压力诱导相变原位构建BiVO4/Bi0.6Y0.4VO4型异质结增强光催化全解水性能

光催化完全分解水制氢是一个在粉末颗粒中实现多个串行物理化学步骤的复杂反应过程.这一过程在理论上具有体系简单、成本低、易操作等特点.然而,单步光激发系统中通常存在严重的光生载流子复合,这极大地制约了光催化的整体效率.利用能带结构不同的半导体合理构建异质结催化剂被认为是解决这一难题的重要途径之一.特别是近年来,S型异质结概念的提出为设计异质结结构以及分析不同半导体之间的载流子迁移问题提供了新的思路.本文以小粒径BiVO₄/Bi_0.6Y_0.4VO₄(BYV)为研究对象,首先利用"共沉淀-晶化"的方法制备了BYV固溶体纳米颗粒,随后利用压力诱导固溶体中四方相钒酸铋结构转变为单斜相,从而构建了BiVO₄/Bi_0.6Y_0.4VO₄复合光催化剂.XRD,Raman,HRTEM,HAADF-EDS的结果表明,经过高压后处理的BYV固溶体表面会出现粒径约为5 nm单斜钒酸铋纳米颗粒,实现了原位构建异质结结构.随后载流子动力学的相关表征以及Au选择性光沉积的结果表明,在光照条件下,所构建异质结中的光生电子主要分布在BYV固溶体上,而在表面形成的单斜相钒酸铋颗粒主要起到了类似"空穴"捕获的作用.这种在异质结中的载流子迁移路径符合S型异质结机理.电化学、稳态荧光光谱以及瞬态荧光光谱的表征结果表明,相比于单一固溶体,在S型异质结这种两步激发系统中所存在的载流子迁移路径能够大幅促进光生载流子分离,从而提高了小粒径BYV的光催化完全分解水性能.综上,构建S型异质结是一种解决小粒径光催化剂中载流子分离能力差的有效途径.同时,压力诱导材料晶型转变实现原位构建异质结的制备方法也为提高光生载流子分离效率提供了新的研究思路与机遇.     

太阳能光催化分解水制氢※

利用太阳能光催化分解水制氢是解决能源环境问题并实现太阳能有效转化和储存最有前途的技术之一, 这一“圣杯”式反应经过几十年不懈努力取得了诸多重要研究进展. 本文将综述光催化分解水制氢体系的基本概念、活性测试方法与注意事项、光催化材料种类等; 并从光催化分解水制氢的光吸收、光生电荷分离和表面催化反应等基本过程和关键科学问题的角度总结其重要研究进展, 最后对于太阳能光催化分解水制氢的挑战和潜在的发展方向进行分析和展望. 希望通过本综述的简要介绍能让刚从事光催化分解水制氢研究的青年科技人员清晰地了解掌握该领域的一些基本概念、操作规范、研究总体进展和现状等.     

Ni2P-NiS双助剂促进g-C3N4光催化产氢动力学

本文通过简单的一步水热法得到Ni₂P-NiS双助催化剂,之后采用溶剂蒸发法将Ni₂P-NiS与g-C₃N₄纳米片结合构建获得无贵金属的Ni₂P-NiS/g-C₃N₄异质结。研究结果表明,优化后的复合材料具有良好的光催化产氢活性,其产氢速率最高可到6892.7 μmol·g^-1·h^-1,分别为g-C₃N₄ (150 μmol·g^-1·h^-1)、15%NiS/g-C₃N₄ (914.5 μmol·g^-1·h^-1)和15%Ni₂P/g-C₃N₄ (1565.9 μmol·g^-1·h^-1)的46.1、7.5和4.4倍。这主要归因于Ni₂P-NiS相比Ni₂P和NiS单体具有更好的载流子转移能力,其与g-C₃N₄形成的肖特基势垒能有效促进光生载流子在二者界面上的分离,同时Ni₂P-NiS能进一步降低析氢过电势,进而显著增强了表面析氢反应动力学。本研究为开发稳定、高效的非贵金属产氢助剂提供了实验基础。     

钴铁水滑石基材料在电催化析氧中的应用

析氧反应(OER)是电催化裂解水、二次金属-空气电池和可再生燃料电池等绿色可持续能源储存和转化技术中的关键步骤,但其较高的势垒和迟滞的动力学过程限制了反应的效率。因此,设计开发高效、稳定的非贵金属催化剂是新能源领域面临的挑战之一。钴铁水滑石(CoFe LDH)材料具有独特的二维层状结构、丰富多变的化学组成、高分散的金属阳离子、优异的稳定性和成本低廉等优点,在OER反应中有广泛的应用前景。但不良的导电性和有限的活性位点阻碍了CoFe LDH的工业化应用。本文首先介绍了CoFe LDH的结构并阐述了其OER反应机理,接着总结了CoFe LDH的制备工艺,并详细综述了近年来提升其 OER性能的改性策略:插层剥离、空位制造、材料复合、离子取代和衍生物等。最后讨论了水滑石材料现阶段存在的问题和未来在能源转化和利用领域的发展方向。     

High-entropy transition metal chalcogenides as electrocatalysts for renewable energy conversion

High-entropy transition metal chalcogenides (HE-TMCs) are advantageous in electrocatalytic applications compared to other entropy-stabilized systems owing to the greater orbital extension and energetic match of p-orbitals in chalcogenides with d-orbitals of the transition metals providing additional space to tailor their electronic structure. The high-configurational entropy of HE-TMCs leads to stabilization of cubic rock salt, wurtzite-type and hexagonally packed 2D structures. Due to the multi-element nature of HE-TMCs, the synergy among different elements results in tunable d- and p-band positions. As a consequence, the adsorption energies of electrocatalytic reaction intermediates can be tailored to enhance catalytic performance in water splitting and CO₂ reduction. Furthermore, the entropy-stabilized disordered microstructural state of the material endows HE-TMCs with improved corrosion resistance. Despite recent advances in HE-TMC electrocatalysis, challenges such as identification and synthesis of efficient HE-TMCs as well as the identification of catalytically active sites and reaction mechanisms on HE-TMCs remain to be investigated.     

Defects-engineered tailoring of tri-doped interlinked metal-free bifunctional catalyst with lower gibbs free energy of OER/HER intermediates for overall water splitting

Controllable tailoring of metal-free/carbon-based nanostructures tends an encouraging way to enhance the bifunctional activity of electrodes, but a great challenge owing to the sluggish kinetics of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, a facile tempted-defects assisted fractionation strategy is presented to synthesize N, S, and O tri-doped metal-free catalyst (DE-TDAP). Due to this effective tempted-defects and heteroatoms interlinking in DE-TDAP, it delivers the lowest overpotential toward both the OER (346 mV) and HER (154 mV) at 10 mA cm^?2. Remarkably, the DE-TDAP-electrode carries only a cell voltage of 1.81 V at 10 mA cm^?2 for overall water splitting and long-term stability. Considerably, the density functional theory (DFT) calculation exposes that the tailored-defects in tri-doped interlinking could enhance bifunctional catalytic performance devising from lower Gibbs free energy of OER/HER intermediates on active sites. This struggle henceforth provides a perceptive understanding of the synergetic principles of heteroatom-interlinking-tailoring nanostructures in water splitting.     

Comprehensive and High-throughput Electrolysis of Water and Urea by 3–5 nm Nickel and Copper Coordination Polymers

Metal-organic coordination polymers (CP) have attracted the scientific attention for electrochemical water oxidation as it has the similar coordination structure like natural photosynthetic coordinated complex. However, the harsh synthesis conditions and bulky nature pose a major challenge in the field of catalysis. Herein, 3–5 nm CP particles synthesized at room temperature using aqueous solutions of Ni²⁺/Cu²⁺ and 2,5-dihydroxyterepthalic acid as precursor were applied for alkaline water and urea electrolysis. The overpotential required is only 300 mV at 10 mA cm⁻² by Nano-Ni CP for water oxidation, with turnover frequency (TOF) of 21.4 s⁻¹ which is around 8 times higher than its bulk-counterpart. Overall water and urea splitting were achieved with Nano-Cu (−) ∥ Nano-Ni (+) couple on Ni foam at 1.69 and 1.52 V to achieve 10 mA cm⁻², respectively. High electrochemical surface area (ECSA), high TOF, and enhanced mass diffusion are found to be the key parameters responsible for the state-of-the-art water and urea splitting performances of nano-CPs as compared to their bulk counterparts.     

Transition metal-based electrocatalysts for overall water splitting

Electrochemical overall water splitting is attracting a broad focus as a promising strategy for converting the electrical output of renewable resources into chemical fuels, specifically oxygen and hydrogen. However, the urgent challenge in water electrolysis is to search for low-cost, high-efficiency catalysts based on earth-abundant elements as an alternative to the high-cost but effective noble metal-based catalysts. The transition metal-based catalysts are more appealing than the noble metal catalysts because of its low cost, high performance and long stability. Some recent advances for the development in overall water splitting are reviewed in terms of transition metal-based oxides, carbides, phosphides, sulfides, and hybrids of their mixtures as hybrid bifunctional electrocatalysts. Concentrating on different catalytic mechanisms, recent advances in their structural design, controllable synthesis, mechanistic insight, and performance-enhancing strategies are proposed. The challenges and prospects for the future development of transition metal-based bifunctional electrocatalysts are also addressed.     

PBFC-PI量子动力学方法及应用

对多原子体系的量子动力学计算非常重要, 然而, 对含六原子以上的分子体系进行精确量子动力学计算仍具挑战性. 面向过程的基函数定制(PBFC)-并行迭代(PI)方法是一种高效的量子动力学方法, 已应用于对含九原子的丙二醛异构体系的氢迁移速率的精确量子计算. 本综述首先阐明了PBFC的基本思想, 之后重点回顾了PBFC-PI方法的具体内容、 该方法与其它方法的结合及其应用方面的新进展. 应用这些方法实现了对单氢迁移、 协同双氢迁移和分步双氢迁移3种类型基准体系的大规模并行计算, 有助于获得对氢迁移过程的新认识.     

修饰吡啶衍生物的染料敏化光阳极水氧化性能的研究

染料敏化光电化学电池(DSPECs)是构建人工光合作用体系的潜在方式,其优势在于可通过优化染料结构来拓展可见光吸收范围,从根本上提高太阳能利用效率.染料敏化光阳极在受激发产生电荷分离之后,激发电子注入TiO₂半导体导带,由于其导带位置比传统的可见光半导体,如BiVO4和Fe3O4等相比较负,因此理论上可以在较小的偏压下取得较大的光电转换效率,也更有利于和光阴极相耦合实现无偏压分解水.电荷传输动力学研究表明,注入到TiO₂导带的电子向氧化态光敏剂和催化剂的回传是造成体系能量损失的主要原因,集中体现在光电流密度和效率的降低.目前,已经报道了多种手段来减少DSPECs光阳极表面的电子回传,包括使用带有长烷基链的锚定基团对水氧化催化剂进行修饰,在半导体表面引入电子中介体以及使用核-壳结构的基底等.其中,SnO2/TiO₂基底被广泛应用在染料敏化光阳极中,这种基底可以提高光生电子的注入效率,同时两种金属氧化物之间的异质结有效抑制了电子回传,从而提高了DSPECs的光电活性.然而,核-壳结构基底需要使用原子层沉积技术来制备,所以操作相对复杂.本文基于Ru-bda(bda=2,2'-联吡啶-6,6'-二羧酸)结构的分子水氧化催化剂和带有磷酸修饰基团的三联吡啶钌通过共吸附的方式制备染料敏化光阳极,在不使用核-壳结构基底的情况下,利用吡啶衍生物对TiO₂电极表面的修饰来减少电子回传.本文利用一系列吡啶衍生物作修饰负载在TiO₂光阳极上(TiO₂|RuP,1;RuP=Ru(4,4'-(PO3H2)2-2,2'-联吡啶)(2,2'-联吡啶)2;1=Ru(bda)(L)2,bda=2,2'-联吡啶-6,6'-二羧酸,L=(10-吡啶-4-基氧基)癸基)膦酸.在100 mW/cm2的白光照射下(λ>400 nm),TiO₂|RuP,1,P1(P1=4-羟基吡啶)光阳极在0.4 V(vs.NHE)的外加偏压下获得了1 mA/cm2的光电流密度,其光电流比未修饰吡啶的光阳极增加了42%.同时,其入射光子-电流转化效率在470 nm波长的单色光光照下达到最大,为13.6%.经过吡啶衍生物所修饰的光阳极光电性能和文献中利用核-壳结构基底所制备的类似光阳极性能相当,且光电流密度随吡啶对位取代基供电性能的增强而增大.瞬态吸收光谱和电化学阻抗谱测试表明,吡啶吸附在光阳极上能有效地抑制界面上的电子回传,延长电荷分离寿命,是光电流增加的根本原因,这也表明有机小分子修饰是提高染料敏化光阳极性能的简单、有效的策略.