煤系黄铁矿表面碳原子掺杂浓度对其疏水性影响的量子化学研究

煤系黄铁矿因碳原子掺杂而增强了表面疏水性。为了脱除煤中黄铁矿,分析煤系黄铁矿表面碳原子掺杂的浓度与其疏水性关系及其机理具有非常重要的意义。采用密度泛函理论和平面波赝势方法计算、模拟了碳原子掺杂的浓度对煤系黄铁矿表面疏水性的影响。结果表明:与理想黄铁矿表面相比,水分子(H_2O)在碳原子掺杂的煤系黄铁矿表面吸附强度减弱;随着碳原子掺杂浓度的升高,吸附强度逐渐减弱,水分子吸附后形成的Fe—O键布居值减小,S—H键变为C—H键且布居值减小,同时表面成键原子间的电荷密度重叠度降低,说明Fe—O、S—H/C—H键的键强减弱,即碳原子掺杂处的黄铁矿表面的亲水性逐渐减弱,在煤泥浮选过程中易浮。最后,从量子化学的角度揭示了碳原子掺杂浓度对煤系黄铁矿表面疏水性的影响机理。

The effect of the carbon components on the performance of carbonbased transition metal electrocatalysts for the hydrogen evolution reaction

The hydrogen evolution reaction(HER)is a promising way to produce hydrogen,and the use of non-precious metals with an excellent electrochemical performance is vital for this.Carbon-based transition metal catalysts have high activity and stability,which are important in reducing the cost of hydrogen production and promoting the development of the hydrogen production industry.However,there is a lack of discussion regarding the effect of carbon components on the performance of these electrocatalysts.This review of the literature discusses the choice of the carbon components in these catalysts and their impact on catalytic performance,including electronic structure control by heteroatom doping,morphology adjustment,and the influence of self-supporting materials.It not only analyzes the progress in HER,but also provides guidance for synthesizing high-performance carbon-based transition metal catalysts.

Pinpointing single metal atom anchoring sites in carbon for oxygen reduction: Doping sites or defects?

Enabling the conversion of chemical energy of fuels directly into electricity without combustion,fuel cells are arousing great interest in both academia and industry.A typical case is the proton exchange membrane fuel cell(PEMFC),already commercialized by automobile giants.For mass popularization,however,three major criteria must be balanced:performance,durability and cost.The electrocatalysts used in both the anode and cathode are the kernel of PEMFCs,being essential for efficient operation.First in the firing‐line is the oxygen reduction reaction(ORR)at the cathode,which is normally very sluggish:over six orders of magnitude slower than the anode hydrogen oxidation reaction(HOR)[1].Thus,considerable efforts have been made to improve the cathode ORR.Identifying the main active sites is key to the design of optimum materials for enhanced ORR.Considering the complex balance of preparation,performance and cost,the active sites of metal‐nitrogen‐carbon(M‐N‐C)catalysts are particularly promising.Coupled with the single metal atom(SMA)catalysts[2–5],two excellent M‐N‐C catalysts were recently reported[6,7].New insights were thereby gained into the delicate architecture of carbon‐based SMA catalysts for ORR.

Ionic-liquid-assisted synthesis of metal single-atom catalysts for benzene oxidation to phenol

Ionic liquids(ILs)have the advantages of low cost,eco-friendliness,abundant heteroatoms,excellent solubility,and coordinated ability with metal ions.These features make ILs a suitable precursor for fabricating metal singleatom catalysts(SACs).Herein,we prepared various metal single atoms anchored on ultrathin N-doped nanosheets(denoted as Cu_(1)/NC,Fe_(1)/NC,Co_(1)/NC,Ni_(1)/NC,and Pd_(1)/NC)by direct pyrolysis using ILs and g-C_(3)N_(4)nanosheets as templates.Taking benzene oxidation to phenol with H_(2)O_(2)as a model reaction to evaluate their catalytic performance and potential applications,Cu_(1)/NC calcined at 1000℃(denoted as Cu1/NC-1000)exhibits the highest activity with a turnover frequency of about 200 h^(-1)in the first 1 h at 60℃,which is better than that of most metal SACs reported in the literature.High benzene conversion of 82% with high phenol selectivity of 96% and excellent recyclability were achieved using the Cu_(1)/NC-1000 catalyst.This study provides an efficient general strategy for fabricating SACs using ILs for catalytic applications.

Dyeing bacterial cellulose pellicles for energetic heteroatom doped carbon nanofiber aerogels

The energy crisis and environmental pollution are serious challenges that humanity will face for the long-term. Despite tremendous efforts, the development of environmentally friendly methods to fabricate new energy materials is still challenging. Here we report, for the first time, a new strategy to fabricate various doped carbon nanofiber （CNF） aerogels by pyrolysis of bacterial cellulose （BC） pellicles which had adsorbed or were dyed with different toxic organic dyes. The proposed strategy makes it possible to remove the toxic dyes from waste-water and then synthesize doped CNF aerogels using the dyed BC pellicles as precursors. Compared with other reported processes for preparing heteroatom doped carbon （HDC） nanomaterials, the present synthetic method has some significant advantages, such as being green, general, low-cost and easily scalable. Moreover, the as-prepared doped CNF aerogels exhibit great potential as electrocatalysts for the oxygen reduction reaction （ORR） and as electrode materials for supercapacitors.