具有金属薄层的p-Si阴极在碱溶液中的光电化学性能

本文用循环伏安曲线和恒电位极化方法考察了具有金属薄层的p型单晶外延硅(p⁺/p-Si)阴极在碱溶液中的光电化学性能。结果表明,镀有钨-镍合金层的p⁺/p-Si阴极和镀有钯的p⁺/p-Si阴极,使氢析出的光电流明显增加。前者的电位比光电流达到相同值的空白p⁺/p-Si电极向正方移动了0.3V以上,后者移动0.25V。同时对p型外延硅(p⁺/p-Si)阴极比p型单晶硅(p-Si)阴极光响应较大的实验结果作了初步解释。扫描电镜结果显示,钨-镍合金沉积层是由许多不连续的“团块”构成的,而不是连续层。     

湿化学法制备硅纳米线阵列及其光电化学产氢性能分析

为了探究不同方法条件下制备的硅纳米线阵列电极产氢性能异同,文中分别采用了两步金属辅助催化无电刻蚀法、一步金属辅助催化无电刻蚀法以及阳极氧化法来制备硅纳米线阵列用作为光电分解水电池光阴极材料.通过FESEM、XRD和UV-Vis-IRDRS等手段对实验样品的形貌、晶型、减反性表征,发现相比于其他2种方法所得硅纳米线样品,两步金属辅助催化无电刻蚀法制备的硅纳米线结构晶型保持更好,表面缺陷更少.光电化学测试表明两步金属辅助催化无电刻蚀法制备的硅纳米线光电化学性能表现最优,其光电流密度值是一步法的4倍,阳极氧化法的40倍;转移电荷电阻仅是一步法制备的硅纳米线阵列阻值的1/3,阳极氧化法制备的1/1000.     

n-型多孔Si/TiO2纳米线异质结构的制备及光电化学性能

采用光辅助电化学腐蚀法制备了n-型多孔硅衬底, 再采用水热法在其表面生长TiO₂纳米线制得了三维n-型多孔Si/TiO₂纳米线异质结构. 通过X射线衍射、 扫描电子显微镜和X射线能量散射等表征证实了n-型多孔Si/TiO₂纳米线异质结构的形成. 紫外-可见漫反射光谱测试结果表明, n-型多孔硅与TiO₂纳米线的复合提高了紫外-可见波段的光吸收. 光电性能测试结果表明, 3个样品中n-型多孔Si/TiO₂纳米线异质结作为光电极的光电流最高, 这说明n-型多孔Si/TiO₂纳米线作为光电极具有更高的光电化学分解水性能.     

湿化学法制备硅纳米线阵列及其光电化学产氢性能分析

为了探究不同方法条件下制备的硅纳米线阵列电极产氢性能异同,文中分别采用了两步金属辅助催化无电刻蚀法、一步金属辅助催化无电刻蚀法以及阳极氧化法来制备硅纳米线阵列用作为光电分解水电池光阴极材料。通过FESEM、XRD和UVVis-IR DRS等手段对实验样品的形貌、晶型、减反性表征,发现相比于其他2种方法所得硅纳米线样品,两步金属辅助催化无电刻蚀法制备的硅纳米线结构晶型保持更好,表面缺陷更少。光电化学测试表明两步金属辅助催化无电刻蚀法制备的硅纳米线光电化学性能表现最优,其光电流密度值是一步法的4倍,阳极氧化法的40倍;转移电荷电阻仅是一步法制备的硅纳米线阵列阻值的1/3,阳极氧化法制备的1/1 000。     

聚吡咯纳米阵列电极的光电化学

以多孔的铝阳极氧化膜(AAO)为模板制备了直径约为80 nm聚吡咯(PPy)纳米线的阵列电极, 并研究了它的光电化学响应. 结果表明, 在电极电位低于－0.1 V(vs Ag/AgCl)时出现的阴极光电流是由聚吡咯纳米线的p型半导体性质引起的, 其平带电位为－0.217 V. 聚吡咯纳米线的长度对光电流的影响较大, 最佳长度为42 nm. 这是因为在很短的聚吡咯纳米线阵列中PPy太少, 产生的光电流弱, 而在过长的聚吡咯纳米线阵列中光生电子在到达电极基底前易于与光生空穴复合而消失. 聚吡咯纳米线有可能作为纳米光电器件用于未来微器件系统.     

非晶TiO2修饰CuBi2O4光阴极增强其光电化学产氢活性

光催化作为太阳能利用领域的研究热点引起了广泛的关注.其中,光电化学技术能够通过分解水提供清洁的氢能源,因此被认为是一种潜在的新能源制造方式.在光电化学分解水产氢的过程中,最重要的是高效光电极的制备.一系列n型半导体材料已被广泛地报道并用作光阳极,如BiVO4,ZnO,Fe2O3等.然而对于光阴极材料,其可选择性则较少.CuBi2O4是一种天然矿物,具有廉价易得以及化学性质稳定的特性,而且是一种p型半导体材料,因此能够用于制备光阴极;另外因为其强的可见光响应(1.70 eV),所以具有广泛的应用前景.目前对于CuBi2O4光阴极研究主要集中在合成和理论计算方面,而对于如何促进界面处的载流子分离研究较少.本文通过一种简单的电沉积方法成功制备出CuBi2O4光阴极,然后利用非晶TiO2和助催化剂Pt进行修饰后将其用于光电化学产氢.由于形成了CuBi2O4/TiO2 p-n结,因此其光阴极活性得到增强.新的Pt/TiO2/CuBi2O4光阴极在0.60 V偏压处的光电流为0.35 mA/cm2,其数值约为Pt/CuBi2O4光阴极的两倍.XRD结果表明,我们制备的CuBi2O4为纯相且结晶性较好,其表面修饰的TiO2为非晶相的.SEM结果表明,CuBi2O4电极层由100-150 nm的颗粒构成.紫外-可见吸收光谱表明,制备的CuBi2O4光电极拥有良好的可见光吸收性质,而且TiO2修饰未对CuBi2O4的光吸收产生明显的影响.XPS结果表明,修饰TiO2并未对CuBi2O4电极造成成分上的破坏.光电化学测试表明,修饰TiO2层厚度和结晶性会影响光电极的最终活性.修饰四层TiO2和退火200 oC的样品具有最好的活性.另外稳定性测试也表明,修饰非晶TiO2的CuBi2O4光阴极具有良好的稳定性.在IPCE测试中,Pt/TiO2/CuBi2O4光阴极在其光响应范围内均比Pt/CuBi2O4光阴极表现出更高的效率.阻抗结果测试中Pt/TiO2/CuBi2O4光阴极具有更小的阻抗,这表明其载流子传输更加高效.在Mott-Shetty测试中,Pt/TiO2/CuBi2O4和Pt/CuBi2O4光阴极都表现出p型半导体性质,但是Pt/TiO2/CuBi2O4具有更负的平带电位,这表明修饰的TiO2仍具有n型半导体材料的特性,并与p型的CuBi2O4形成p-n结,从而促进了载流子分离效率.     

非晶TiO_2修饰CuBi_2O_4光阴极增强其光电化学产氢活性（英文）

光催化作为太阳能利用领域的研究热点引起了广泛的关注.其中,光电化学技术能够通过分解水提供清洁的氢能源,因此被认为是一种潜在的新能源制造方式.在光电化学分解水产氢的过程中,最重要的是高效光电极的制备.一系列n型半导体材料已被广泛地报道并用作光阳极,如BiVO_4,ZnO,Fe_2O_3等.然而对于光阴极材料,其可选择性则较少.CuBi_2O_4是一种天然矿物,具有廉价易得以及化学性质稳定的特性,而且是一种p型半导体材料,因此能够用于制备光阴极;另外因为其强的可见光响应(1.70 eV),所以具有广泛的应用前景.目前对于CuBi_2O_4光阴极研究主要集中在合成和理论计算方面,而对于如何促进界面处的载流子分离研究较少.本文通过一种简单的电沉积方法成功制备出CuBi_2O_4光阴极,然后利用非晶TiO_2和助催化剂Pt进行修饰后将其用于光电化学产氢.由于形成了CuBi_2O_4/TiO_2 p-n结,因此其光阴极活性得到增强.新的Pt/TiO2/CuBi_2O_4光阴极在0.60V偏压处的光电流为0.35 mA/cm~2,其数值约为Pt/CuBi_2O_4光阴极的两倍.XRD结果表明,我们制备的CuBi_2O_4为纯相且结晶性较好,其表面修饰的TiO_2为非晶相的.SEM结果表明,CuBi_2O_4电极层由100-150nm的颗粒构成.紫外-可见吸收光谱表明,制备的CuBi_2O_4光电极拥有良好的可见光吸收性质,而且TiO_2修饰未对CuBi_2O_4的光吸收产生明显的影响.XPS结果表明,修饰TiO_2并未对CuBi_2O_4电极造成成分上的破坏.光电化学测试表明,修饰TiO_2层厚度和结晶性会影响光电极的最终活性.修饰四层TiO_2和退火200℃的样品具有最好的活性.另外稳定性测试也表明,修饰非晶TiO_2的CuBi_2O_4光阴极具有良好的稳定性.在IPCE测试中,Pt/TiO_2/CuBi_2O_4光阴极在其光响应范围内均比Pt/CuBi_2O_4光阴极表现出更高的效率.阻抗结果测试中Pt/TiO_2/CuBi_2O_4光阴极具有更小的阻抗,这表明其载流子传输更加高效.在Mott-Shetty测试中,Pt/TiO_2/CuBi_2O_4和Pt/CuBi_2O_4光阴极都表现出p型半导体性质,但是Pt/TiO_2/CuBi_2O_4具有更负的平带电位,这表明修饰的TiO_2仍具有n型半导体材料的特性,并与p型的CuBi_2O_4形成p-n结,从而促进了载流子分离效率.     

H?O

光电化学分解水可将太阳能转换为绿色的氢能,为目前的能源危机和环境问题提供了一种理想的解决方案.在分解水反应中,涉及四空穴过程的产氧半反应是制约性能的关键步骤,往往需要在半导体表面沉积电催化剂以加速产氧反应动力学.因此,全面理解电催化剂在光电化学分解水体系中的作用至关重要.在目前的产氧电催化剂中,过渡金属羟基氧化物电催化剂(MOOH, M=Fe, Co, Ni)因其环保、廉价、高效以及稳定的特性,已被广泛用于半导体光阳极分解水器件中.而且, MOOH可用简单的电沉积方法沉积在光电极表面,易于大面积制备.然而,电沉积法制备的MOOH具有复杂的结构,对其作用机制的全面理解更加困难.因此,本文以电沉积MOOH修饰的硅基光阳极(n+p-Si/SiOx/Fe/FeOx/MOOH)作为模型,研究了不同电催化剂对硅光阳极光电化学产氧性能的影响.实验发现电催化剂的界面优化在电催化剂修饰的光电极中发挥着重要作用,这是因为优化的界面可以提升界面电荷传输,提供更多的催化反应活性位点以及更高的本征催化活性,从而更有利于光解水性能的提升.该项研究揭示了电催化剂在光解水器件中的作用,并为今后高效光解水器件的设计提供了一定指导.首先在多晶n+p-Si基底上热蒸镀了一层30 nm的金属Fe膜,并通过电化学活化将Fe膜表面转换为FeOx得到Fe/FeOx (记作a Fe)界面层,然后利用电沉积方法制备MOOH表面修饰层,最终得到n+p-Si/SiOx/a Fe:MOOH光阳极.X射线光电子能谱、拉曼光谱以及扫描电子显微镜表面元素成像的表征结果均证实电极表面由于界面层金属Fe元素的掺杂而形成了Fe1-xNixOOH.在模拟太阳光下用于光解水产氧时, n+p-Si/SiOx/aFe:NiOOH电极的起始电位为～1.01 VRHE (相对于可逆氢电极的电势),在1.23 VRHE下的光电流为38.82 mAcm–2,显著优于n+p-Si/SiOx/aFe、 n+p-Si/SiOx/aFe:FeOOH以及n+p-Si/SiOx/aFe:CoOOH三个对比样品,且其稳定性达到75 h.另外,我们发现n+p-Si/SiOx/aFe:MOOH电极的光电化学产氧性能均显著高于n+p-Si/SiOx/aFe电极,且p++-Si/SiOx/aFe:MOOH的电催化产氧性能也高于p++-Si/SiOx/MOOH,不仅证明了aFe界面层对Si与MOOH层之间的界面接触作用的有效调控,而且表明双电催化剂体系(aFe:MOOH)的电催化产氧活性高于单电催化剂(MOOH).热力学分析表明, n+p-Si/SiOx/a Fe:MOOH光阳极的光电压大小与其光解水产氧性能并不一致,从而排除了热力学因素对性能的关键影响.进一步从塔菲尔斜率、电化学活性表面积和电化学阻抗谱对各电极的动力学进行了分析,证明了动力学因素在上述光阳极产氧性能中的主导作用.同时发现,由于a Fe:NiOOH双电催化剂具有更高的本征电催化产氧性能,提供了更多的表面活性位点以及更有效地促进了光生载流子的传输,对动力学的提升效果更显著,从而使n+p-Si/SiOx/aFe:NiOOH光阳极表现出最高的光解水产氧性能.     

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.     

CuInSe2/氰桥混配物复合修饰光电极的制备及其光电性质

利用电沉积法在氰桥混配物预修饰的玻璃碳电极上再沉积CuInSe2半导体材料,制备了一种复合型修饰光电极(Eu-Fe-Mo/CuInSe2)。以含Cu2+、In3+、SeO23-及柠檬酸钠的酸性水溶液为电镀液,通过优化寻找到电镀液中最佳的Cu∶In∶Se料液比例,用恒电位电沉积法可以制备出具有良好光电效应的复合型修饰光电极。用SEM、EDS技术对复合修饰光电极的表面形貌及其修饰材料的元素组成进行了表征;以60 W的普通日光型白炽灯为光源,采用开路电压和计时安培法研究了该复合修饰光电极的光电性质。测得该光电极的响应光电压大于30 mV,响应光电流密度大于8.9×10-6A/cm2。实验结果表明,该复合修饰光电极呈现典型p型半导体的光电性质。     

III-V nitride epilayers for photoelectrochemical water splitting: GaPN and GaAsPN

Epilayers of single-crystal GaAsPN and GaPN semiconductor samples with varying nitrogen compositions were photoelectrochemically characterized to determine their potential to serve as water splitting photoelectrodes. The band gap and flatband potentials were determined and used to calculate the valence and conduction band edge energies. The band edges for all compositions appear to be too negative by more than 500 mV for any of the materials to effect light-driven water splitting without an external bias. Corrosion analysis was used to establish material stability under operating conditions. GaPN was found to show good stability toward photocorrosion; on the other hand, GaAsPN showed enhanced photocorrosion as compared to GaP.     

Self-powered anti-interference photoelectrochemical immunosensor based on Au/ZIS/CIS heterojunction photocathode with zwitterionic peptide anchoring

Accurate detection of important biomarkers with ultra-low levels in complex biological matrix is one of the frontier scientific issues because of possible signal interference of potential reductive agents and protein molecules. Herein, a self-powered anti-interference photoelectrochemical (PEC) immunosensor was explored for sensitive and specific detection of model target of cardiac troponin I (cTnI). Specifically, a novel ternary heterojunction served as the photocathode to offer a remarkable current output and a zwitterionic peptide was introduced to build a robust antifouling biointerface. CuInS₂ (CIS) film with porous network nanostructure was first prepared and then modified in order with ZnIn₂S₄ (ZIS) nanocrystals and Au nanoparticles to fabricate the Au/ZIS/CIS heterojunction photocathode. After capture cTnI antibody (Ab) was immobilized, the zwitterionic peptide KAEAKAEAPPPPC was then anchored to compete the immunosensor. The elaborated PEC immunosensor exhibited high sensitivity for target cTnI antigen (Ag) detection, with good anti-interference against reductive agents and nonspecific proteins. This integration strategy of heterojunction photocathode with zwitterionic peptide provides a new sight to develop advanced PEC immunosensors applying in practical biosamples.     

CuO/Cu2O nanowire array photoelectrochemical biosensor for ultrasensitive detection of tyrosinase

Photoelectrochemical(PEC) biosensors have shown great promise in bioanalysis and diagnostic applications in recent years. In this work, the CuO/Cu_2O nanowire array(CuO/Cu_2O Nanowire) supported on copper foam was prepared as a photocathode for detection of tyrosinase though quinone-chitosan conjugation chemistry method. The in-situ generated quinones that were the catalytic product of tyrosinase acted as electron acceptors, which were captured by the chitosan deposited on the surface of the electrode. Direct immobilization of electron acceptor on the electrode surface improved the photocurrent conversion efficiency and thus sensitivity. The as-prepared biosensor can realize a rapid response in a wide linear range of 0.05 U/mL to 10 U/mL with the detection limit as low as 0.016 U/mL of tyrosinase. The current work provides a new perspective to design and develop highly sensitive and selective PEC biosensor.     

Highly efficient photoelectrochemical hydrogen generation using a ZnO nanowire array and a CdSe/CdS co-sensitizer

Highly efficient photoelectrochemical (PEC) hydrogen generation was achieved by fabricating CdSe deposited ZnO/CdS core/shell nanowire (NW) array photoanodes by a facile three-step solution-based method. Well-defined electrical pathways in 1-dimensional (1D) NW structures allowed efficient charge carrier collection, and CdSe/CdS co-sensitization enabled utilization of the visible region in the solar spectrum. PEC devices using CdSe/CdS/ZnO NW arrays showed improved absorption spectra, and they demonstrated a remarkable enhancement in PEC performance. Our proposed structure is a promising candidate photoanode for solar energy-to-hydrogen conversion devices.     

Unassisted solar water splitting using a Cu2O/Ni(OH)2-ZnO/Au tandem photoelectrochemical cell

Journal of Solid State Electrochemistry - A tandem photoelectrochemical (PEC) cell consisting of a Cu2O/Ni(OH)2 photocathode and a ZnO/Au photoanode was investigated for unassisted solar water...     

外延p-Si中的高-低结对光电化学转换效率的影响

本文采用p⁺/p-Si作为光阴极进行了光电化学电池和光助析氢电池的研究,光转换效率分别达到了7.4%(V^2+/3+电对)和7.8%(Co—W修饰),并讨论了导致高效率的原因,强调了高-低结对于改善半导体光电极性能的重要性。     

Surfactant-free, large-scale, solution-liquid-solid growth of gallium phosphide nanowires and their use for visible-light-driven hydrogen production from water reduction

Colloidal GaP nanowires (NWs) were synthesized on a large scale by a surfactant-free, self-seeded solution-liquid-solid (SLS) method using triethylgallium and tris(trimethylsilyl)phosphine as precursors and a noncoordinating squalane solvent. Ga nanoscale droplets were generated in situ by thermal decomposition of the Ga precursor and subsequently promoted the NW growth. The GaP NWs were not intentionally doped and showed a positive open-circuit photovoltage based on photoelectrochemical measurements. Purified GaP NWs were used for visible-light-driven water splitting. Upon photodeposition of Pt nanoparticles on the wire surfaces, significantly enhanced hydrogen production was observed. The results indicate that colloidal surfactant-free GaP NWs combined with potent surface electrocatalysts could serve as promising photocathodes for artificial photosynthesis.     

High-performance bulk heterojunction-based photocathode with facile architecture for photoelectrochemical water splitting

Organic semiconductors are promising candidates as photoactive layers for photoelectrodes used in photoelectrochemical (PEC) cells due to their excellent light absorption and efficient charge transport properties with the help of interfacial materials. However, the use of multilayers will make the charge transfer mechanism more complicated and decrease the PEC performance of the photoelectrode caused by the increased contact resistance. In this work, a PM6:Y6 bulk heterojunction (BHJ)-based photocathode is fabricated for efficient PEC hydrogen evolution reaction (HER) in an acidic aqueous solution. With RuO₂ as an interfacial modification layer, the photocathode with a simple structure (fluorine-doped tin oxide (FTO)/PM6:Y6/RuO₂) generates a maximum photocurrent density up to ?15 mA/cm² at 0 V vs. reference hydrogen electrode (RHE), outperforming all previously reported BHJ-based photocathodes in terms of PEC performance. The highest ratiometric power-saved efficiency of 3.7% is achieved at 0.4 V vs. RHE.     

Identifying Copper Vacancies and Their Role in the CuO Based Photocathode for Water Splitting

Metal oxides are an important family of semiconductors for effective photoelectrodes in solar‐to‐chemical energy conversion. Defect engineering, such as modification of oxygen vacancy density, has been extensively applied in tailoring the optoelectric properties of photoelectrodes. Very limited attention has been paid to the influence of metal vacancies. Herein, we study metal vacancies in a typical CuO photocathode for photoelectrochemical (PEC) water splitting. The Cu vacancies can improve the charge carrier concentration, and facilitate the charge separation and transfer in the CuO photocathode. By changing the O₂ partial pressure, the density of Cu vacancies can be tuned, which leads to improved PEC performance. The CuO photocathode prepared in pure O₂ exhibits a 100 % photocurrent increase compared to that prepared in air. The promotion effect of Cu vacancies on the PEC is also observed in other Cu based photocathodes, showing the generic role of metal vacancies in efficient photocathodes.     

Highly luminescent InP/GaP/ZnS nanocrystals and their application to white light-emitting diodes

Highly stable and luminescent InP/GaP/ZnS QDs with a maximum quantum yield of 85% were synthesized by in situ method. The GaP shell rendered passivation of the surface and removed the traps. TCSPC data showed an evidence for the GaP shell. InP/GaP/ZnS QDs show better stability than InP/ZnS. We studied the optical properties of white QD-LEDs corresponding to various QD concentrations. Among various concentrations, the white QD-LEDs with 0.5 mL of QDs exhibited a luminous efficiency of 54.71 lm/W, Ra of 80.56, and CCT of 7864 K.