The electrochemical conversion of carbon dioxide (CO₂) into valuable chemicals is a feasible way to mitigate the negative impacts of overmuch CO₂ emissions. Porphyrin-based metal organic frameworks (MOFs) are expected to be used for selective and efficient electrochemical CO₂ reduction (ECR) with porous structure and ordered active sites. Herein, we report the synthesis of a monodispersed and spherical organic/inorganic hybrid Cu-TCPP@Cu₂O electrocatalyst composed of Cu-TCPP (TCPP=tetrakis (4-carboxyphenyl) porphyrin) and Cu₂O, where TCPP plays significant roles in regulating the morphology. In-situ formed Cu during ECR process in combination with Cu-TCPP (Cu-TCPP@Cu) can suppress hydrogen evolution, enrich CO intermediate and promote C-C coupling toward C₂ products. The Cu-TCPP@Cu supported on porous carbon (PC) showed ultrafine Cu nanoclusters on PC, and displayed high ECR activity and selectivity toward C₂ products, with a C₂ faradaic efficiency of 62.3% at -1.0 V versus the reversible hydrogen electrode and a C₂ partial current density of 83.4 mA·cm^-2, which is 7.6 times and 13.1 times those of pure Cu₂O and TCPP, respectively. The morphology and hybrid structure of the catalyst were studied to improve the selectivity of ECR to produce C₂ products, which provides a new idea for the design of high-performance ECR catalyst.

Owing to the merits of high energy density, as well as clean and sustainable properties, hydrogen has been deemed to be a prominent alternative energy to traditional fossil fuels. Electrocatalytic hydrogen evolution reaction (HER) has been considered to be mostly promising for achieving green hydrogen production, and has been widely studied in acidic and alkaline solutions. In particular, HER in alkaline media has high potential to achieve large-scale hydrogen production because of the increased durability of electrode materials. However, for the currently most prominent catalyst Pt, its HER kinetics in an alkaline solution is generally 2-3 orders lower than that occurring in an acidic solution because of the low H⁺ concentration in alkaline electrolytes. Fortunately, construction of heterostructured electrocatalysts has proved to be an efficient strategy for boosting alkaline HER kinetics because of their various structural merits. The synergistic effect is a unique characteristic of heterostructures, which means that one functional active site serves as a promoter for water dissociation and another one takes a charge of moderate hydrogen adsorption, thus synergistically improving HER performance. In addition, each building block of the heterostructures is tunable, providing more flexibility and chances to construct optimal catalysts. Furthermore, due to the presence of Fermi energy difference between the two components at the interface, the electronic structure of each component could possibly be rationally modulated, thus much enhanced HER performance in alkaline electrolyte can be achieved. With a deeper understanding of on nanoscience and rapid development of nanotechnology, more sophisticated alternative designing strategies have been explored for constructing high-performance heterostructured electrocatalysts. This review presents an outline of the latest development of heterostructured catalysts toward alkaline HER and the rational design principles for constructing interfacial heterostructures to accelerate alkaline HER kinetics. The basic reaction pathways of HER in alkaline media are first described, and then emerging efficient strategies to promote alkaline HER kinetics, including synergistic effect, strain effect, electronic interaction, phase engineering, and architecture engineering. Finally, current existing challenges and research opportunities that deserve further investigation are proposed for the consideration of novel heterostructures towards practical applications.

In this work, the long-term stability and degradation mechanism of a direct internal-reforming solid oxide fuel cell stack (IR-SOFC stack) using hydrogen-blended methane steam reforming were investigated. An overall degradation rate of 2.3%·kh^-1 was found after the stack was operated for 3000 hours, indicating a good long-term stability. However, the voltages of the two cells in the stack were increased at the rates of 3.38 mV·kh^-1 and 3.78 mV·kh^-1, while the area specific resistances of the three metal interconnects in the stack were increased to 0.276 Ω·cm², 0.254 Ω·cm² and 0.249 Ω·cm². The degradation of the stack might be caused by segregation of chromium on the surface of metal interconnects and the formation of SrCrO₄ insulating phase in the current collecting layer of the cathode, which result in an increase in the interfacial resistance and a decrease in the stack performance. The long-term performance of a flat-tube IR-SOFC stack could be further improved by suitably coating the metal interconnect surface. This work provides theoretical and experimental guideline for the application of hydrogen-blended methane steam reforming in flat-tube IR-SOFC stacks.