锌镉硫量子点增强的光催化产氢活性

光催化分解水产氢是利用太阳能解决当今能源危机和环境污染问题的理想策略.硫化镉光催化剂由于具有较窄的带隙、有效的光吸收能力、较负的导带位置和较强的还原能力等而受到广泛关注.然而,硫化镉光催化剂的光生电子-空穴复合速率高,导致其光催化活性比较低,因此在光催化领域的应用受到限制.为此,人们采取了很多方法来改善硫化镉光催化剂的光催化性能,例如加入助催化剂、构建异质结、表面修饰以及形成固溶体光催化剂等.合成固溶体光催化剂被认为是提高硫化镉光催化活性最具有发展前景的方法之一,固溶体光催化剂通过形成轨道杂化而表现出可控的带隙和带边位置.在固溶体光催化剂中,锌镉硫胶体量子点引起了很多关注.锌镉硫胶体量子点的颗粒尺寸较小,这就使得光生电子和空穴由催化剂内部转移到表面的距离较短,增大了载流子分离效率.另外,锌镉硫胶体量子点具有较负的导带位置、可调控的带隙、较好的水中分散性以及良好的光吸收等优点,因此锌镉硫胶体量子点从其他光催化剂中脱颖而出.本文分别采用热注法和传统共沉淀法制备了油溶性锌镉硫量子点和水溶性锌镉硫纳米颗粒.发现油溶性量子点亲水性能较差,几乎没有光催化活性,但油溶性量子点易通过配体交换过程转换成水溶性量子点,无机硫作为锌镉硫量子点的表面水溶性配体,可使量子点具有较好的亲水性.通过电化学测试、稳态荧光以及时间分辨荧光测试结果表明,相比于锌镉硫纳米颗粒,水溶性锌镉硫量子点具有更高的电子空穴分离效率.光催化产氢测试发现,在牺牲剂甘油存在的条件下,水溶性锌镉硫量子点的光催化产氢速率(1220μmol g^?1 h^?1)显著提高,约是锌镉硫纳米颗粒产氢速率的10倍.加入助催化剂Ni^2+后,锌镉硫量子点表现出最高的光催化产氢活性(2253μmol g^?1 h^?1),在420 nm灯的光照条件下,表观量子效率达到15.9%.光催化活性的增大主要归因于量子点较小的颗粒尺寸、表面无机硫配体以及助催化剂的添加,这些都有利于载流子的快速分离和转移,降低其复合,延长其寿命,并且加速了产氢动力学,因此提高了水溶性锌镉硫量子点的光催化产氢活性.     

生物分子辅助低成本制备Zn0.9Cd0.1S固溶体及其高效可见光光催化制氢

如何提高光催化制氢量子产率是太阳能分解水制氢研究的重点和焦点. Zn-Cd-S固溶体因具有窄的带隙宽度及合适的导带和价带位置而显示了广阔的应用前景. 然而, 两方面的问题限制了其规模化应用: (1)往往需负载Pt, Pd, Ru和Rh等贵金属助催化剂才能获得可观的光催化性能; (2)传统合成技术通常采用硫代乙酰胺、硫脲及硫化钠等昂贵且有毒的化学试剂作硫源. 与上述硫源相比, 生物小分子L-胱氨酸分子中含有-COOH、-NH2及-SH基团, 这些基团易于与金属阳离子配位, 因此能够有效调控硫源释放S2-的速度, 硫化物的形貌、尺寸以及取向能够灵活地得到调控. 另外, 在强碱或强酸性介质中, L-胱氨酸具有良好的水溶性, 因此材料的合成可选择在水介质中, 这对光催化过程是非常关键的, 有利于改善材料在光催化反应过程中的稳定性. 基于此, 本文以经济环保的生物小分子作硫源, 制备了高效、稳定且有可见光响应的纳米硫化物光催化体系, 旨在发展环境友好、条件温和、成本低廉、操作简单和易于工业化生产的绿色制备技术, .以L-胱氨酸为硫源和结构导向剂, 采用水热合成技术在温和条件下制备了立方相结构的Zn-Cd-S固溶体光催化剂, 采用XRD, TEM, HRTEM, XPS, UV-vis及N2吸附等手段表征了其结构和形貌. 结果表明, 随Zn含量增加, 其带隙在2.11-3.19 eV间连续可调. 在可见光(λ > 420 nm)照射、无助催化剂和Na2S/Na2SO3水溶液为牺牲剂的条件下研究了其光催化制氢的性能. 其中Zn0.9Cd0.1S具有最佳的光催化活性, 其产氢速率约为4.4 mmol h -1g -1(无助催化剂, 远高于CdS), 且显示优良的稳定性及抗光腐蚀能力. 通过经验公式计算得出了其能带结构示意图, 结果表明, ZnxCd1-xS固溶体的导带和价带的位置随着Zn含量的增加而向更负的导带和更正的价带移动. 固溶体导带电位更负促进更有效的氢产生, 电位价带更正导致电荷更容易发生转移. Zn0.9Cd0.1S高的光催化活性可能归因于中等的导带边缘和最合适的带隙. 最后利用光电流及交流阻抗阐明了其光生电子-空穴对的分离及迁移机理. 与CdS相比, Zn-Cd-S固溶体的形成促进了光生载流子在界面间的传输, 抑制了其快速复合, 从而大幅度改善了光催化活性及稳定性. 该硫化物纳米晶的绿色制备技术期望可推广到其它硫化物可见光光催化体系.     

生物分子辅助低成本制备Zn_(0.9)Cd_(0.1)S固溶体及其高效可见光光催化制氢（英文）

如何提高光催化制氢量子产率是太阳能分解水制氢研究的重点和焦点.Zn-Cd-S固溶体因具有窄的带隙宽度及合适的导带和价带位置而显示了广阔的应用前景.然而,两方面的问题限制了其规模化应用:(1)往往需负载Pt,Pd,Ru和Rh等贵金属助催化剂才能获得可观的光催化性能;(2)传统合成技术通常采用硫代乙酰胺、硫脲及硫化钠等昂贵且有毒的化学试剂作硫源.与上述硫源相比,生物小分子L-胱氨酸分子中含有-COOH、-NH_2及-SH基团,这些基团易于与金属阳离子配位,因此能够有效调控硫源释放S~(2-)的速度,硫化物的形貌、尺寸以及取向能够灵活地得到调控.另外,在强碱或强酸性介质中,L-胱氨酸具有良好的水溶性,因此材料的合成可选择在水介质中,这对光催化过程是非常关键的,有利于改善材料在光催化反应过程中的稳定性.基于此,本文以经济环保的生物小分子作硫源,制备了高效、稳定且有可见光响应的纳米硫化物光催化体系,旨在发展环境友好、条件温和、成本低廉、操作简单和易于工业化生产的绿色制备技术,.以L-胱氨酸为硫源和结构导向剂,采用水热合成技术在温和条件下制备了立方相结构的Zn-Cd-S固溶体光催化剂,采用XRD,TEM,HRTEM,XPS,UV-vis及N2吸附等手段表征了其结构和形貌.结果表明,随Zn含量增加,其带隙在2.11–3.19e V间连续可调.在可见光(λ420 nm)照射、无助催化剂和Na2S/Na_2SO_3水溶液为牺牲剂的条件下研究了其光催化制氢的性能.其中Zn_(0.9)Cd_(0.1)S具有最佳的光催化活性,其产氢速率约为4.4 mmol h~(-1)g~(-1)(无助催化剂,远高于CdS),且显示优良的稳定性及抗光腐蚀能力.通过经验公式计算得出了其能带结构示意图,结果表明,Zn _x Cd_(1-x) S固溶体的导带和价带的位置随着Zn含量的增加而向更负的导带和更正的价带移动.固溶体导带电位更负促进更有效的氢产生,电位价带更正导致电荷更容易发生转移.Zn_(0.9)Cd_(0.1)S高的光催化活性可能归因于中等的导带边缘和最合适的带隙.最后利用光电流及交流阻抗阐明了其光生电子-空穴对的分离及迁移机理.与CdS相比,Zn-Cd-S固溶体的形成促进了光生载流子在界面间的传输,抑制了其快速复合,从而大幅度改善了光催化活性及稳定性.该硫化物纳米晶的绿色制备技术期望可推广到其它硫化物可见光光催化体系.     

单层MoS2在合金化及应力调控下光催化裂解水产氢的理论研究

基于密度泛函的第一性能原理计算方法研究了单层MoS_2分别与MoSe_2、MoTe_2、WS_2进行合金化,以及加入2%应力条件下,对光催化裂解水性能的影响。计算结果表明,单层MoS_2通过与MoSe_2、MoTe_2、MoWS_2进行合金化,并施加压应力两种手段进行调控,可使带隙变大的同时,提高CBM(conduction band minimum)带边位置,从而提高光催化分解水的效率。通过能带和态密度的计算表明,合金元素原子形成的不是孤立能级而是能带,对载流子寿命影响小。     

固溶体内电场调控增强Bi24O31ClxBr10-x体相电荷流动和光催化活性

光催化是一种在能源和环境领域有着重要应用前景的绿色技术,在光照射下可将有机污染物彻底降解为二氧化碳和水,但因缺乏精确调控电荷流动的方法,导致大多数光催化剂活性不高.因此,促进光生电荷的高效分离一直是光催化研究的重要方向.目前多数电荷分离调控研究集中于表面修饰、表面缺陷设计、异质结构建等表面电荷分离改善策略,而对于体相电荷分离调控研究相对较少.卤氧化铋固溶体光催化材料由于独特的层状晶体结构、可调节的带隙结构和优化的电荷分离效率,近年来受到广泛关注.目前对固溶体的体相电荷分离机理尚不清楚.内电场作为一种新的增强光催化反应活性的有效调控途径,通过定向促进体相电荷的分离和转移,使光生载流子快速参与氧化还原反应.然而,通过调控内电场来增强卤氧化铋固溶体光催化活性的报道较少,且缺乏从理论和实验的角度对固溶体内电场大小以及电荷分离机理的分析.本文构建了具有相同形貌和晶体结构的Bi₂₄O₃₁Cl_xBr_10-x固溶体光催化剂,并考察了其催化性能.密度泛函理论计算、开尔文探针力显微镜(KPFM)和Zeta电位测试结果表明,通过改变卤素类型和比例可增加晶体结构单元的不对称性,从而调节[Bi₂₄O₃₁]和[X]层之间的电势差,增强光催化材料的内电场强度,促进体相电荷分离和转移效率,进而提高酚类有机污染物的降解活性.光电化学测试发现,相较于Bi₂₄O₃₁Cl₁₀和Bi₂₄O₃₁Br₁₀,Bi₂₄O₃₁Cl₄Br₆固溶体体相电荷分离效率显著提高,表面和界面上的电荷转移效率以及载流子密度增加.Bi₂₄O₃₁Cl₄Br₆的载流子密度分别是Bi₂₄O₃₁Cl₁₀和Bi₂₄O₃₁Br₁₀的33.1倍和4.7倍,Bi₂₄O₃₁Cl₄Br₆固溶体降解双酚A活性分别是Bi₂₄O₃₁Cl₁₀和Bi₂₄O₃₁Br₁₀的6.21倍和2.71倍.此外,其它酚类的降解实验也证明了光催化活性和内电场强度以及电荷分离效率成正相关.综上所述,本文从内电场的角度揭示了固溶体策略对光催化性能增强的内在机理,这些发现将进一步加深对体相电荷运动行为的理解,为设计高活性光催化剂提供一条新的途径.     

内电场与光催化性能调控

光生载流子的高效分离是提升光催化反应效率的重要步骤.近年来,内电场作为提高载流子分离效率的内在驱动力而成为光催化材料研究领域的热点之一.本文综述了国内外通过内电场调控光催化性能的研究动态和主要成果.内电场不仅是电子和空穴分离的内在驱动力,而且影响半导体材料费米能级的变化及载流子浓度分布,进而调控了光催化材料导带和价带的弯曲程度及载流子迁移路径.光催化材料内电场的产生机制主要有铁电材料极化、p-n异质结/多晶结、极化表面、晶面间及非线性光学材料内电场等方式,这些方式有效地提高了光生载流子的分离效率,降低电子和空穴复合的几率,从而进一步提高其光催化性能.最后,本文对构建内电场的未来发展趋势进行了展望,并强调了利用先进物理技术并结合理论计算方法来表征内电场的分布及作用的重要性.     

固溶体Bi_2Mo_(1-x)W_xO_6的水热合成及光催化性能

采用水热法,在较低温度下合成了系列Bi2Mo1-xWxO6固溶体。结果表明,W的替代抑制了固溶体的晶粒生长,导致了较小的晶粒尺寸。随着x的增加,红外光谱中840cm-1处M-O键的振动频率νM-O有规律地向低频率方向移动,表明Mo6+离子逐步被W6+替代,生成了无限互溶的固溶体。光吸收性能研究表明,随着W6+逐步替代Mo6+,带隙出现了先降后升的趋势,x=0.4时带隙最小。而固溶体的光催化性能随着x的增加,出现了先增后减的趋势,x=0.4时光催化活性最高。此外,含W样品的光催化活性高于Bi2MoO6。这与固溶体的带隙、带结构和晶粒尺寸变化有关。     

纳米TiO_(2)光催化抗菌应用的研究进展北大核心CSCD

光催化纳米TiO_(2)以其出色的光催化、化学稳定性以及广谱抗菌性受到科研人员的青睐。然而,其存在的一些问题,如宽带隙、高过电位和光生载流子快速复合等限制了其光催化性能。本文综述了近年来TiO_(2)光催化在抗菌方面的研究进展。对纳米TiO_(2)光催化抗菌作用机理进行了探讨,并讨论了提高TiO_(2)光催化抗菌活性的几种策略,包括进行纳米TiO_(2)结构设计、光的调控、掺杂金属离子、掺杂非金属离子、贵金属修饰和偶联其他材料。改性TiO_(2)光催化剂显著抑制了细菌细胞的生长,在生物医学工程领域具有独特的应用前景。     

无机-有机杂化光催化剂:合成、机理及应用（英文）

由无机与有机组分组成的无机-有机杂化材料因其优异的性能及良好的物理化学性质在光催化领域得到了广泛的关注.目前,已经开发的单相光催化剂有很多种,但其很难同时满足宽的光激发范围以及高的光吸收能力和强的氧化还原能力等需求,因此,科研人员开发了很多方法去解决上述问题,主要包括以下两大类.第一类,修饰光催化剂扩大光激发范围以及增强可见光吸收.例如构建固溶体、引入表面缺陷、杂质掺杂、染料敏化和表面等离子体共振等策略.第二类,构建半导体异质结,通过界面处的协同作用有效促进光生电子空穴对的转移与分离.例如type II型、直接Z型以及S型异质结等.有机成分与无机成分的杂化是有效解决上述问题的方法之一.大部分有机材料具有成本低、吸光系数高以及比表面积大等优点;但低的强度以及宽的带隙限制了有机材料在光催化上的应用.而大部分无机材料具有高强度、窄带隙以及良好的光学性能.但低韧性和较差的分散性限制了无机材料在光催化上的应用.无机-有机杂化材料不仅保留了无机与有机组分的原有性质,而且界面处组分之间的协同作用会产生新的性质,如高的载流子传输能力和高的光吸收能力等.无机-有机杂化材料是多相材料,其中的一相是纳米材料...     

用于改进H2O2制备的1D/0D异质结的ZnIn2S4@ZnO S型光催化剂(英文)

过氧化氢作为一种绿色氧化剂,被广泛应用于食品工业、有机合成、医疗消毒和污水处理等领域.目前,大多数用于工业生产的过氧化氢是通过蒽醌法制备.传统的蒽醌法能耗高、有机副产物多、环境污染严重,因此,利用清洁的太阳能进行半导体光催化生产过氧化氢备受关注.其中,ZnO半导体因其高稳定性、无毒性、良好的生物相容性和合适的导带位置而成为一种潜在的过氧化氢生产材料.然而,单一的ZnO在光催化生产过氧化氢中面临着许多问题,如载流子分离效率低、可见光吸收弱等,从而导致其较低的光催化性能.因此,多种策略被用于解决上述问题,如掺杂非贵金属元素、晶面调控和异质结构构建等.在这些改性策略中,异质结构建被认为是提高光催化性能最有效的方法之一,特别是S型异质结因其较好的氧化还原能力和电子转移特性而备受关注.S型异质结通常由一个氧化型光催化剂和一个还原型光催化剂组成,在两者的接触界面上形成内建电场,促使无用的载流子复合,从而保留更多具有强氧化还原能力的空穴和电子,以此提高异质结光催化性能.ZnIn₂S₄具有合适的带隙和高导带位置,可以作为还原型光催化剂与ZnO构建S型异质结,...     

Achieving indirect-to-direct band gap transition and enhanced photocatalytic performance in blue phosphorene through doping and strain

Recently, blue phosphorene (BP) has demonstrated great potential in the field of photocatalytic water splitting due to the ultrahigh carrier mobility. However, the practical application of BP as an efficient photocatalyst is greatly limited by its indirect band gap. In this work, we investigate the synergistic effect of substitutional doping and biaxial strain on the electronic and photocatalytic properties of BP using hybrid density functional calculations. The results show that As/Sb doping not only reduces the band gap of BP without introducing any midgap states but also turns it into direct band gap semiconductor, which can be ascribed to the p states of the dopants appearing around the band edges. For these As/Sb-doped BP systems, the band gaps, band edge positions, and optical absorption abilities can be further tuned by applying a biaxial strain. In particular, we predict that compressive strains are more propitious for the doped systems than the tensile strains since the requirements for water splitting are satisfied, meanwhile preserving the direct band gap characteristics. Besides, our calculations also show that the band gap and the reducing and oxidizing power of multilayer BP are highly dependent on the layer thickness. These results suggest feasible modulation strategies for enabling BP to be a visible-light-driven photocatalyst for water splitting.     

Correlation between the band positions of (SrTiO3)1-x.(LaTiO2N)x solid solutions and photocatalytic properties under visible light irradiation

N-doped SrTiO3 and (SrTiO3)1-x.(LaTiO2N)x samples were prepared by the thermal ammonolysis method. The photocatalytic activities of the samples were investigated in a water suspension system. Aqueous methanol solution (50 mL CH3OH + 220 mL H2O) for H2 evolution and aqueous silver nitrate solution (270 mL, 0.01 mol L(-1)) for O2 evolution were used as sacrificial reagents. The oxynitrides showed photocatalytic activities under visible light irradiation. The maximum rates of photocatalytic hydrogen and oxygen evolution under visible light irradiation (lambda > 420 nm) were 10 and 8 micromol h(-1), respectively. The samples were characterized by X-ray diffractometry, UV-Vis spectrophotometry, Fourier transform infrared spectrometry, and laser Raman spectroscopy. The unit cell edge length of (SrTiO3)1-x.(LaTiO2N)x increased linearly and their band gaps reduced from 3.18 to 2.04 eV with increasing x from 0 to 0.30. Moreover, the calculation results of (SrTiO3)0.75.(LaTiO2N)0.25 by density functional theory suggested that the band gap narrowing of the solid solutions came from the hybridization of N2p and O2p orbital. The band positions of the solid solutions were further investigated by Mott-Schottky and the onset potential method. The results suggested that the conduction band of the solid solution was lowered, which led to decrement of the hydrogen evolution rate.     

负载型纳米CdS制备及催化分解水制氢的研究进展

硫化镉(CdS)是一种研究广泛的光催化剂,禁带能为2.4 eV,可以吸收波长小于520 nm的紫外和可见光,吸收波长范围宽,作为光催化剂具有较大的优势.纯CdS的光催化效率较低,在水溶液中易发生光腐蚀,致使催化寿命缩短,限制了CdS的应用.利用载体比表面积大,易于离子交换且有利于电子传递等优点,将纳米CdS制备成负载型催化剂,可以有效地提高CdS的光催化效率与稳定性,成为CdS改性的一种有效手段.本文综述了以SiO₂、Al₂O₃、MgO、分子筛、高分子材料、层状化合物及钙钛矿型复合氧化物等为载体,制备负载型纳米CdS光催化剂的方法及其在光催化分解水制氢中的应用.     

正六棱型MoO3-x微米柱光催化剂的制备及性能

首先采用低温水相合成法制备了正六棱型MoO₃微米柱,然后以抗坏血酸为还原剂一步还原法制备了一种表面氧空位可控的MoO_3-x光催化材料。MoO_3-x具有较窄的禁带宽度和较大的光吸收范围。以罗丹明B为模拟污染物的光催化降解实验表明,随着氧空位的增加,MoO_3-x的催化活性明显增加。对于Mo⁵⁺摩尔分数为20.1%的MoO2.799样品,降解90%的初始质量浓度为10 mg/L的罗丹明溶液只需要60 min。本研究为高性能半导体光催化材料的制备提供了一种新思路。     

Electrochemical Determination of the Energy Level of Organic Electroluminescent Materials

The studies of energy level of organic/polymeric (organic) systems play a key role in organic light emitting devices (LED). Investigating of energy level not only involves determination of the band gap (E_g) of organic materials, but also involves determination of the absolute energy positions of the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO). The most widely used method for determination of the band gap values of organic materials is optical absorption spectroscopy,however, this method can not provide the absolute band edge positions of E_LUM0 and E_HOMO. Quantum chemical calculations (such as VEH) can also provide the values of E_g and E_H0M0, but it is usually complicated and time-consuming. The photoemission analysis has also been investigated recently for determining the HOMO position of organic systems, however, the high price of the determination systems by this method leads to the limitation to use of it.     

LaOCl-Coupled Polymeric Carbon Nitride for Overall Water Splitting through a One-Photon Excitation Pathway

It is a challenge to explore photocatalytic materials for sunlight-driven water splitting owing to the limited choice of a single semiconductor with suitable band energy levels but with a minimized band gap for light harvesting. Here, we report a one-photon excitation pathway by coupling polymeric carbon nitride (PCN) semiconductor with LaOCl to achieve overall water splitting. This artificial photosynthesis composite catalyzes the decomposition of H₂O into H₂ and O₂, with evolution rates of 22.3 and 10.7 μmol h⁻¹, respectively. The high photocatalytic performance of PCN/LaOCl can be ascribed to the simultaneously accomplished reduction and oxidation of water on LaOCl and PCN domains, respectively, as well as the fast charge separation and migration induced by the interfacial electric field related to LaOCl modification. This study provides new insights on the development of composite photocatalysts for pure water splitting based on polymer-based materials via charge modulation.     

Carbon-based H2-production photocatalytic materials

Photocatalytic hydrogen production from water splitting is of promising potential to resolve the energy shortage and environmental concerns. During the past decade, carbon materials have shown great ability to enhance the photocatalytic hydrogen-production performance of semiconductor photocatalysts. This review provides a comprehensive overview of carbon materials such as CNTs, graphene, C₆₀, carbon quantum dots, carbon fibers, activated carbon, carbon black, etc. in enhancing the performance of semiconductor photocatalysts for H₂ production from photocatalytic water splitting. The roles of carbon materials including supporting material, increasing adsorption and active sites, electron acceptor and transport channel, cocatalyst, photosensitization, photocatalyst, band gap narrowing effect are explicated in detail. Also, strategies for improving the photocatalytic hydrogen-production efficiency of carbon-based photocatalytic materials are discussed in terms of surface chemical functionalization of the carbon materials, doping effect of the carbon materials and interface engineering between semiconductors and carbon materials. Finally, the concluding remarks and the current challenges are highlighted with some perspectives for the future development of carbon-based photocatalytic materials.     

Indium induced band gap tailoring in AgGa(1-x)In(x)S(2) chalcopyrite structure for visible light photocatalysis

Indium was substituted at gallium site in chalcopyrite AgGaS(2) structure by using a simple solid solution method. The spectroscopic analysis using extended x-ray absorption fine structure and x-ray photoelectron spectroscopy confirmed the indium substitution in AgGaS(2) lattice. The band gap energy of AgGa(1-x)In(x)S(2) (x=0-1) estimated from the onset of absorption edge was found to be reduced from 2.67 eV (x=0) to 1.9 eV (x=1) by indium substitution. The theoretical and experimental studies showed that the indium s orbitals in AgGa(1-x)In(x)S(2) tailored the band gap energy, thereby modified the photocatalytic activity of the AgGa(1-x)In(x)S(2).     

Engineering the Band Gap States of the Rutile TiO2(110) Surface by Modulating the Active Heteroatom

Introducing band gap states to TiO₂ photocatalysts is an efficient strategy for expanding the range of accessible energy available in the solar spectrum. However, few approaches are able to introduce band gap states and improve photocatalytic performance simultaneously. Introducing band gap states by creating surface disorder can incapacitate reactivity where unambiguous adsorption sites are a prerequisite. An alternative method for introduction of band gap states is demonstrated in which selected heteroatoms are implanted at preferred surface sites. Theoretical prediction and experimental verification reveal that the implanted heteroatoms not only introduce band gap states without creating surface disorder, but also function as active sites for the Cr^VI reduction reaction. This promising approach may be applicable to the surfaces of other solar harvesting materials where engineered band gap states could be used to tune photophysical and ‐catalytic properties.     

Double-hole-mediated coupling of anionic dopants in perovskite NaNbO3 for efficient solar water splitting

Doping is an effective strategy to improve the photocatalytic performances of semiconductor photocatalyst for water splitting. In this work, we perform extensive hybrid density functional calculations to investigate perovskite NaNbO₃ with anionic monodoping with N, C, P, and S dopants as well as with (N + N), (C + S), and (N + P) codoping pairs. Theoretical results clearly reveal that the band structures of NaNbO₃ can be effectively tailored by introducing double-hole-mediated coupling of anion-anion pairs. Compared with the monodoping cases, the anion-anion codoped NaNbO₃ systems not only have substantially narrowed band gaps, but also can eliminate the unoccupied localized states appearing above the Fermi level, which are disastrous for photocatalysis as they may trap the photogenerated carriers. Optical absorption curves further convince that the codoped NaNbO₃ can effectively harvest visible light. The band edge positions with respect to the redox potentials of water demonstrate that the (N + N) codoped NaNbO₃ are desirable for efficient solar water splitting.