Influence of Fe_(2)O_(3) on Release Mechanism of NH_(3) and Other Nitrogen-Containing Compounds from Pyrolysis of Three Typical Amino Acids in Urban Sludge

To elucidate the effects of Fe_(2)O_(3) on nitrogen transformation during sludge pyrolysis,thermogravimetry coupled with mass spectrometry(TG-MS)was used to investigate the influences of Fe_(2)O_(3) on the pyrolysis characteristics and the release of important gaseous NO_(x) precursors such as HCN and NH_(3) during pyrolysis of three typical amino acids in urban sludge.The results show that after Fe_(2)O_(3) addition,the total weight loss rate of the three amino acids and the initial decomposition temperature of proline are reduced.The release amounts of NH_(3),HCN,CH_(3)CN,and HNCO from these three representative amino acids—glumatic,arginine,and proline,decrease in the order of arginine,glutamic,proline.The generation of Fe-N complexes,reduces the generation of NH_(3),HCN,CH_(3)CN,and HNCO while the catalysis effects of Fe_(2)O_(3) on the formation of H and H2 play a promoting role in the generation of NH_(3),HCN,CH_(3)CN,and HNCO.The results would provide an experimental and theoretical basis for subsequent research on the NOx precursor formation mechanisms during pyrolysis or combustion of Fe-containing sludge or sludge with additives containing Fe.

Heptanuclear brucite disk with cyanide bridges in a cocrystal and tracking its pyrolysis to an efficient oxygen evolution electrode

The development of efficient oxygen evolution reaction(OER)catalysts is still lacking in exploration of the mechanism of controlled pyrolysis of precursors among new material platforms.Here,a novel Co-based coordination molecular cluster has been first introduced as precursor to obtain metallic cobalt core shelled by N-doped carbon(Co@NC)structure which operates as an oxygen evolution electrode.Specifically,a new cocrystal compound,[Co7II(l3-CN)6(mmimp)6][CoIICl3N(CN)2]á3CH3OH(Co7+1,mmimp=2-methoxy-6-((methylimino)-methyl)phenol),was isolated consisting of Brucite disks of cobalt where the usual bridging l3-OH is replaced by l3-CN produced by the in-situ decomposition of dicyanamide(NC-N-CNà).The cobalt atoms are bonded through the nitrogen atom of the cyanide.Remarkably,time dependent thermogravimetric-mass spectrometry(TG-MS)analysis was utilized to track its pyrolysis process.It allowed us to propose a possible formation process of the Co@NC structure from Co7+1.Interestingly,an extremely superior OER electrode is optimized for Co@NC-600 having the lowest overpotential of257 m V at 10 m A/cm2in 1 mol/L KOH solution.The present study pins down the importance of clusters of transition metals on realizing distinct nanostructures operating as highly efficient OER electrocatalyst.

In-situ evolution process understanding from a salan-ligated manganese cluster to supercapacitive application

The goal of material chemistry is to study the relationship among hierarchical structure,chemical reaction and precision preparation for materials,yet tracking pyrolysis process on multi-dimensional scale is still at primary stage.Here we propose packing mode analysis to understand evolution process in high temperature reaction.As a proof of concept,we first design a salan-ligated Mn3(Mn3(3-MeOsalophen)_(2)(Cl)_(2))cluster and pyrolyze it under an inert atmosphere directly to a mixed valence MnOx embedded in a porous N-doped carbon skeleton(MnOx/C).Meanwhile,combining thermogravimetry-mass spectrometry(TG-MS)with other characterization techniques,its pyrolysis process is precisely tracked real-time and Mn^(2+)/Mn^(3+)ratios in the resulting materials are deduced,ensuring excellent electrochemical advantages.As a result,the as-preferred MnOVC-900 sample reaches 943 F/g at 1 A/g,maintaining good durability under 5,000 cycles with 90%retention.The highlight of packing mode analysis strategy in this work would provide a favorable approach to explore the potential relationship between structure and performance in the future.