCs) via an infiltration–calcination–reduction process. This composite is a highly promising anode material for DA‐SOFCs, which also provides some guidelines for the design of perovskite‐based nanocomposite for DA‐SOFCs.
Compared with conventional oxygen-ion-conducting solid oxide fuel cells (O–SOFCs), proton ceramic fuel cells (PCFCs) are more attractive for low-temperature operation due to their smaller activation ...energy and higher ionic conductivity at reduced temperatures. However, most of the PCFCs still exhibit lower power outputs than O–SOFCs until now due to the lack of suitable and high-performance cathode materials. Cobalt (Co)-based perovskite oxides have been widely employed as cathodes for PCFCs, and suffer from poor thermo-mechanical compatibility with the electrolyte and inferior structural stability. Herein, Co-free triple-conducting perovskite-based nanocomposites are reported as highly active and stable cathodes for PCFCs. By tailoring the Ce/Y co-doping amounts in BaFeO3−δ, Ba(Ce0.8Y0.2)xFe1−xO3−δ (x = 0.1, 0.2 and 0.3) perovskites experience a phase transformation from a single-phase (x = 0.1, O2−/e− conducting) into a composite (x = 0.2 and 0.3, O2−/e− and H+/e− conducting) to achieve triple-conducting capability. The optimized BaCe0.16Y0.04Fe0.8O3−δ nanocomposite cathode displays superior activity for the oxygen reduction reaction (ORR) with low area-specific resistances of 0.27 and 1.49 Ω cm2 at 600 and 500 °C, respectively, surpassing most of the reported Co-free PCFC cathodes. The BaCe0.16Y0.04Fe0.8O3−δ cathode also exhibits superior thermo-mechanical compatibility with BaZr0.1Ce0.7Y0.1Yb0.1O3−δ electrolyte and improved CO2 tolerance due to the strong interaction between O2−/e− and H+/e− conducting phases and the optimized dual-phase composition. Consequently, an anode-supported single cell with the BaCe0.16Y0.04Fe0.8O3−δ cathode delivers a high peak power density of 829 mW cm−2 at 650 °C and a durable operation for ∼450 h at 550 °C. This work provides a highly promising Co-free cathode for PCFCs, which may accelerate the commercialization of this technology.
In this study, TiO2 wedgy nanotubes with rectangular cross-sections were fabricated on transparent conductive substrates by using TiO2 nanorods as the precursor via the anisotropic etching route. ...TiO2 nanotubes with V-shaped hollow structure and the special crystal plane exposed on the tube wall possess nature of high surface area for more dye molecules absorption, and the strong light scattering effects and dual-channel for effective electron transport of the TiO2 V-shaped nanotubes based dye-sensitized solar cell exhibit a remarkable photovoltaic enhancement compared with the TiO2 nanorods. The photoanode based on our V-shaped TiO2 nanotubes with a length of 1.5I14m show a 123% increase of the dye loading and a 182% improvement in the overall conversion efficiency when compared with 4I14m rutile TiO2 nanorods photoanode.
Solid oxide fuel cells (SOFCs) as one of the clean electrochemical energy conversion devices have acquired increasing attention recently due to the high efficiency, low emission, and excellent fuel ...flexibility. Nevertheless, the practical application of SOFCs is hindered by poor stability and high cost. Thus, lowering the operating temperatures is critical to increase the lifetime and reduce the cost of SOFCs. However, the electrolyte and electrode materials used in high-temperature SOFCs suffer from insufficient ionic conductivity and poor electrocatalytic activity at lower operating temperatures, respectively. Nanomaterials and relevant nanotechnologies have great potential to enhance the performance of SOFCs operated at lower temperatures because of the enlarged surface area, distinct surface, and interface properties. Among various nanotechnologies, pulsed laser deposition (PLD) has been widely employed in SOFCs to reduce the operating temperature. Herein, we present an in-time review about the PLD-involved fabrication of key components in intermediate-temperature (IT) SOFCs in terms of cathodes, electrolytes, anodes, and interlayers. The superiority of the PLD technique to other traditional fabrication methods is emphasized, and design strategies for the key components in IT-SOFCs are presented and discussed. We also point out the trends, current challenges, and future directions that exist in this dynamic field. This review will inspire substantial interests from various disciplines and provide some valuable guidance for future development of PLD-involved energy storage and conversion devices.
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