Heat transfer and temperature evolution in underground mininginduced overburden fracture and ground fissures: Optimal time window of UAV infrared monitoring

Heat transfer and temperature evolution in overburden fracture and ground fissures are one of the essential topics for the identification of ground fissures via unmanned aerial vehicle(UAV) infrared imager. In this study, discrete element software UDEC was employed to investigate the overburden fracture field under different mining conditions. Multiphysics software COMSOL were employed to investigate heat transfer and temperature evolution of overburden fracture and ground fissures under the influence of mining condition, fissure depth, fissure width, and month alternation. The UAV infrared field measurements also provided a calibration for numerical simulation. The results showed that for ground fissures connected to underground goaf(Fissure Ⅰ), the temperature difference increased with larger mining height and shallow buried depth. In addition, Fissure Ⅰ located in the boundary of the goaf have a greater temperature difference and is easier to be identified than fissures located above the mining goaf. For ground fissures having no connection to underground goaf(Fissure Ⅱ), the heat transfer is affected by the internal resistance of the overlying strata fracture when the depth of Fissure Ⅱ is greater than10 m, the temperature of Fissure Ⅱ gradually equals to the ground temperature as the fissures’ depth increases, and the fissures are difficult to be identified. The identification effect is most obvious for fissures larger than 16 cm under the same depth. In spring and summer, UAV infrared identification of mining fissures should be carried out during nighttime. This study provides the basis for the optimal time and season for the UAV infrared identification of different types of mining ground fissures.

Ti-Fe_(2)O_(3)/Ni(OH)_(x) as an efficient and durable photoanode for the photoelectrochemical catalysis of PET plastic to formic acid

Photoelectrochemical(PEC) technology provides a promising prospect for the transformation of polyethylene terephthalate(PET) plastic wastes to produce value-added chemicals.The PEC catalytic systems with high activity,selectivity and long-term durability are required for the future up-scaling industrial applications.Herein,we employed the interfacial modification strategy to develop an efficient and stable photoanode and evaluated its PEC activity for ethylene glycol(EG,derived from PET hydrolysate) oxidation to formic acid.The interfacial modification between Fe_(2)O_(3)semiconductor and Ni(OH)xcocatalyst with ultrathin TiO_(x) interlayer not only improved the photocurrent density by accelerating the kinetics of photogenerated charge carriers,but also kept the high Faradaic efficiency(over 95% in 30 h) towards the value-added formic acid product.This work proposes an effective method to promote the PEC activity and enhance the long-term stability of photoelectrodes for upcycling PET plastic wastes.

金属卤化物钙钛矿光电材料和器件

2009年ABX_(3)钙钛矿晶型的甲胺铅卤CH_(3)NH_(3)PbX_(3)(X=I、Br、Cl)钙钛矿材料首次应用于太阳能电池,但初始报道效率低、稳定性差。2012年后,可溶液法制备的钙钛矿太阳能电池凭借其吸光系数高、激子结合能低等优点,迅速表现出低成本和高效率的突出优势,并在光电器件等交叉领域具有很强的应用潜力。因此,钙钛矿太阳能电池被Science杂志评为2013年度国际十大科技进展,是化学和材料领域特别是光伏领域新兴的变革性技术之一。钙钛矿太阳能电池材料与器件的发展一直面临大面积、高效率、稳定性和环境友好性等挑战,对应的是钙钛矿晶体可控生长、缺陷钝化、器件优化材料稳定性和铅毒性等科学问题。

Prognostic value of preoperative prognostic nutritional index and its associations with systemic inflammatory response markers in patients with stage Ⅲ colon cancer

Background: The prognostic nutritional index(PNI) has been widely applied for predicting survival outcomes of patients with various malignant tumors. Although a low PNI predicts poor prognosis in patients with colorectal cancer after tumor resection, the prognostic value remains unknown in patients with stage Ⅲ colon cancer undergoing curative tumor resection followed by adjuvant chemotherapy. This study aimed to investigate the prognostic value of PNI in patients with stage III colon cancer.Methods: Medical records of 274 consecutive patients with stage Ⅲ colon cancer undergoing curative tumor resection followed by adjuvant chemotherapy with oxaliplatin and capecitabine between December 2007 and December2013 were reviewed. The optimal PNI cutoff value was determined using receiver operating characteristic(ROC) curve analysis. The associations of PNI with systemic inflammatory response markers, including lymphocyte-to-monocyte ratio(LMR), neutrophil-to-lymphocyte ratio(NLR), platelet-to-lymphocyte ratio(PLR), and C-reactive protein(CRP)level, and clinicopathologic characteristics were assessed using the Chi square or Fisher's exact test. Correlation analysis was performed using Spearman's correlation coefficient. Disease-free survival(DFS) and overall survival(OS)stratified by PNI were analyzed using Kaplan-Meier method and log-rank test, and prognostic factors were identified by Cox regression analyses.Results: The preoperative PNI was positively correlated with LMR(r= 0.483, P < 0.001) and negatively correlated with NLR(r =-0.441, P < 0.001), PLR(r =-0.607, P < 0.001), and CRP level(r =-0.333, P < 0.001). A low PNI(≤49.22)was significantly associated with short OS and DFS in patients with stage ⅢC colon cancer but not in patients with stage ⅢA/ⅢB colon cancer.In addition, patients with a low PNI achieved a longer OS and DFS after being treated with6-8 cycles of adjuvant chemotherapy than did those with < 6 cycles. Multivariate analyses revealed that PNI was independently associated with DFS(hazard ratios 2.001; 95% confidence interval 1.157-3.462; P = 0.013).Conclusion: The present study identified preoperative PNI as a valuable predictor for survival outcomes in patients with stage Ⅲ colon cancer receiving curative tumor resection followed by adjuvant chemotherapy.

Dynamic tensile behaviour and crack propagation of coal under coupled static-dynamic loading

The fracture behaviour and crack propagation features of coal under coupled static-dynamic loading conditions are important when evaluating the dynamic failure of coal.In this study,coupled static-dynamic loading tests are conducted on Brazilian disc(BD)coal specimens using a modified split Hopkinson pressure bar(SHPB).The effects of the static axial pre-stress and loading rate on the dynamic tensile strength and crack propagation characteristics of BD coal specimens are studied.The average dynamic indirect tensile strength of coal specimens increases first and then decreases with the static axial pre-stress increasing.When no static axial pre-stress is applied,or the static axial pre-stress is 30%of the static tensile strength,the dynamic indirect tensile strength of coal specimens shows an increase trend as the loading rate increases.When the static axial pre-stress is 60%of the static tensile strength,the dynamic indirect tensile strength shows a fluctuant trend as the loading rate increases.According to the crack propagation process of coal specimens recorded by high-speed camera,the impact velocity influences the mode of crack propagation,while the static axial pre-stress influences the direction of crack propagation.The failure of coal specimens is a coupled tensile-shear failure under high impact velocity.When there is no static axial pre-stress,tensile cracks occur in the vertical loading direction.When the static axial pre-stress is applied,the number of cracks perpendicular to the loading direction decreases,and more cracks occur in the parallel loading direction.

Ⅲ期结肠癌患者术前预后营养指数的预后价值及其与全身炎症反应标志物的相关性

背景与目的预后营养指数(prognostic nutritional index,PNI)已广泛应用于预测各种恶性肿瘤患者的生存结局。虽然低PNI预测肿瘤切除后的结直肠癌患者的预后不良,但对接受根治性肿瘤切除术后辅助化疗的Ⅲ期结肠癌患者的预后价值仍未知。本研究旨在探讨PNI对Ⅲ期结肠癌患者的预后价值。方法本文回顾了2007年12月至2013年12月期间,274例接受根治性肿瘤切除术后接受奥沙利铂和卡培他滨辅助化疗的Ⅲ期结肠癌的连续患者的医疗记录。采用受试者工作特征(receiver operating characteristic,ROC)曲线分析确定最佳PNI临界值。采用卡方检验或Fisher’s精确检验评估PNI与全身炎症反应标志物[包括淋巴细胞与单核细胞比值(lymphocyte-to-monocyte ratio,LMR)、中性粒细胞与淋巴细胞比值(neutrophil-to-lymphocyte ratio,NLR)、血小板与淋巴细胞比值(platelet-to-lymphocyte ratio,PLR)、C反应蛋白(C-reactive protein,CRP)水平]和临床病理特征的相关性。采用Spearman’s相关系数进行相关分析。采用Kaplan-Meier法和log-rank检验分析PNI分层的无病生存期(disease-free survival,DFS)和总生存期(overall survival,OS),并通过Cox回归分析确定预后因子。结果术前PNI与LMR呈正相关(r=0.483,P <0.001),与NLR(r=-0.441,P <0.001)、PLR(r=-0.607,P <0.001)和CRP水平(r=-0.333,P <0.001)呈负相关。在ⅢC期结肠癌患者中,低PNI(≤49.22)与短OS和DFS显著相关,而在ⅢA/ⅢB期结肠癌患者中则不相关。此外,在PNI低的患者中,接受6–8个疗程辅助化疗的患者比接受<6个疗程治疗的患者获得了更长的OS和DFS。多变量分析显示PNI与DFS独立相关(风险比=2.001;95%置信区间:1.157–3.462;P=0.013)。结论术前PNI是接受根治性肿瘤切除术后辅助化疗的Ⅲ期结肠癌患者生存结局的重要预测指标。

A review of mechanism and prevention technologies of coal bumps in China

Coal bump refers to a sudden catastrophic failure of coal seam and usually can cause serious damages to underground mining facilities and staff. In this circumstance, this paper focuses on the recent achievements in the mechanism and prevention techniques of coal bumps over the past five years in China.Based on theoretical analysis, laboratory experiment, numerical simulation and field test, the characteristics of coal bumps occurrence in China's coal mines were described, and the difference between coal bumps and rockbursts was also discussed. In addition, three categories of coal bumps induced by'material failure' were introduced, i.e. hard roof, floor strata and tectonic structures, in which the mechanism of coal bumps induced by geological structures was analyzed. This involves the bump liability and microstructure effects on bump-prone coal failure, the mechanism of coal bumps in response to fault reactivation, island face mining or hard roof failure. Next, the achievements in the monitoring and controlling methods of coal bumps were reviewed. These methods involve the incorporated prediction system of micro-seismicity and mining-induced pressure, the distributed micro-seismic monitoring system, energy absorption support system, bolts with constant resistance and large elongation,and the 'multi-stage' high-performance support. Finally, an optimal mining design is desirable for the purpose of coal bump mitigation.

Dynamic failure risk of coal pillar formed by irregular shape longwall face:A case study

Irregular shape workface would result in the presence of coal pillar, which leads to high stress concentration and possibly induces coal bumps. In order to study the coal bump mechanism of pillars, static and dynamic stress overlapping(SDSO) method was proposed to explain the impacts of static stress concentration and tremors induced by mining activities. The stress and deformation in surrounding rock of mining face were analyzed based on the field case study at 1303 workface in Zhaolou Coal Mine in China.The results illustrate that the surrounding rock of a workface could be divided into four different zones,i.e., residual stress zone, stress decrease zone, stress increase zone and original stress zone. The stress increase zone is prone to failure under the SDSO impact loading conditions and will provide elastic energy for inducing coal bump. Based on the numerical modelling results, the evolution of static stress in coal pillar as the size of gob increasing was studied, and the impact of dynamic stress was investigated through analyzing the characteristics of tremor activities. The numerical results demonstrate the peak value of vertical stress in coal pillar rises from about 30 MPa with mining distance 10 m to 52.6 MPa with mining distance 120 m, and the location of peak stress transfers to the inner zone of coal pillars as the workface moves forward. For the daily tremor activities, tremors with high energy released indicate high dynamic stress disturbance on the surrounding rock, therefore, the impact of dynamic stressing is more serious during workface extension period because the tremor frequency and average energy after workface extension are higher than those before the workface extension.

Recent advances in interlayer and separator engineering for lithium-sulfur batteries

Lithium-sulfur(Li-S)batteries have great potential in next-generation energy storage due to its high theoretical specific capacity and energy density.However,there are several challenges to the practical application of Li-S batteries including the growth of lithium dendrites and the shuttle effect of polysulfide.Introducing interlayeres(freestanding or coated on the separator)is an effective approach to reduce these obstacles and improve the electrochemical performance of Li-S batteries.In this review,we briefly summarize the interlayer materials and structures modified on both cathodic and anodic sides including(ⅰ)carbon-based materials,(ⅱ)polymers,(ⅲ)inorganic metal compounds,(iv)metal-organic frameworks,as well as(v)the novel separators in recent years.We also systematically address the fabrication processes,assembling methods,and functions of interlayers for enhancing the performance of Li-S batteries.Furthermore,the prospects and outlooks of the future development of advanced interlayers and separators are also presented.

Shear Induced Seepage and Heat Transfer Evolution in a Single-Fractured Hot-Dry-Rock

In the enhanced geothermal system(EGS),the injected fluid will induce shear sliding of rock fractures(i.e.,hydroshearing),which consequently,would increase the fracture aperture and improve the heat transfer efficiency of the geothermal reservoir.In this study,theoretical analysis,experimental research and numerical simulation were performed to uncover the permeability and heat transfer enhancement mechanism of the Hot-Dry-Rock(HDR)mass under the impact of shearing.By conducting the direct shear test with the fractured rock samples,the evolution process of fracture aperture during the shearing tests was observed,during which process,cubic law was adopted to depict the rock fracture permeability.To investigate the seepage characteristics and temperature distribution of the fractured HDR under the influence of shearing,a simulation study of shear-seepage-heat transfer in a fractured rock mass has been conducted to validate the observed shear-induced fracture dilation during the direct shear test.The results demonstrate that(1)the hydroshearing increases the dilation of granite fracture and enhances the permeability of the HDR rock mass,while the temperature around the HDR fracture will reduce.(2)Fracture roughness is of vital importance to enhance the permeability during the shearing tests.To be more specific,a rougher fracture always implies a higher permeability and a greater heat extraction efficiency.(3)The shear induced heat extracting efficiency is dominated by the increased fluid flux in the earlier period of the EGS reservoir,and this efficiency is controlled by the outlet water temperature since the fluid flux becomes stable after the shearing test.Therefore,balancing the hydroshearing enhanced heat extraction efficiency and EGS reservoir lifespan would be significant to the sustainable development and utilization of geothermal energy.

Stabilizing the MAPbI3 perovksite via the in-situ formed lead sulfide layer for efficient and robust solar cells

Surface passivation via post-treatment with organic reagents is a popular strategy to improve the stability and efficiency of perovskite solar cell. However, organic passivation still suffers from the weak bonding between organic chemicals and perovskite layers. Here we reported a facile inorganic layer passivating method containing strong Pb–S bonding by using ammonium sulfide treatment. A compact PbS_x layer was in-situ formed on the top surface of the perovskite film, which could passivate and protect the perovskite surface to enhance the performance and stability. Our novel inorganic passivation layer strategy demonstrates great potential for the development of high efficiency hybrid and robust perovskite optoelectronics.

Characteristic strength and acoustic emission properties of weakly cemented sandstone at different depths under uniaxial compression

As coal mining is extended from shallow to deep areas along the western coalfield,it is of great significance to study weakly cemented sandstone at different depths for underground mining engineering.Sandstones from depths of 101.5,203.2,317.3,406.9,509.9 and 589.8 m at the Buertai Coal Mine were collected.The characteristic strength,acoustic emission(AE),and energy evolution of sandstone during uniaxial compression tests were analyzed.The results show that the intermediate frequency(125-275 kHz)of shallow rock mainly occurs in the postpeak stage,while deep rock occurs in the prepeak stage.The initiation strength and damage strength of the sandstone at different depths range from 0.23 to 0.50 and 0.63 to 0.84 of peak strength(σ_(c)),respectively,decrease exponentially and are a power function with depth.The precursor strength ranges from 0.88σ_(c)to 0.99σ_(c),increases with depth before reaching a depth of 300 m,and tends to stabilize after 300 m.The ratio of the initiation strength to the damage strength(k)ranges from 0.25 to 0.62 and decreases exponentially with depth.The failure modes of sandstone at different depths are tension-dominated mixed tensile-shear failure.Shear failure mainly occurs at the unstable crack propagation stage.The count of the shear failure bands before the peak strength increases gradually,and increases first and then decreases after the peak strength with burial depth.The cumulative input energy,released elastic energy and dissipated energy increase with depth.The elastic release rate ranges from 0.46×10^(-3)to 198.57×10^(-3)J/(cm^(3)s)and increases exponentially with depth.

Synergistic stabilization of CsPbI_(3) inorganic perovskite via 1D capping and secondary growth

Cesium lead iodide(CsPbI_(3)) perovskite has gained great attention in the photovoltaic(PV) community because of its unique optoelectronic properties, good chemical stability and appropriate bandgap for sunlight harvesting applications. However, compared to solar cells fabricated from organic-inorganic hybrid perovskites, the commercialization of devices based on all-inorganic CsPbI_(3) perovskites still faces many challenges regarding PV performance and long-term stability. In this work, we discovered that tetrabutylammonium bromide(TBABr) post-treatment to CsPbI_(3) perovskite films could achieve synergistic stabilization with both TBA+cation intercalation and Br-doping. Such TBA^(+) cation intercalation leads to onedimensional capping with TBAPb I3 perovskite formed in situ, while the Br-induced crystal secondary growth helps effectively passivate the defects of CsPbI_(3) perovskite, thus enhancing the stability. In addition, the incorporation of TBABr can improve energy-level alignment and reduce interfacial charge recombination loss for better device performance. Finally, the highly stable TBABr-treated CsPbI_(3)-based perovskite solar cells show reproducible photovoltaic performance with a champion efficiency up to 19.04%, while retaining 90% of the initial efficiency after 500 h storage without encapsulation.

Inorganic CsPbI3 Perovskites toward High-Efficiency Photovoltaics

The organic–inorganic hybrid perovskite solar cells(PSCs)have demonstrated their unprecedented high efficiency and potential for commercialization.The volatile organic components in the hybrid perovskite crystal structure are still a big challenge for long-term stabilities.Recently,inorganic CsPbI3 perovskite has attracted much attention because of its superior chemical stability over the prevailing hybrid organic–inorganic perovskite and the most suitable band gap among all-inorganic perovskites.Nevertheless,CsPbI3 suffers from phase instability and low photovoltaic(PV)performance due to its undesirable tolerant factor.Much research effort has been devoted into stabilization of CsPbI3.In this perspective,we review the recent progress on chemical engineering processes for the stabilization of inorganic CsPbI3 perovskite for high-efficiency PVs.We also discuss the importance of understanding mechanism behind stabilization of CsPbI3 perovskite film and the development of inorganic CsPbI3-based highly efficient and stable PSCs.

Cs-content-dependent organic cation exchange in FA1-xCsxPbI3 perovskite

FA-Cs mixed-cation perovskite has been reported as a promising candidate for obtaining highly efficient and stable photovoltaic devices.Phenylethylamine iodide(PEAI)post-treatment is a widely used and effective method for surface passivation of FA-Cs perovskite layer in devices.However,it is still controversial whether the PEAI post-treatment would form two-dimensional(2D)perovskite PEA_(2)PbI_(4) capping layer or just result in PEA+terminated surface.Here in this work,the function of PEAI post-treatment on FA-Cs mixed-cation perovskite FA_(1-x)Cs_(x)PbI_(3)(x=0.1–0.9)with varied Cs contents is elucidated.With increased Cs content,the FA-Cs perovskite shows higher resistance to the cation exchange between FA+and PEA+.This Cs-content-dependent cation exchange results in the different PEAI reaction preferences with FA-Cs mixed-cation perovskites.Furthermore,higher Cs content with stronger resistance to cation exchange reaction leads to a wider processing window for post-treatment and defect passivation,which is beneficial for the fabrication of large-scale photovoltaic devices.

Coupled hydro-mechanical evolution of fracture permeability in sand injectite intrusions

Sandstone“injectite”intrusions are generally developed by the fluidization of weakly cemented sandstones and their subsequent injection into fractured reservoirs.In this work,a continuum coupled hydromechanical model TOUGH-FLAC3D is applied to simulate the discrete fracture network in large-scale sand injectite complexes.A sand production constitutive model is incorporated to consider the formation of sand through plastic deformation and its influence on evolution of fracture permeability.Overpressures in the fluidized sand slurry drives the injection with sand dikes intruded upwards,typically into previously low permeability“tight”mudstone formations.The contrast in poroelastic properties of the underlying weak sandstone and overlying injectite receptor directly affects the evolution of fracture aperture both during and after intrusion.Fluid drainage into the unconsolidated matrix may reduce the extent of fracture aperture growth,through the formation of shear bands.The results of this work have broad implications related to the emplacement of sandstone intrusions and subsequent hydrocarbon accumulation,maturation and then production.

Recent Progress in Large-Area Perovskite Photovoltaic Modules

Perovskite solar cells(PSCs)have undergone a dramatic increase in laboratory-scale effi ciency to more than 25%,which is comparable to Si-based single-junction solar cell effi ciency.However,the effi ciency of PSCs drops from laboratory-scale to large-scale perovskite solar modules(PSMs)because of the poor quality of perovskite fi lms,and the increased resistance of large-area PSMs obstructs practical PSC applications.An in-depth understanding of the fabricating processes is vital for precisely controlling the quality of large-area perovskite fi lms,and a suitable structural design for PSMs plays an impor-tant role in minimizing energy loss.In this review,we discuss several solution-based deposition techniques for large-area perovskite fi lms and the eff ects of operating conditions on the fi lms.Furthermore,diff erent structural designs for PSMs are presented,including the processing technologies and device architectures.

A mixed-cation lead iodide MA_(1-x)EA_xPbI_3 absorber for perovskite solar cells

The mixed-cation lead halide perovskites have emerged as a new class of promising light harvesting materials for solar cells. The formamidinium（FA）, methylammonium（MA） and Cs cations are widely studied in the field of mixed-cation perovskites. Here, we have investigated ethylammonium（EA） as an alternative cation to fabricate a mixed-cation perovskite of MA_（1-x）EA_xPbI_3. We have characterized the materials using the X-ray diffraction（XRD）, scanning electron microscope（SEM）, and UV–vis spectrum. Our results have confirmed the successful incorporation of EA cations into MAPbI_3. Interestingly, the optimal amount of EA to achieve the best performance is quite low. This is different from the FA–MA mixed-cation perovskites although EA and FA have similar radii. In short, the EA–MA mixed-cation perovskite has some material and device properties highly distinguishable from the FA–MA one.

Real-time pore structure evolution difference between deep and shallow coal during gas adsorption:A study based on synchrotron radiation small-angle X-ray scattering

Coal seam CO_(2) sequestration is an important option to address global warming.A better knowledge on coal pore structure evolution during gas adsorption can provide guidance for coal seams CO_(2) seques-tration.However,few investigations on the pore structure evolution differences between the deep and shallow coal were conducted during gas adsorption.In this study,based on the real-time synchrotron radiation small-angle X-ray scattering(SAXS)observation,the average pore diameter and pore surface fractal dimension evolution differences between deep and shallow coal were investigated from the as-pects of coal compositions and stress history.Two types of coal deformation(inner-swelling and outer-swelling)coexist during gas adsorption.Coal compositions have significant impact on the dominance of deformation type.The dominance of inner-swelling in deep coal is induced by the higher ash contents,and there is the decrease of average pore diameter during gas adsorption.The impact of stress-history(burial depth)on adsorption-induced deformation is more prominent than that of gas adsorption ca-pacity.In deep coal,the surface fractal dimension evolution presents a negative correlation with the evolution of pore diameters.In shallow coal,the surface fractal dimension evolution presents a Langmuir-type correlation with the adsorption time.

Organic ligand nanoarchitectonics for BiVO_(4) photoanodes surface passivation and cocatalyst grafting

Bismuth vanadate(BiVO_(4))is a promising photoanode material for efficient photoelectrochemical(PEC)water splitting,whereas its performance is inhibited by detrimental surface states.To solve the problem,herein,a low-cost organic molecule 1,3,5-benzenetricarboxylic acid(BTC)is selected for surface passivation of BiVO_(4) photoanodes(BVOs),which also provides bonding sites for Co^(2+)to anchor,resulting in a Co-BTC-BVO photoanode.Owing to its strong coordination with metal ions,BTC not only passivates surface states of BVO,but also provides bonding between BVO and catalytic active sites(Co^(2+))to form a molecular cocatalyst.Computational study and interfacial charge kinetic investigation reveal that chemical bonding formed at the interface greatly suppresses charge recombination and accelerates charge transfer.The obtained Co-BTC-BVO photoanode exhibits a photocurrent density of 4.82 mA/cm^(2) at 1.23 V vs.reversible hydrogen electrode(RHE)and a low onset potential of 0.22 VRHE under AM 1.5 G illumination,which ranks among the best photoanodes coupled with Co-based cocatalysts.This work presents a novel selection of passivation layers and emphasizes the significance of interfacial chemical bonding for the construction of efficient photoanodes.