Tree-Bark-Shaped N-Doped Porous Carbon Anode for Hydrazine Fuel Cells.

Metal-free N-doped porous carbon has great potential as a catalyst for hydrazine oxidation in direct hydrazine fuel cells (DHFCs). However, previous studies have reported only half-cell characterization, and the effect of the pore size distribution has not been intensively investigated. Herein, we report the synthesis of highly active, metal-free N-doped carbon (NDC) by controlling the pore size distribution, and for the first time, the effect of the pore size distribution on the anode performance in a DHFC is investigated. As a result, tree-bark-shaped NDC with meso/macroporous (>10 nm) structures exhibit a remarkable power density of 127.5 mW cm-2 in a DHFC.

A graphitic edge plane rich meso-porous carbon anode for alkaline water electrolysis.

There is growing interest in alkaline water electrolysis as a sustainable approach for producing hydrogen, but developing efficient and inexpensive catalysts for the oxygen evolution reaction, which can limit the operational efficiency of water electrolysis due to its considerable overpotential, is regarded as the most overriding challenge. Therefore, significant progress has been made in developing catalysts with transition metal and carbon materials as alternative catalysts. Here, we prepared cobalt containing carbon nanofibers via a facile route of electrospinning and pyrolysis, and metal leached carbon nanofibers were also prepared by subsequently leaching the metal. Despite metal leaching, the latter ones still show comparable activity and stability with iridium black in alkaline water electrolysis. After detailed physicochemical and electrochemical characterizations, we revealed that graphitic edge plane rich carbon is mainly responsible for the activity of our material rather than embedded metal species. In addition, the metal plays a role in forming the specific carbon structure along with improving graphitization based on the catalytic graphitization. This result indicates the importance of the graphitic edge plane and might be helpful to understand carbon anodes for alkaline water electrolysis.

Alkaline Ammonia Electrolysis on Electrodeposited Platinum for Controllable Hydrogen Production.

Ammonia is beginning to attract a great deal of attention as an alternative energy source carrier, because clean hydrogen can be produced through electrolytic processes without the emission of COx . In this study, we deposited various shapes of Pt catalysts under potentiostatic mode; the electrocatalytic oxidation behavior of ammonia using these catalysts was studied in alkaline media. The electrodeposited Pt was characterized by both qualitative and quantitative analysis. To discover the optimal structure and the effect of ammonia concentration, the bulk pH value, reaction temperature, and applied current of ammonia oxidation were investigated using potential sweep and galvanostatic methods. Finally, ammonia electrolysis was conducted using a zero-gap cell, producing highly pure hydrogen with an energy efficiency over 80 %.

Designing a Highly Active Metal-Free Oxygen Reduction Catalyst in Membrane Electrode Assemblies for Alkaline Fuel Cells: Effects of Pore Size and Doping-Site Position.

To promote the oxygen reduction reaction of metal-free catalysts, the introduction of porous structure is considered as a desirable approach because the structure can enhance mass transport and host many catalytic active sites. However, most of the previous studies reported only half-cell characterization; therefore, studies on membrane electrode assembly (MEA) are still insufficient. Furthermore, the effect of doping-site position in the structure has not been investigated. Here, we report the synthesis of highly active metal-free catalysts in MEAs by controlling pore size and doping-site position. Both influence the accessibility of reactants to doping sites, which affects utilization of doping sites and mass-transport properties. Finally, an N,P-codoped ordered mesoporous carbon with a large pore size and precisely controlled doping-site position showed a remarkable on-set potential and produced 70% of the maximum power density obtained using Pt/C.