Gold/monolayer graphitic carbon nitride plasmonic photocatalyst for ultrafast electron transfer in solar-to-hydrogen energy conversion

Gold (Au) plasmonic nanoparticles were grown evenly on monolayer graphitic carbon nitride (g-C₃N₄) nanosheets via a facile oil-bath method. The photocatalytic activity of the Au/monolayer g-C₃N₄ composites under visible light was evaluated by photocatalytic hydrogen evolution and environmental treatment. All of the Au/monolayer g-C₃N₄ composites showed better photocatalytic performance than that of monolayer g-C₃N₄ and the 1% Au/monolayer g-C₃N₄ composite displayed the highest photocatalytic hydrogen evolution rate of the samples. The remarkable photocatalytic activity was attributed largely to the successful introduction of Au plasmonic nanoparticles, which led to the surface plasmon resonance (SPR) effect. The SPR effect enhanced the efficiency of light harvesting and induced an efficient hot electron transfer process. The hot electrons were injected from the Au plasmonic nanoparticles into the conduction band of monolayer g-C₃N₄. Thus, the Au/monolayer g-C₃N₄ composites possessed higher migration and separation efficiencies and lower recombination probability of photogenerated electron-hole pairs than those of monolayer g-C₃N₄. A photocatalytic mechanism for the composites was also proposed.     

Vertex-transitive self-complementary uniform hypergraphs of prime order

For an integer n and a prime p, let . In this paper, we present a construction for vertex-transitive self-complementary k-uniform hypergraphs of order n for each integer n such that for every prime p, where ?=max{k₍₂₎,(k−1)₍₂₎}, and consequently we prove that the necessary conditions on the order of vertex-transitive self-complementary uniform hypergraphs of rank k=2^? or k=2^?+1 due to Potoňick and Šajna are sufficient. In addition, we use Burnside’s characterization of transitive groups of prime degree to characterize the structure of vertex-transitive self-complementary k-hypergraphs which have prime order p in the case where k=2^? or k=2^?+1 and , and we present an algorithm to generate all of these structures. We obtain a bound on the number of distinct vertex-transitive self-complementary graphs of prime order , up to isomorphism.     

Variational-Like Inequalities with Generalized Monotone Mappings in Banach Spaces

In this paper, we introduce two classes of variational-like inequalities with generalized monotone mappings in Banach spaces. Using the KKM technique, we obtain the existence of solutions for variational-like inequalities with relaxed 511nk16051x35/xxlarge951.gif" alt="eegr" align="MIDDLE" BORDER="0">–511nk16051x35/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"> monotone mappings in reflexive Banach spaces. We present also the solvability of variational-like inequalities with relaxed 511nk16051x35/xxlarge951.gif" alt="eegr" align="MIDDLE" BORDER="0">–511nk16051x35/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"> semimonotone mappings in arbitrary Banach spaces by means of the Kakutani-Fan-Glicksberg fixed-point theorem. The results presented in this paper extend and improve the corresponding results of Refs. 1–6.     

加氢裂化预处理催化剂的发展

讨论了雪佛龙技术转让部的加氢裂化预处理催化剂的发展历史.用"更多的类型Ⅱ活性位导致更好的HDN/HDS催化性能"理论解释了我们最近研发的加氢裂化预处理催化剂HDN催化性能好的原因.     

C-I共掺杂多孔g-C3N4光催化分解水制氢

氢气是一种可替代传统燃料的理想清洁能源,利用光催化技术分解水制氢是制取氢气的有效途径之一.无机半导体光催化材料具有较高的活性和稳定性,且原料丰富,易加工改性.目前针对光催化技术的应用,大量的研究工作都集中在开发可见光响应光催化剂,以提高对可见光的利用率.同时,非金属聚合物半导体因其特殊的光电性质,在光催化应用研究中越来越受到关注,如庚嗪基微孔聚合物(HMP)和共价三嗪基骨架(CTF).石墨相碳化氮(g-C3N4)是一种典型非金属二维聚合物半导体,被认为是一种非常有价值的光催化材料.然而,其较低的光生电子的传输效率限制了其实际应用,因此诸多研究对g-C3N4的物理化学结构进行优化,如半导体耦合、共聚合、纳米结构设计和掺杂.非金属掺杂是一种有效的方法,由于原子电负性差异引起的电荷分离可有效改善载流子传输效率,且保持半导体的非金属性质.通过O,B,P和S等掺杂可以扩大可见光响应范围,并调节能带位置以改善光催化活性.除了常见的单一非金属掺杂,金属和非金属元素或多非金属元素共掺杂的办法同样可提高g-C3N4的光催化性能.本工作通过两步法对双氰胺、尿素和碘化1-乙基-3-甲基咪唑的混合物直接热聚合,合成C-I共掺杂的多孔g-C3N4,其在可见光照射下表现出较高的产氢活性和稳定性.采用X射线衍射(XRD)、X射线光电子能谱(XPS)、荧光光谱(PL)和电化学实验等方法对多孔掺杂g-C3N4结构进行详细表征和分析.在助催化剂Pt和电子牺牲剂(三乙醇胺)存在的条件下,采用可见光(>400 nm)照射分解水产氢的方法评价其光催化活性.结果表明,后热处理和碘离子液掺杂对g-C3N4材料的结构和性能具有较大影响.C-I共掺杂和后热处理使催化剂产物颗粒尺寸减小,形成多孔片层状紧密堆积,比表面积和孔隙率显著增加,吸收带边发生蓝移.后热处理使样品层间距减小,聚合度增加,有利于电荷传输,C-I共掺杂后出现更多的缺陷,但没有改变其层状堆积的特性.XPS结果表明,样品中碘元素以I-和I5+的形式存在,改性后催化剂C/N比明显增加,sp2芳环N含量增加,表面氨基含量降低,表明后热处理和C-I共掺杂没有改变多孔g-C3N4的基本骨架,共轭结构更加完善.PL和光电流结果表明,改性后样品的PL强度均显著降低,并且随着掺杂量的增加而逐渐降低,表明共掺杂可抑制光生电荷的复合.电化学测试结果表明,后热处理和C-I共掺杂的样品界面电荷转移电阻降低,导电率和电荷迁移率增加,从而有助于提高光催化性能.光解水产氢性能测试表明,后热处理和C-I共掺杂有利于催化剂产氢速率的提高,改性后CNIN0.2的产氢速率达168.2μmol/h,是纯氮化碳的9.8倍.经过多次循环测试,其产氢性能保持稳定而没有显著下降,表明其产氢稳定性较好.