Ya-Qian Zhang

Novel layered solid oxide fuel cells with multiple-twinned Ni0.8Co0.2 nanoparticles: the key to thermally independent CO2 utilization and power-chemical cogeneration

To energy-efficiently offset our carbon footprint, we herein developed a novel CH4–CO2 dry reforming process to co-produce electricity and CO-concentrated syngas, which takes advantage of the selective oxidation of H2 in high performance proton-conducting solid oxide fuel cells (SOFCs). In these cells, an additional functional layer, consisting of a Ni0.8Co0.2–La0.2Ce0.8O1.9 (NiCo–LDC) composite, was successfully incorporated into the anode support, forming a layered SOFC configuration. The multiple-twinned bimetallic nanoparticles were then proven to have superior activity towards in situ dry reforming. In comparison to the conventional design, this layered SOFC demonstrated drastically improved CO2 resistance as well as internal reforming efficiency (CO2 conversion reached 91.5% at 700 °C), and up to 100 h galvanostatic stability in a CH4–CO2 feedstream at 1 A cm−2. More importantly, H2 was effectively and exclusively converted by electrochemical oxidation, yielding no CO2 but CO concentrated syngas in the anode effluent. The maximum power density exceeded 910 mW cm−2 at 700 °C with a polarization resistance as low as 0.121 Ω cm2. Consequently, the heat released by H2 electrochemical oxidation fully compensated for that required by the extremely endothermic dry reforming reaction, making the entire process thermally self-sufficient. We also showed that the layered design was beneficial in terms of decreasing coking and increasing CO2 resistance of the SOFC in the mixed CO2 and CH4 feedstock. This novel process promises to play a pivotal role in future CO2 conversion and utilization.

New Opportunity for in Situ Exsolution of Metallic Nanoparticles on Perovskite Parent

One of the main challenges for advanced metallic nanoparticles (NPs) supported functional perovskite catalysts is the simultaneous achievement of a high population of NPs with uniform distribution as well as long-lasting high performance. These are also the essential requirements for optimal electrode catalysts used in solid oxide fuel cells and electrolysis cells (SOFCs and SOECs). Herein, we report a facile operando manufacture way that the crystal reconstruction of double perovskite under reducing atmosphere can spontaneously lead to the formation of ordered layered oxygen deficiency and yield segregation of massively and finely dispersed NPs. The real-time observation of this emergent process was performed via an environmental transmission electron microscope. Density functional theory calculations prove that the crystal reconstruction induces the loss of coordinated oxygen surrounding B-site cations, serving as the driving force for steering fast NP growth. The prepared material shows promising capability as an active and stable electrode for SOFCs in various fuels and SOECs for CO2 reduction. The conception exemplified here could conceivably be extended to fabricate a series of supported NPs perovskite catalysts with diverse functionalities.

Highly Active and Redox-Stable Ce-Doped LaSrCrFeO-Based Cathode Catalyst for CO2 SOECs

Lanthanum chromate-based perovskite oxides have attracted great attention as the cathode materials in the high-temperature CO2 electrolysis because of its good redox stability. However, the unsatisfied electrochemical catalytic activity and insufficient adsorption of CO2 at operating temperature still hindered the further improvement of electrochemical performance and the Faraday efficiency of the electrolysis cell. In this work, the catalytic and redox active Ce was doped into A site of La0.7Sr0.3Cr0.5Fe0.5O3-δ (LSCrF) to promote the catalytic performance, and to introduce oxygen vacancies in the lattice in situ after reduction under the operational condition. The increased amount of oxygen vacancies not only facilitates the mobility of oxygen ions, but also provides favorable accommodation for chemical adsorption of CO2. The CO2 electrolysis tests demonstrated the superior electrochemical performances, higher Faraday efficiencies of the Ce-doped LSCrF cathode catalyst in comparison with that without Ce doping, indicating the perspective application of this functional material.

Anode-Engineered Protonic Ceramic Fuel Cell with Excellent Performance and Fuel Compatibility

Directly utilizing hydrocarbon fuels, particularly methane, is advantageous yet challenging in high-performance protonic ceramic fuel cells. In this work, this technological hurdle is well addressed by selective deposition of secondary electrocatalysts within the porous Ni-cermet anode. This novel strategy sheds light on the development of multifunctional porous structures for energy and catalysis applications.

Biogas to syngas: flexible on-cell micro-reformer and NiSn bimetallic nanoparticle implanted solid oxide fuel cells for efficient energy conversion

Solid oxide fuel cells (SOFCs) deliver an energy-efficient and eco-friendly pathway to convert biogas into syngas and electricity. However, many problems still need to be solved before their commercialization. Some of the disadvantages of biogas SOFC technology include coking and sulfur poisoning that lead to catalyst deactivation and large thermal gradients causing thermal stress. In this work, a novel on-cell micro-reformer and NiSn bimetallic nanoparticles were introduced into a conventional Ni-based anode for efficient and durable internal reforming of biogas. The add-on micro-reformer, consisting of tailored Ni foam supported NiSn/Al2O3 nanoclusters, exhibited excellent reforming activity and outstanding resistance to coking and sulfur poisoning. Thus, the pre-reforming process in the micro-reformer could effectively decrease the thermal gradients in the anode. Besides, the loosely filled nanoclusters showed high capability of releasing thermal stress due to their movable nature. Moreover, the yielded syngas was partially electro-oxidized in a coke/sulfur tolerant NiSn bimetallic anode to compensate the energy consumption and promote the conversion of biogas. At 850 °C and in a CH4–CO2-200 ppm H2S atmosphere, a peak power density as high as 0.946 W cm−2 was achieved. With a constant current density of 1.25 A cm−2, the CH4 conversion and CO selectivity remained at around 95% while processing a steady output voltage (0.69 V), demonstrating excellent activity and coke/sulfur tolerance that have rarely been reported. This work delivered an efficient way for biogas utilization in the context of efficient energy conversion technologies.

Toward highly efficient in situ dry reforming of H2S contaminated methane in solid oxide fuel cells via incorporating a coke/sulfur resistant bimetallic catalyst layer

The escalating global warming effects are a reason for immediate measures to reduce the level of greenhouse gases. In this context, dry reforming of methane (DRM), an old yet both scientifically and industrially important process, is making a comeback in contributing to the utilization of CO2. However, catalyst deactivation (sulfur poisoning and coke formation) and the associated high energy consumption remain technological hurdles to its practical implementation. Here we demonstrated that dry reforming of H2S-containing CH4 can be efficiently conducted in conventional solid oxide fuel cells via incorporating a coke/sulfur resistant catalyst layer. The add-on layer, composed of tailored Ce0.8Zr0.2O2 supported NiCu nanoclusters, demonstrated outstanding in situ reforming activity while possessing reasonable coke/sulfur resistance. At 800 °C and in a 50 ppm H2S containing CH4–CO2 mixture, the cell had a maximum power density of 1.05 W cm−2, a value high enough for practical application. Through H2 selective oxidation, the energy required for DRM was partially compensated for and the produced water greatly suppressed the carbon deposition. This study offers a new dimension in cogenerating CO2-derived synthesis gas and electrical power in the context of increasing interests in efficient utilization of H2S-containing CH4 and CO2.

A bifunctional solid oxide electrolysis cell for simultaneous CO2 utilization and synthesis gas production

We hereby report on a pioneering and inspiring solid oxide cell which, assisted by natural gas, utilizes a bifunctional electrolysis cell configuration to effectively consume CO2 to produce CO at the cathode side and simultaneously synthesize highly valuable syngas (mixture of CO and H2) at the anode side via a one-step green process.