Carbonate-superstructured solid fuel cells with hydrocarbon fuels

Modification Strategies for Development of 2D Material-Based Electrocatalysts for Alcohol Oxidation Reaction

2D materials, such as graphene, MXenes (metal carbides and nitrides), graphdiyne (GDY), layered double hydroxides, and black phosphorus, are widely used as electrocatalyst supports for alcohol oxidation reactions (AORs) owing to their large surface area and unique 2D charge transport channels. Furthermore, the development of highly efficient electrocatalysts for AORs via tuning the structure of 2D support materials has recently become a hot area. This article provides a critical review on modification strategies to develop 2D material-based electrocatalysts for AOR. First, the principles and influencing factors of electrocatalytic oxidation of alcohols (such as methanol and ethanol) are introduced. Second, surface molecular functionalization, heteroatom doping, and composite hybridization are deeply discussed as the modification strategies to improve 2D material catalyst supports for AORs. Finally, the challenges and perspectives of 2D material-based electrocatalysts for AORs are outlined. This review will promote further efforts in the development of electrocatalysts for AORs.

Gradient Functional Layer Anode for Carbonate-Superstructured Solid Fuel Cells with Ethane Fuel

Carbonate-superstructured solid fuel cells (CSSFCs) are an emerging type of fuel cells with high flexibility of fuels. However, using ethane fuel for solid fuel cells is a great challenge due to serious degradation of their anodes. Herein, this critical issue is solved by creating a novel gradient functional layer anode for CSSFCs. First, a finer-scale anode with a larger surface area is demonstrated to provide more active sites for the internal reforming reaction of ethane, achieving a 60% higher ethane conversion rate and 40% lower polarization resistance than conventional anodes. Second, incorporating a gradient functional layer into the anode results in an additional 50% enhancement in the peak power density of CSSFCs to a record high value (up to 241 mW cm-2) with dry ethane fuel at a low temperature of 550 °C, which is even comparable to the power density of conventional solid oxide fuel cells above 700 °C. Furthermore, the CSSFC with the gradient anode exhibits excellent durability for over 200 h. This finding provides a new strategy to develop efficient anodes for hydrocarbon fuels.

Critical Role of In-Situ-Generated Eutectic Carbonates in Superstructured Solid Fuel Cells

As a distinct type of fuel cell, a carbonate-superstructured solid fuel cell (CSSFC), which possesses excellent performance and easy fabrication as well as low cost, was recently invented by our group. Herein, we demonstrated the critical role of the in-situ-generated eutectic carbonate phase in CSSFC. Namely, the in-situ generation of eutectic Li2CO3/Na2CO3 system increased the oxygen ionic conductivity of Ce0.8Sm0.2O1.9 solid electrolyte by 20 times (from 3.5 × 10-3 to 7.3 × 10-2 S cm-1), leading to 6 times enhancement of CSSFC peak powder density (up to 206 mW cm-2) with methane fuel at 550 °C. This finding is extremely important for designing efficient CSSFCs.

Thermo-photo catalytic anode process for carbonate-superstructured solid fuel cells

Converting hydrocarbons and greenhouse gases (i.e., carbon dioxide, CO2) directly into electricity through fuel cells at intermediate temperatures (450 to 550 °C) remains a significant challenge, primarily due to the sluggish activation of C-H and C=O bonds. Here, we demonstrated a unique strategy to address this issue, in which light illumination was introduced into the thermal catalytic CO2 reforming of ethane in the anode as a unique thermo-photo anode process for carbonate-superstructured solid fuel cells. The light-enhanced fuel activation led to excellent cell performance with a record-high peak power density of 168 mW cm-2 at an intermediate temperature of 550 °C. Furthermore, no degradation was observed during ~50 h operation. Such a successful integration of photo energy into the fuel cell system provides a new direction for the development of efficient fuel cells.

Root Cause Analysis of Degradation in Protonic Ceramic Electrochemical Cell with Interfacial Electrical Sensors Using Data-Driven Machine Learning

Protonic ceramic electrochemical cells (PCECs) offer promising paths for energy storage and conversion. Despite considerable achievements made, PCECs still face challenges such as physiochemical compatibility between componenets and suboptimal solid-solid contact at the interfaces between the electrolytes and electrodes. In this study, a novel approach is proposed that combines in situ electrochemical characterization of interfacial electrical sensor embedded PCECs and machine learning to quantify the contributions of different cell components to total degradation, as well as to predict the remaining useful life. The experimental results suggest that the overpotential induced by the oxygen electrode is 48% less than that of oxygen electrode/electrolyte interfacial contact for up to 1171 h. The data-driven machine learning simulation predicts the RUL of up to 2132 h. The root cause of degradation is overpotential increase induced by oxygen electrode, which accounts for 82.9% of total cell degradation. The success of the failure diagnostic model is demonstrated by its consistency with degradation modes that do not manifest in electrolysis fade during early real operations. This synergistic approach provides valuable insights into practical failure diagnosis of PCECs and has the potential to revolutionize their development by enabling improved performance prediction and material selection for enhanced durability and efficiency.

3D graphene: synthesis, properties, and solar cell applications

Three-dimensional (3D) graphene is one of the most important nanomaterials. This feature article highlights the advancements, with an emphasis on contributions from our group, in the synthesis of 3D graphene-based materials and their utilization in solar cells. Chemistries of graphene oxides, hydrocarbons, and alkali metals are discussed for the synthesis of 3D graphene materials. Their performances in dye-sensitized solar cells and perovskite solar cells (as counter electrodes, photoelectrodes, and electron extracting layers) were correlatively analyzed with their properties/structures (accessible surface area, electrical conductivity, defects, and functional groups). The challenges and prospects for their applications in photovoltaic solar cells are outlined.

Ultrafine, Dual-Phase, Cation-Deficient PrBa0.8Ca0.2Co2O5+δ Air Electrode for Efficient Solid Oxide Cells

Nanostructured air electrodes play a crucial role in improving the electrocatalytic activity of oxygen reduction and evolution reactions in solid oxide cells (SOCs). Herein, we report the fabrication of a nanostructured BaCoO₃-decorated cation-deficient PrBa_0.8Ca_0.2Co₂O_5+δ (PBCC) air electrode via a combined modification and direct assembly approach. The modification approach endows the dual-phase air electrode with a large surface area and abundant oxygen vacancies. An intimate air electrode-electrolyte interface is in situ constructed with the formation of a catalytically active Co₃O₄ bridging layer via electrochemical polarization. The corresponding single cell exhibits a peak power density of 2.08 W cm^-2, an electrolysis current density of 1.36 A cm^-2 at 1.3 V, and a good operating stability at 750 °C for 100 h. This study provides insights into the rational design and facile utilization of an active and stable nanostructured air electrode of SOCs.

Ni/NiO Exsolved Perovskite La0.2Sr0.7Ti0.9Ni0.1O3-δ for Semiconductor-Ionic Fuel Cells: Roles of Electrocatalytic Activity and Physical Junctions

A semiconductor-ionic fuel cell (SIFC) is recognized as a promising technology and an alternative approach to reduce the operating temperature of solid oxide fuel cells. The development of alternative semiconductors substituting easily reduced transition metal oxide is a great challenge as high activity and durability should be satisfied simultaneously. In this study, the B-site Ni-doped La_0.2Sr_0.7Ti_0.9Ni_0.1O_3-δ (LSTN) perovskite is synthesized and used as a potential semiconductor for SIFC. The in situ exsolution and A-site deficiency strategy enable the homogeneous decoration of Ni/NiO nanoparticles as reactive sites to improve the electrode reaction kinetics. It also supports the formation of basic ingredient of the Schottky junction to improve the charge separation efficiency. Furthermore, additional symmetric Ni_0.8Co_0.15Al_0.05LiO_2-δ (NCAL) electrocatalytic electrode layers significantly enhance the electrode reaction activity and cells' charge separation efficiency, as confirmed by the superior open circuit voltage of 1.13 V (close to Nernst's theoretical value) and peak power density of 650 mW cm^-2 at 550 °C, where the latter is one order of magnitude higher than NCAL electrode-free SIFC. Additionally, a bulk heterojunction effect is proposed to illustrate the electron-blocking and ion-promoting processes of the semiconductor-ionic composite electrolyte in SIFCs, based on the energy band values of the applied materials. Overall, we found that the energy conversion efficiency of novel SIFC can be remarkably improved through in situ exsolution and intentional introduction of the catalytic functionality.