Frontiers in Energy最新文献

Ammonia, with its high hydrogen storage density of 17.7 wt.% (mass fraction), cleanliness, efficiency, and renewability, presents itself as a promising zero-carbon fuel. However, the traditional Haber–Bosch (H–B) process for ammonia synthesis necessitates high temperature and pressure, resulting in over 420 million tons of carbon dioxide emissions annually, and relies on fossil fuel consumption. In contrast, dielectric barrier discharge (DBD) plasma-assisted ammonia synthesis operates at low temperatures and atmospheric pressures, utilizing nitrogen and hydrogen radicals excited by energetic electrons, offering a potential alternative to the H-B process. This method can be effectively coupled with renewable energy sources (such as solar and wind) for environmentally friendly, distributed, and efficient ammonia production. This review delves into a comprehensive analysis of the low-temperature DBD plasma-assisted ammonia synthesis technology at atmospheric pressure, covering the reaction pathway, mechanism, and catalyst system involved in plasma nitrogen fixation. Drawing from current research, it evaluates the economic feasibility of the DBD plasmaassisted ammonia synthesis technology, analyzes existing dilemmas and challenges, and provides insights and recommendations for the future of nonthermal plasma ammonia processes.

Developing efficient anode catalysts for direct ammonia solid oxide fuel cells (NH₃-SOFCs) under intermediate-temperatures is of great importance, in support of hydrogen economy via ammonia utilization. In the present work, the pyrochlore-type La₂Zr_2−xNi_xO_7+δ (LZN_x, x = 0, 0.02, 0.05, 0.08, 0.10) oxides were synthesized as potential anode catalysts of NH₃-SOFCs due to the abundant Frankel defect that contributes to the good conductivity and oxygen ion mobility capacity. The effects of different content of Ni²⁺ doping on the crystal structure, surface morphology, thermal matching with YSZ (Yttria-stabilized zirconia), conductivity, and electrochemical performance of pyrochlore oxides were examined using different characterization techniques. The findings indicate that the LZN_x oxide behaves as an n-type semiconductor and exhibits an excellent high-temperature chemical compatibility and thermal matching with the YSZ electrolyte. Furthermore, LZN_0.05 exhibits the smallest conductive band potential and bandgap, making it have a higher power density as anode material for NH₃-SOFCs compared to other anodes. As a result, the maximum power density of the LZN_0.05-40YSZ composite anode reaches 100.86 mW/cm² at 800 °C, which is 1.8 times greater than that of NiO-based NH₃-SOFCs (56.75 mW/cm²) under identical flow rate and temperature conditions. The extended durability indicates that the NH₃-SOFCs utilizing the LZN_0.05-40YSZ composite anode exhibits a negligible voltage degradation following uninterrupted operation at 800 °C for 100 h.

Solid oxide electrolysis cell (SOEC) is a promising water electrolysis technology that produces hydrogen or syngas through water electrolysis or water and carbon dioxide co-electrolysis. Green hydrogen or syngas can be produced by SOEC with renewable energy. Thus, SOEC has attracted continuous attention in recent years for the urgency of developing environmentally friendly energy sources and achieving carbon neutrality. Focusing on 1276 related articles retrieved from the Web of Science (WoS) database, the historical development of SOECs are depicted from 1983 to 2023 in this paper. The co-occurrence networks of the countries, source journals, and author keywords are generated. Moreover, three main clusters showing different content of the SOEC research are identified and analyzed. Furthermore, the scientometric analysis and the content of the high-cited articles of the research of different topics of SOECs: fuel electrode, air electrode, electrolyte, co-electrolysis, proton-conducting SOECs, and the modeling of SOECs are also presented. The results show that co-electrolysis and proton-conducting SOECs are two popular directions in the study of SOECs. This paper provides a straightforward reference for researchers interested in the field of SOEC research, helping them navigate the landscape of this area of study, locate potential partners, secure funding, discover influential scholars, identify leading countries, and access key research publications.

Bio-oil from biomass pyrolysis cannot directly substitute traditional fuel due to compositional deficiencies. Catalytic hydrodeoxygenation (HDO) is the critical and efficient step to upgrade crude bio-oil to high-quality bio-jet fuel by lowering the oxygen content and increasing the heating value. However, the hydrocracking reaction tends to reduce the liquid yield and increase the gas yield, causing carbon loss and producing hydrocarbons with a short carbon-chain. To obtain high-yield bio-jet fuel, the elucidation of the conversion process of biomass catalytic HDO is important in providing guidance for metal catalyst design and optimization of reaction conditions. Considering the complexity of crude bio-oil, this review aimed to investigate the catalytic HDO pathways with model compounds that present typical bio-oil components. First, it provided a comprehensive summary of the impact of physical and electronic structures of both noble and non-noble metals that include monometallic and bimetallic supported catalysts on regulating the conversion pathways and resulting product selectivity. The subsequent first principle calculations further corroborated reaction pathways of model compounds in atom-level on different catalyst surfaces with the experiments above and illustrated the favored C–O/C=O scission orders thermodynamically and kinetically. Then, it discussed hydrogenation effects of different H-donors (such as hydrogen and methane) and catalysts deactivation for economical and industrial consideration. Based on the descriptions above and recent researches, it also elaborated on catalytic HDO of biomass and bio-oil with multi-functional catalysts. Finally, it presented the challenges and future prospective of biomass catalytic HDO.

Formic acid (FA) is a potential biomass resource of syngas with contents of carbon monoxide (CO, 60 wt.%) and hydrogen (H₂, 4.4 wt.%). Among the technologies for FA conversion, the photoreforming of FA has received widespread attention due to its use of green solar energy conversion technology and mild reaction conditions. Herein, a V–W bimetallic solid solution, V_xW_1−xN_1.5 with efficient co-catalytic properties was first and facilely synthesized. When CdS was used as a photocatalyst, the activity performance of the V_0.1W_0.9N_1.5 system was over 60% higher than that of the W₂N₃ system. The computational simulations and experiments showed the V_0.1W_0.9N_1.5 had great metallic features and large work functions, contributing a faster photo-generated carrier transfer and less recombination, finally facilitating a great performance in cocatalyst for syngas production in photoreforming FA. This work provides an approach to synthesizing novel transition metal nitrides for photocatalysis.