Metal‐Based Nanocatalysts via a Universal Design on Cellular Structure

Abstract

and high catalytic activity, [12] which determine the practical application prospects.There are many methods for directly preparing the NM@C catalysts with controlling particle size and enhancing stability, [13] such as simple pyrolysis, [14] wet chemical methods, [15] and atomic layering deposition. [4,16] However, clear designs on the metal catalysts and carbon supports are still lacking, and their problems also limit the practical application of metal-based nanocatalysts. [17] Therefore, it is urgent to develop simple and effective methods to prepare efficient and stable NM@C catalysts.Inspired by biological structures, a variety of materials utilizing the biological or biomimetic structures are developed. The biological cell wall and cell membrane are natural 2D structures with good ion permeability and exchangeability. Their basic structural units are cellulose, phospholipid bilayers, membrane proteins embedded in bilayers, and sugars and glycolipids bonded to the proteins. Many labile bonds, such as COH, CO, and CN, are included in these structural units. According to these composition and structure, we designed a class of metal nanocatalysts supported on biocarbon by the ion exchange and chemical bond anchoring-in situ carbonization coreduction treatment. During the preparation process, the unstable bonds in the cell wall and the membrane are broken, and a Metal-based nanocatalysts supported on carbon have significant prospect for industry. However, a straightforward method for efficient and stable nanocatalysts still remains extremely challenging. Inspired by the structure and comptosition of cell walls and membranes, an ion chemical bond anchoring, an in situ carbonization coreduction process, is designed to obtain composite catalysts on N-doped 2D carbon (C-N) loaded with various noble and non-noble metals (for example, Pt, Ru, Rh, Pd, Ag, Ir, Au, Co, and Ni) nanocatalysts. These 2 nm particles uniformly and stably bond with the C-N support since the agglomeration and growth are suppressed by anchoring the metal ions on the cell wall and membrane during the carbonization and reduction reactions. The Pt@C-N exhibits excellent catalytic activity and long-term stability for the hydrogen evolution reaction, and the relative overpotential at 100 mA cm −2 is only 77 mV, which is much lower than that of commercial Pt/C and Pt single-atom catalysts reported recently.Metal-based nanocatalysts have an irreplaceable role in energy conversion, [1] chemical production, [2] and automotive exhaust purification. [3] Common metal nanocatalysts include noble metal [4][5][6] or transition metal [7] and alloys, [8] which provide active sites for catalytic reactions. The substrate materials commonly used as supports for metal nanocrystals are oxides, [9] sulfides, [10] and carbon materials, [6,11] which mainly serve to stabilize the catalyst and strengthen charge transfer. Metal-based nanocatalysts using carbon as supports (NM@C) own advantages of low-cost, large specific surface area, good electrical conductivi...

Elucidation of Thermal Degradation Model for Low and High Density Polyethylene by Statistical Parameters

“…The estimate of mean activation energy, through various isoconversional methods with corresponding correlation coefficients for LDPE and HDPE is mentioned in Table 2 and Table 3. The determination of degradation model is carried out through masterplots Z(α) which is calculated theoretically and experimentally by Equations (1) and (2). In these equations f(a) and g(a) correspond to integral and differential form of conversion functions given in Table S2(mentioned in supporting information).…”

“…Energy supply and waste management are two critical issues faced by most of the developing economies. The increasing energy demand and improved efficiency of energy conversion process are mainly attributed to technological advancement in present decade, which is anticipated to continue as part of improvement in the living standards [1] [2] . Management of municipal waste streams depends to a large extent on the collection, transport and treatment of waste where unscientific disposal can affect environment and human health [3] .…”

Construction of 2D‐ZnS@ZnO Z‐Scheme Heterostructured Nanosheets with a Highly Ordered ZnO Core and Disordered ZnS Shell for Enhancing Photocatalytic Hydrogen Evolution

“…The surface atoms can be easily exchanged by other ions and vacancies are easily produced in 2D materials because the exposed atoms on the surface have high reactivity and have a significant effect on the physicochemical properties of the material. [28][29]30] Importantly, the highly ordered crystal favors the transfer excited charge carriers and disordered crystal promotes the separation of charge carriers. Therefore, the ZnS@ZnO nanosheet heterostructure with highly ordered ZnO core and disordered ZnS shell could have a high photocatalytic activity.…”

“…Therefore, introduction of vacancies to heterostructured 2D‐ZnS@ZnO photocatalysts can further improve the photocatalytic performance. The surface atoms can be easily exchanged by other ions and vacancies are easily produced in 2D materials because the exposed atoms on the surface have high reactivity and have a significant effect on the physicochemical properties of the material . Importantly, the highly ordered crystal favors the transfer excited charge carriers and disordered crystal promotes the separation of charge carriers.…”

Shape‐stabilized phase change material with enhanced thermal conductivity fabricated based on biomimetic polymerization and in situ reduction of Cu ions

“…[18][19] Toincrease the thermal conductivity of OPCMs, various strategies were reported for the synthesis of shapestabilized phase change materials (ss-PCMs) through immobilizing pristine PCMs into carriers, and in the same time, high thermal conductivity additiveswere introduced into thess-PCMs to enhancetheir thermal conductivity. 20 Many additives, such as metal nanoparticles, 20,21 metal foam, 22 graphite, 23 and carbon nanotubes, [24][25] exhibited significant effects in improving the thermal conductivities of ss-PCMs. Sari et al utilized carbon nanotubes (CNTs) as high-thermal conductive additives in the ss-PCM ofsilica fume/capric acid-palmitic acid (SF/[CA-PA]), and thestudyresults suggested that the thermal conductivity of SF/(CA-PA) was 0.47 W/(mÁK), which was 1.56 times higher than that of the SF/(CA-PA).…”