A simple and straightforward strategy for synthesis of N,P co-doped porous carbon: an efficient support for Rh nanoparticles for dehydrogenation of ammonia borane and catalytic application

Metal nanoparticles (NPs) deposited on nitrogen (N)- and/or phosphorus (P)-doped porous carbon have been investigated as efficient catalysts for hydrolysis of ammonia borane (AB). However, the one-pot synthesis of N,P co-doped porous carbon using low-cost and readily available sources is still a tremendous challenge. Herein, a novel one-pot methodology is developed to fabricate N and P co-doped porous carbon (ATP-C) using non-precious and easily available adenosine triphosphate (ATP). The process of N and P doping does not need additional N or P sources in the material. Moreover, the entire process did not require chemical activation agents, making it more practical for large-scale applications. The resulting ATP-C supported Rh NPs (Rh/ATP-C) exhibit excellent performance for the catalytic hydrolysis of ammonia borane toward hydrogen generation, with a total turnover frequency (TOF) value of 566 mol H₂ min^-1 (mol Rh)^-1 and activation energy (E _a) of 26.3 kJ mol^-1. The catalytic system has shown an outstanding catalytic cycle life during the recycling tests. This work provides a novel method for the production of high performance carbon material supported metal NP catalysts for practical dehydrogenation applications.

Nanocarbon Catalysts: Recent Understanding Regarding the Active Sites

Although carbon itself acts as a catalyst in various reactions, the classical carbon materials (e.g., activated carbons, carbon aerogels, carbon black, carbon fiber, etc.) usually show low activity, stability, and oxidation resistance. With the recent availability of nanocarbon catalysts, the application of carbon materials in catalysis has gained a renewed momentum. The research is concentrated on tailoring the surface chemistry of nanocarbon materials, since the pristine carbons in general are not active for heterogeneous catalysis. Surface functionalization, doping with heteroatoms, and creating defects are the most used strategies to make efficient catalysts. However, the nature of the catalytic active sites and their role in determining the activity and selectivity is still not well understood. Herein, the types of active sites reported for several mainstream nanocarbons, including carbon nanotubes, graphene-based materials, and 3D porous nanocarbons, are summarized. Knowledge about the active sites will be beneficial for the design and synthesis of nanocarbon catalysts with improved activity, selectivity, and stability.

Efficient Metal-Free Electrocatalysts from N-Doped Carbon Nanomaterials: Mono-Doping and Co-Doping

N-doped carbon nanomaterials have rapidly grown as the most important metal-free catalysts in a wide range of chemical and electrochemical reactions. This current report summarizes the latest advances in N-doped carbon electrocatalysts prepared by N mono-doping and co-doping with other heteroatoms. The structure-performance relationship of these materials is subsequently rationalized and perspectives on developing more efficient and sustainable electrocatalysts from carbon nanomaterials are also suggested.

Improvement of O2 adsorption for α-MnO2 as an oxygen reduction catalyst by Zr4+ doping

Zr4+ doped α-MnO2 nanowires were successfully synthesized by a hydrothermal method. XRD, SEM, TEM and XPS analyses indicated that Mn3+ ions, Mn4+ ions, Mn4+δ ions and Zr4+ ions co-existed in the crystal structure of synthesized Zr4+ doped α-MnO2 nanowires. Zr4+ ions occupied the positions originally belonging to elemental manganese in the crystal structure and resulted in a mutual action between Zr4+ ions and Mn3+ ions. The mutual action made Mn3+ ions tend to lose their electrons and Zr4+ ions tend to get electrons. Cathodic polarization analyses showed that the electrocatalytic activity of α-MnO2 for oxygen reduction reaction (ORR) was remarkably improved by Zr4+ doping and the Zr/Mn molar ratio notably affected the ORR performance of the air electrodes prepared by Zr4+ doped α-MnO2 nanowires. The highest ORR current density of the air electrodes prepared by Zr4+ doped α-MnO2 nanowires in alkaline solution appeared at Zr/Mn molar ratio of 1 : 110, which was 23% higher than those prepared by α-MnO2 nanowires. EIS analyses indicated that the adsorption process of O2 molecules on the surface of the air electrodes prepared by Zr4+ doped α-MnO2 nanowires was the rate-controlling step for ORR. The DFT calculations revealed that the mutual action between Zr4+ and Mn3+ in Zr4+ doped α-MnO2 nanowires enhanced the adsorption process of O2 molecules.