Home > Fabrication of Α-Hematite/Ferrite Composite Thin Films on Planar and Three-Dimensional Nanostructured Substrates for Photoelectrochemical Water Splitting
Fabrication of Α-Hematite/Ferrite Composite Thin Films on Planar and Three-Dimensional Nanostructured Substrates for Photoelectrochemical Water Splitting
Inspired from the natural photosynthesis in which solar radiation is being effectively utilized in photoconversion of simple compounds (H2O and CO2) into carbohydrates and oxygen, scientists are dragged toward artificial photosynthesis for obtaining important chemicals from cheap and sustainable sources. The efficient conversion of solar energy into clean form chemical energy is the concept that is considered to be effective solution of world’s growing issues i.e. increasing demand of the fossil fuels and global warming. Hydrogen is considered as the fuel of the future because it has more energy capacity than fossil fuel, yielding zero carbon emission and has competency to replace the fossil fuels being used in different sectors. Photoelectrochemical (PEC) splitting of water is considered as one of the most promising technology by which solar energy could be efficiently utilized in hydrogen generation from its cheap and abundantly available source i.e. water. In this work, we focussed on the use of α-hematite/ferrites composite thin films as electrode material for photoelectrochemical water oxidation. Based on the band gap and their band alignment knowledge, three different series of composite thin films i.e. (1) CuFe2O4/α-Fe2O3, (2) ZnFe2O4/α-Fe2O3 and (3) NiFe2O4/ α-Fe2O3 were deposited on planar and 3-dimentional (3-D) nanostructured substrates. The fabricated devices were then structurally and morphologically characterized by various techniques and evaluated for photoelectrochemical water oxidation applications. It has confirmed that the ratio between the components of the composite thin films is crucial, so the highest activity results were obtained by the thin films devices having equal molar ratio (1:1) between α-hematite and ferrites in all the three classes. Among CuFe2O4/α-Fe2O3 composite thin films series, the CF-1, having 1:1 molar ratio between CuFe2O4 and α-Fe2O3 showed the highest activity. This composite when deposited on planar FTO coated substrate showed the highest photocurrent density of 1.24 mA/cm2 at the applied voltage of 1.23 VRHE and retained the photoconversion efficiency of 0.14%. The same material when deposited on 3-D nanostructured substrate, an increase in the photocurrent density upto 2.2 mA/cm2 at the same applied voltage was recorded. Among ZnFe2O4/α-Fe2O3 composite thin films, we found that nanostructured device (ZF1-NSP) having molar ratio of 1:1 between their components retained the highest photocurrent density of 2.19 mA/cm2 and showed the photoconversion efficiency of 0.22%. This photocurrent density is 3.4 and 2.73 times higher than photocurrent density values of pure hematite on planar FTO and the highest reported value of ZnFe2O4/α-Fe2O3 composite, respectively. Among NiFe2O4/α-Fe2O3 composite thin films, the highest photocurrent density of 2.1 mA/cm2 at 1.23 VRHE was obtained for the composite device having 1:1 molar ratio of NiFe2O4/α-Fe2O3 iii deposited on 3-D nanostructured substrate (NF1-NSP), which was 3.3 times more photocurrent density than pure hematite. It has been verified by electrochemical impedance spectroscopy (EIS) that α-hematite/ferrite composite thin films have greater conductivities of charge carriers than α-hematite and the highest values of charge conductivities were obtained for the composites consisting of equal molar ratio between α-hematite and ferrite. Based on photoluminescence studies, the photogenerated charge recombination has also been decreased by increasing ferrite component in α-hematite/ferrite composite. So, the better activities of α-hematite/ferrite composite in PEC water oxidation is provided by greater electrical conductivity and reduced charged recombination as compared to pure α-hematite. The performance of 3-D nanostructured devices in photoelectrochemical water oxidation were much greater than planar devices with the similar composite thin films. The three dimensional architecture of the electrode offers large surface area for the redox reaction and larger capability to harvest visible light for enhancing the performance of 3-D nanostructured electrode as compared to planar electrode.
مولانا مفتی عتیق الرحمن ۱۲؍ مئی ۸۴ء کو ہندوستان کے نامور عالم مولانا مفتی عتیق الرحمن فالج کے موذی مرض میں ایک طویل مدت تک مبتلا رہ کر ۸۴ سال کی عمر میں اس دارفانی سے رحلت گراے عالمِ جاودانی ہوئے۔ ان کے اس مرض کی المناکی دارالمصنفین سے بھی بڑی حد تک وابستہ ہے، اس لئے اس ادارہ کے خدام ان کی وفات حسرت آیات سے بہت سوگوار ہیں، فروری ۱۹۸۲ء میں یہاں ’’اسلام اور مستشرقین‘‘ پر جو سیمینار ہوا تھا، اس میں وہ شرکت کے لئے تشریف لائے تھے، تین روز یہاں بہت ہنسی خوشی سے گذارے، اس کے ایک اجلاس کی صدارت بھی کی، خوش خوش یہاں سے اور شرکاء کے ساتھ روانہ ہوئے تو ریل ہی میں بارہ بنکی کے پاس ان پر فالج کا سخت حملہ ہوا، ان کے ہم سفر مولانا سعید احمد اکبر آبادی اور مولانا سجاد حسین نے ان کو کسی طرح لکھنؤ کے ہسپتال میں داخل کیا، ان کی طبیعت کچھ سنبھلی تو پھر دہلی لے جائے گئے، اس وقت سے اپنی وفات تک تقریباً سوا دو سال تک بستر ہی پر رہے، خیال ہوتا ہے کہ وہ دارالمصنفین کا سفر نہ کرتے تو اس موذی مرض میں مبتلا نہ ہوتے، مگر مشیتِ ایزدی یہی تھی، راقم ان کی عیادت کے لئے کئی بار ان کی خدمت میں حاضر ہوا ان کا جسم تو بیکار ہوچکا تھا، مگر دماغ بیدار رہا، گفتگو میں وہی روانی اور شیر ینی ہوتی جو ان کی طبیعت کا مخصوص رنگ تھا، ہر قسم کے مسائل پر گفتگو کرتے، مگر زیادہ تر دارالعلوم دیوبند کے قضیۂ نامرضیہ پر اظہار خیال کرتے، ایسا معلوم ہوتا کہ وہاں کا المیہ پیش نہ آتا تو اس مرض میں مبتلا نہ ہوتے اور ہوتے بھی تو اتنے دنوں تک بستر علالت پر پڑے نہ رہتے، دارالعلوم دیوبند...
The patience is the noblest virtue and lays great stress on being patient. Islamic History is full of the examples from the lives of Ṣaḥabah who sacrificed a lot. Islam delineates all the divers and broader aspects of patience in all its form. The need is to follow all these noble personalities called Ṣaḥabah in our lives in this era in order to show tolerance and give respect to others. The Prophetic era is considered as the golden period wherein great students were trained to teach humanity, courage and determination. Although, having low status in society they taught the world how to lead a purposeful life with good morals and distinctive principles. They were the men rightly guided with high and far-seeing vision of the Prophet (r). They were the oceans of knowledge, instilled with spirit of service, thus stood as the exemplary icons of practical life. They chose indigent and destitute life but never extended their hands for help for their highly esteemed self-reliance. Those were men of field who never got afraid of anything in their life. They faced all the challenges with faith and patience, and with the spirit of Jihad, they crushed the infidels and uprooted infidelity from Arabian Peninsula. Owing to their strong faith, they passed through many wild, menacing and brutal stages but never tilted towards the worldly things or people, nor did they compromised on their firm belief and clear stance cultivated by the Holly Prophet (r). This was the reason they got the title weak those about is article This. Allah Almighty from (رضي الله عنهم) of companions of the Prophet (r) who were icons of Patience and determination. Their patience is un-exemplary. They were gifted with excellent qualities of forbearance.
Computations of Compressible Two-Phase Flow Models Two-phase flow is generally understood as being a simultaneous flow of two different im- miscible phases separated by an infinitesimal thin interface. Phases are identified as ho- mogeneous parts of the fluid for which unique local state and transport properties can be defined. In most cases, phases are simply referred to as the state of matter, e.g. gas/vapor, liquid, or solid. Typical examples are the flow of liquid carrying vapor or gas bubbles, or the flow of gas carrying liquid droplets or solid particles. However, more complex flow pro- cesses may exist where the phase distribution is less well defined. This work is concerned with the numerical approximation of homogenized two-phase flow models. The models are obtained by averaging the balance laws for single phases and are non-strictly hyperbolic and non-conservative, i.e. they are not expressible in divergence form. The seven-equation two-phase models are regarded as well-established and can be applied to study various two- phase flow phenomena. However, physical and numerical difficulties are associated with these models. In most situations, the general physics of the models is not needed, thus, more compact models may be enough. For that reason, the reduced five- and six-equation models, deduced from the seven-equation models, are investigated in this dissertation. The five-equation model is obtained under the asymptotic limit of stiff velocity and pressure re- laxations, while the six-equation model assumes stiff velocity relaxation only. Our primary objective is to develop a deeper understanding of these models containing non-conservative derivatives and to numerically approximate them. The high order kinetic flux-vector split- ting (KFVS) scheme, the space-time conservation element and solution element (CESE) method, the high resolution central schemes, and the HLLC-type Riemann solvers are ap- plied to solve these models. Several test problems are carried out for all considered models and the numerical results of suggested schemes are compared with each other and with those available in the literature.