BiOBr/g-C3N4 S型异质结无H2O2光-自芬顿高效催化降解RhB

通过焙烧-超声混合法成功地制备了BiOBr/g-C₃N₄ S型异质结复合光催化剂。采用多种表征手段对样品物理属性进行了表征,包括X射线多晶粉末衍射仪(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、紫外可见漫反射光谱(UV-VisDRS)。研究了所制备样品有/无Fe³⁺的光-自芬顿催化/光催化降解罗丹明B (RhB)性能。通过捕获实验确定了光催化反应中的主要活性物种,提出了光-自芬顿反应的降解机理。研究结果表明,BiOBr/g-C₃N₄ S型异质结能原位生成H₂O₂,添加Fe³⁺后,H₂O₂被原位活化成活性物种且光生电流和载流子分离效率获得显著提高。该光-自芬顿过程能高效降解RhB,其反应速率常数为0.208 min^-1,约为无Fe³⁺光催化反应速率常数的5.3倍,在光-自芬顿循环使用过程中表现出良好的稳定性。Fe³⁺的加入促进了光生电荷的分离和H₂O₂的活化,超氧阴离子自由基(·O₂^-)、空穴和羟基是光-自芬顿催化过程中的主要活性物种,且·O₂^-作用更大。     

钙钛矿氧化物H_(1.9)K_(0.3)La_(0.5)Bi_(0.1)Ta_2O_7和Pt/WO_3组成的Z体系下完全光解水性能

以质子化层状钙钛矿氧化物H1.9K0.3La0.5Bi0.1Ta2O7(HKLBT)作为产氢催化剂,Pt/WO3作为产氧催化材料进行Z型体系下完全分解水反应.考察了不同载流子传递介质及不同载流子浓度对反应活性的影响.结果表明,以Fe2+/Fe3+为载流子传递介质时可以实现水的完全分解(H2/O2体积比为2:1),8 mmol·L-1的FeCl3作为初始载流子传递介质时,产氢、产氧活性分别为66.8和31.8μmol·h-1,氢氧体积比为2.1:1.受光催化材料对载流子传递介质氧化还原速度的限制,过高的载流子传递介质浓度并不能提高光催化活性.     

表面缺陷α-Fe2O3(001)纳米片双活性位点类芬顿催化剂用于降解污染物

纯Fe₂O₃表面活性位点较少具有较低的催化活性限制了其在多相芬顿催化体系中的应用。通常采用元素掺杂、贵金属负载以及与其它化合物质复合等改性措施来提升催化活性,然而这些措施存在催化剂制备复杂,制备成本高以及催化剂的精细结构难以精准控制等问题。因此,本文提出在α-Fe₂O₃表面引入氧空位缺陷构筑双活性位点（Fe²⁺和氧空位）用于促进H₂O₂分解提高降解污染物降解效率。实验结果发现α-Fe₂O_3-x-330/H₂O₂体系具有较宽的pH使用范围（pH=2~10）。当pH=4时,罗丹明B的降解速率常数为0.834 h^-1,而且催化剂具有磁性,易回收重复使用。催化机理研究表明氧空位缺陷α-Fe₂O_3-x催化剂的氧空位和Fe²⁺两种活性位点均可促进H₂O₂分解,而且氧空位的引入有利于污染物在催化剂表面的吸附进一步提高催化性能。     

Cr掺杂对K2La2Ti3O10光催化活性的影响

通过溶胶-凝胶法制备了层状钙钛矿结构的K₂La₂Ti₃O₁₀及Cr掺杂的K₂La₂Ti₃O₁₀，采用X-射线衍射(XRD)、紫外可见漫反射光谱(DRS)、X射线光电子能谱(XPS)等对K₂La₂Ti₃O₁₀及Cr掺杂K₂La₂Ti₃O₁₀进行了表征。以I^-为电子给体、分别在紫外和可见光辐射下研究了K₂La₂Ti₃O₁₀及Cr掺杂K₂La₂Ti₃O₁₀光催化分解水的产氢活性。采用第一性原理，计算了Cr掺杂对K₂La₂Ti₃O₁₀半导体能带结构和态密度的影响，从电子结构的变化揭示了掺杂引起光催化活性差异的原因。结果表明，Cr的掺入能够改善和提高K₂La₂Ti₃O₁₀的光解水的产氢活性；Cr改善和提高K₂La₂Ti₃O₁₀的光解水的产氢活性存在一个最佳的掺杂浓度；当Cr与Ti的物质量的比为0.02∶1时，紫外光催化分解水产氢速率为1 500 μmol·L^-1·h^-1，可见光催化分解水产氢速率为83.6 μmol·L^-1·h^-1，分别为K₂La₂Ti₃O₁₀掺杂改性前产氢速率的26和5倍。     

时间分辨红外光谱研究Cr价态在La,Cr共掺杂SrTiO3光催化剂中的作用

使用时间分辨红外光谱研究了经H₂和O₂处理的La和Cr共掺杂SrTiO₃的光生电子动力学. X射线光电子能谱和Raman光谱结果表明, H₂处理后样品中的Cr均是+3价, 而O₂处理后Cr为+3和+6价. 使用355和532 nmm激光激发样品所得时间分辨红外光谱表明, 相比在Cr⁶⁺存在时, 光生电子衰减速率在Cr³⁺存在的情况下要慢, 这说明Cr³⁺更有利于抑制光生电子空穴的复合, 从而增加光催化产氢的活性.     

La1－xSrxNi1－yFeyO3型钙钛矿双功能氧电极的电化学性能研究

采用溶胶-凝胶法制备了一系列La_1－xSr_xNi_1－yFe_yO₃ (x＝0, 0.1, 0.2, 0.5; y＝0～1.0)型的钙钛矿催化剂, 以活性碳为载体, PTFE乳液为粘接剂制备双功能氧电极. 对催化剂进行了XRD结构分析以及SEM分析和BET比表面积测量. 采用三电极体系测试了氧电极的稳态极化曲线和电化学交流阻抗谱并对其阴极极化和阳极极化的交流阻抗谱图进行分析. 通过等效电路的拟合研究了该系列双功能氧电极氧还原反应的工作机理. 实验表明对于LaNiO₃化合物, B位掺杂可显著提高催化剂的电催化性能; 电极氧还原反应的极化主要由电荷转移反应和Nernstian扩散过程造成. 通过各个电极对于催化分解H₂O₂的分解速率常数的测定得知, Ni离子对于催化H₂O₂分解反应的活性大于Fe离子, 继续在对于氧还原反应和氧析出反应都具有较高电催化活性的LaNi_0.8Fe_0.2O₃催化剂上进行A位掺杂Sr离子后显著提高了催化剂分解H₂O₂的催化活性, 主要是因为氧空位的增多和金属离子d电子含量的降低有利于催化分解H₂O₂的活性的提高, 但由于氧空位的增多导致催化剂电导率的降低, 所以其电催化活性降低了. 通过多圈循环伏安扫描的测试, 催化剂LaNi_0.8Fe_0.2O₃有很好的稳定性.     

AxMn1-xFe2O4铁氧体(A=Zn,Ni)中阳离子的占位有序化行为研究

基于尖晶石晶体结构信息,本文采用热力学三亚晶格模型,将材料热力学计算和第一性原理计算相结合,研究了Zn_xMn_1-x Fe₂O₄和Ni_xMn_1-xFe₂O₄立方相中的Zn²⁺、Ni²⁺、Mn²⁺以及Fe³⁺在8a和16d亚晶格上的占位有序化行为。结果表明:在锰铁氧体中,室温下Mn²⁺完全占据在8a亚晶格上,Fe³⁺完全占据在16d亚晶格上,属于正尖晶石结构;随着热处理温度升高,在1 273 K达到热处理平衡时的占位构型为(Fe_0.09³⁺Mn_0.91²⁺)[Fe_1.91³⁺Mn_0.09²⁺]O₄,在热处理温度升至1 473 K时,达到热处理平衡时的占位构型为(Fe_0.11³⁺ Mn_0.89²⁺)[Fe_1.89³⁺Mn_0.11²⁺]O₄,均与实验结果符合较好。在锌铁氧体中,室温下Zn²⁺完全占据在8a亚晶格上,Fe³⁺完全占据在16d亚晶格上,属于正尖晶石结构;在热处理温度较高时,Zn²⁺和Fe³⁺发生部分置换,符合实验结果。在镍铁氧体中,半数的Fe³⁺在室温下占据在8a亚晶格上,Ni²⁺与剩下另一半的Fe³⁺共同占据在16d亚晶格上,仅在热处理温度较高的时候发生微弱变化,亦与已有的实验结果吻合。在此基础上,本文进一步通过热力学预测建立了立方相尖晶石结构的Zn_xMn_1-xFe₂O₄、Ni_xMn_1-xFe₂O₄复合体系中阳离子占位行为与热处理温度对占位的影响。     

SnO2/TiO2纳米管复合光催化剂的性能及失活再生

基于微波水热法和微乳液法合成SnO₂/TiO₂纳米管复合光催化剂. 通过X射线衍射（XRD）、配有能量色散X射线光谱仪（EDX）的透射电镜（TEM）和电化学手段对光催化剂进行表征. 以甲苯为模型污染物,考察光催化剂在紫外光（UV）和真空远紫外光（VUV）下的性能及失活再生. 结果表明,SnO₂/TiO₂纳米管复合光催化剂形成三元异质结（锐钛矿相TiO₂（A-TiO₂）/金红石相TiO₂（R-TiO₂）、A-TiO₂/SnO₂和R-TiO₂/SnO₂异质结）,促使光生电子-空穴对的有效分离,提高光催化活性. SnO₂/TiO₂表现出最佳的光催化性能,UV和VUV条件下的甲苯降解率均达100%,CO₂生成速率（k₂）均为P25的3倍左右. 但由于UV光照矿化能力不足,中间产物易在催化剂表面累积. 随着UV光照时间的增加,SnO₂/TiO₂逐渐失活,20 h 后k₂由138.5 mg·m^-3·h^-1下降到76.1 mg·m^-3·h^-1. 利用VUV再生失活的SnO₂/TiO₂,过程中产生的·OH、O₂^-·、O（¹D）、O（³P）、O₃等活性物质可氧化吸附于催化剂活性位的难降解中间产物,使催化剂得以再生,12 h后k₂恢复到143.6 mg·m^-3·h^-1. UV和VUV的协同效应使UV降解耦合VUV再生成为一种可持续的光催化降解污染物模式.     

“开放型蝶形”[2Fe2S]化合物光催化产氢性能与机理探究

合成并表征了两个新的具有 “开放型蝶形” 结构的[2Fe2S]化合物A和B; 并以A和B为催化剂、 藻红B钠盐 (EBS^2-) 为光敏剂、 三乙胺 (TEA) 为电子给体和质子源, 构建了一个均相光催化产氢体系. 结果表明: 体系在pH为12, 体积比为1∶1的CH₃CN/H₂O溶液中,产氢活性最高,经4 h可见光照射,最大产氢量分别为156.1 μmol (37.9 TON vs. A) 和18.4 μmol (TON 4.6 vs. B); 催化剂中含有质子捕获位点, 有利于形成产氢活性中间体H₂-Fe₂S₂(η²-H²-Fe^IIFe^I) 物种, 从而提高催化剂的产氢活性. 在当前的体系中, 还原态的 Fe^IFe⁰ 物种通过^1* EBS^2-转移到Fe^IFe^I中心上, 然后再经历一个EECC (化合物A) 或ECEC (化合物B), 形成产氢活性中间体H₂-Fe₂S₂(η²-H₂-Fe^IIFe^I)物种, 最终产生H₂分子, 并使Fe^IFe^I 物种再生.     

La1－xSrxNi1－yFeyO3型钙钛矿双功能氧电极的电化学性能研究

采用溶胶-凝胶法制备了一系列La_1－xSr_xNi_1－yFe_yO₃ (x＝0, 0.1, 0.2, 0.5; y＝0～1.0)型的钙钛矿催化剂, 以活性碳为载体, PTFE乳液为粘接剂制备双功能氧电极. 对催化剂进行了XRD结构分析以及SEM分析和BET比表面积测量. 采用三电极体系测试了氧电极的稳态极化曲线和电化学交流阻抗谱并对其阴极极化和阳极极化的交流阻抗谱图进行分析. 通过等效电路的拟合研究了该系列双功能氧电极氧还原反应的工作机理. 实验表明对于LaNiO₃化合物, B位掺杂可显著提高催化剂的电催化性能; 电极氧还原反应的极化主要由电荷转移反应和Nernstian扩散过程造成. 通过各个电极对于催化分解H₂O₂的分解速率常数的测定得知, Ni离子对于催化H₂O₂分解反应的活性大于Fe离子, 继续在对于氧还原反应和氧析出反应都具有较高电催化活性的LaNi_0.8Fe_0.2O₃催化剂上进行A位掺杂Sr离子后显著提高了催化剂分解H₂O₂的催化活性, 主要是因为氧空位的增多和金属离子d电子含量的降低有利于催化分解H₂O₂的活性的提高, 但由于氧空位的增多导致催化剂电导率的降低, 所以其电催化活性降低了. 通过多圈循环伏安扫描的测试, 催化剂LaNi_0.8Fe_0.2O₃有很好的稳定性.     

A Hydrogen Farm Strategy for Scalable Solar Hydrogen Production with Particulate Photocatalysts

Scalable solar hydrogen production by water splitting using particulate photocatalysts is promising for renewable energy utilization. However, photocatalytic overall water splitting is challenging owing to slow water oxidation kinetics, severe reverse reaction, and H₂/O₂ gas separation. Herein, mimicking nature photosynthesis, a practically feasible approach named Hydrogen Farm Project (HFP) is presented, which is composed of solar energy capturing and hydrogen production subsystems integrated by a shuttle ion loop, Fe³⁺/Fe²⁺. Well‐defined BiVO₄ crystals with precisely tuned {110}/{010} facets are ideal photocatalysts to realize the HFP, giving up to 71 % quantum efficiency for photocatalytic water oxidation and full forward reaction with nearly no reverse reaction. An overall solar‐to‐chemical efficiency over 1.9 % and a solar‐to‐hydrogen efficiency exceeding 1.8 % could be achieved. Furthermore, a scalable HFP panel for solar energy storage was demonstrated under sunlight outdoors.     

Van der Waals Heterostructures Comprised of Ultrathin Polymer Nanosheets for Efficient Z‐Scheme Overall Water Splitting

Inspired by natural photosynthesis, Z‐scheme photocatalytic systems are very appealing for achieving efficient overall water splitting. Developing metal‐free Z‐scheme photocatalysts for overall water splitting, however, still remains challenging. The construction of polymer‐based van der Waals heterostructures as metal‐free Z‐scheme photocatalytic systems for overall water splitting is described using aza‐fused microporous polymers (CMP) and C₂N ultrathin nanosheets as O₂‐ and H₂‐evolving catalysts, respectively. Although neither polymer is able to split pure water using visible light, a 2:1 stoichiometric ratio of H₂ and O₂ was observed when aza‐CMP/C₂N heterostructures were used. A solar‐to‐hydrogen conversion efficiency of 0.23 % was determined, which could be further enhanced to 0.40 % by using graphene as the solid electron mediator to promote the interfacial charge‐transfer process. This study highlights the potential of polymer photocatalysts for overall water splitting.     

柠檬酸络合法制备质子化层状钙钛矿K0.5La0.5Bi2Ta2O9及其光解水制氢性能

采用柠檬酸络合法制备铋层钙钛矿K_0.5La_0.5Bi₂Ta₂O₉ (KLBT), 通过酸化处理得到质子化层状钙钛矿H_1.9K_0.3La_0.5Bi_0.1Ta₂O₇(HKLBT)光催化剂, 并通过热重-差热(TG-DSC)、X射线衍射(XRD)、紫外-可见漫反射(DRS)、X射线光电子能谱(XPS)等技术对其进行了表征和分析.考察了前驱体KLBT的不同焙烧温度对HKLBT制氢活性的影响. 结果表明, 柠檬酸络合法能在较低温度下合成高结晶度纯相HKLBT, 前驱体经900℃焙烧制备的HKLBT催化剂活性最高, 在纯水中的产氢速率达236.6μmol·h^-1; 长时间活性测试表明HKLBT具有完全分解水同时产氢产氧能力,且具有较好的稳定性.     

A Hydrogen-Deficient Nickel–Cobalt Double Hydroxide for Photocatalytic Overall Water Splitting

Developing highly efficient and low-cost photocatalysts for overall water splitting has long been a pursuit for converting solar power into clean hydrogen energy. Herein, we demonstrate that a nonstoichiometric nickel–cobalt double hydroxide can achieve overall water splitting by itself upon solar light irradiation, avoiding the consumption of noble-metal co-catalysts. We employed an intensive laser to ablate a NiCo alloy target immersed in alkaline solution, and produced so-called L-NiCo nanosheets with a nonstoichiometric composition and O²⁻/Co³⁺ ions exposed on the surface. The nonstoichiometric composition broadens the band gap, while O²⁻ and Co³⁺ ions boost hydrogen and oxygen evolution, respectively. As such, the photocatalyst achieves a H₂ evolution rate of 1.7 μmol h⁻¹ under AM 1.5G sunlight irradiation and an apparent quantum yield (AQE) of 1.38 % at 380 nm.     

Hydrogen production from water decomposition by redox of Fe2O3 modified with single- or double-metal additives

Iron oxide modified with single- or double-metal additives (Cr, Ni, Zr, Ag, Mo, Mo-Cr, Mo-Ni, Mo-Zr and Mo-Ag), which can store and supply pure hydrogen by reduction of iron oxide with hydrogen and subsequent oxidation of reduced iron oxide with steam (Fe₃O₄ (initial Fe₂O₃)+4H₂↔3Fe+4H₂O), were prepared by impregnation. Effects of various metal additives in the samples on hydrogen production were investigated by the above-repeated redox. All the samples with Mo additive exhibited a better redox performance than those without Mo, and the Mo-Zr additive in iron oxide was the best effective one enhancing hydrogen production from water decomposition. For Fe₂O₃-Mo-Zr, the average H₂ production temperature could be significantly decreased to 276 °C, the average H₂ formation rate could be increased to 360.9-461.1 μmol min⁻¹ Fe-g⁻¹ at operating temperature of 300 °C and the average storage capacity was up to 4.73 wt% in four cycles, an amount close to the IEA target.     

A Hydrogen‐Deficient Nickel–Cobalt Double Hydroxide for Photocatalytic Overall Water Splitting

Developing highly efficient and low‐cost photocatalysts for overall water splitting has long been a pursuit for converting solar power into clean hydrogen energy. Herein, we demonstrate that a nonstoichiometric nickel–cobalt double hydroxide can achieve overall water splitting by itself upon solar light irradiation, avoiding the consumption of noble‐metal co‐catalysts. We employed an intensive laser to ablate a NiCo alloy target immersed in alkaline solution, and produced so‐called L‐NiCo nanosheets with a nonstoichiometric composition and O^2?/Co³⁺ ions exposed on the surface. The nonstoichiometric composition broadens the band gap, while O^2? and Co³⁺ ions boost hydrogen and oxygen evolution, respectively. As such, the photocatalyst achieves a H₂ evolution rate of 1.7 μmol h^?1 under AM 1.5G sunlight irradiation and an apparent quantum yield (AQE) of 1.38 % at 380 nm.     

Elucidation of methyl tert-butyl ether degradation with Fe/H2O2 by purge-and-trap gas chromatography-mass spectrometry

Degradation of methyl tert-butyl ether (MTBE) with Fe²⁺/H₂O₂ was studied by purge-and-trap gas chromatography-mass spectrometry. MTBE was degraded 99% within 120 min under optimum conditions. MTBE was firstly degraded rapidly based on a Fe²⁺/H₂O₂ reaction and then relatively slower based on a Fe³⁺/H₂O₂ reaction. The dissolved oxygen decreased rapidly in the Fe²⁺/H₂O₂ reaction stage, but showed a slow increase in the Fe³⁺/H₂O₂ reaction stage. tert-Butyl formate, tert-butyl alcohol, methyl acetate and acetone were identified as primary degradation products by mass spectrometry. A preliminary reaction mechanism involving two different pathways for the degradation of MTBE with Fe²⁺/H₂O₂ was proposed. This study suggests that degradation of MTBE can be achieved using the Fe²⁺/H₂O₂ process.     

Phenazine-based Compound Realizing Separate Hydrogen and Oxygen Production in Electrolytic Water Splitting

Electrocatalytic water splitting powered by renewable energy is a sustainable approach for hydrogen production. However, conventional water electrolysis may suffer from gas mixing, and the different kinetics between hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) will limit the direct use of unstable renewable energies, leading to increased cost of H₂ production. Herein, a novel phenazine-based compound is synthesized to develop the solid-state redox mediator associated water splititng process, and thus decoupling the H₂ and O₂ production in acid solution without the use of membrane. Excitingly, this organic redox mediator exhibits high specific capacity (290 mAh g⁻¹ at 0.5 A g⁻¹), excellent rate performance (186 mAh g⁻¹ at 30 A g⁻¹) and long cycle life (3000 cycles) due to its π-conjugated aromatic structure and the fast kinetics of H⁺ storage/release process. Furthermore, a membrane-free decoupled water electrolysis architecture driven by solar energy is achieved, demonstrating high-purity H₂ production at different times.