Carbon Nitride Modified Highly Reduced Graphene as A Potential Photocatalyst For CO2 Reduction: A First-Principle Study. Masters thesis, King Fahd University of Petroleum and Minerals.

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Arabic Abstract

ي يوجلا فلاغلا يف نوبركلا ديسكأ يناث ىوتسم رارتحلاا ثيح نم ربكأ تاديدهت ضرفت يتلا ةيرشبلا ةطشنلأل ةجيتن ةدايزلا يف ( نوبركلا ديسكأ يناثل ةيزيفحتلا لازتخلاا تلاعافت ربتعت .خانملا ريغتو يملاعلا CO2RR فم تاجتنم ىلإ يدؤت يتلا ) ةباذج ةليسو ةدي مامتهلاا نم اريبك اردق يتيفارجلا نوبركلا ديرتينل ةيئوضلا تازفحملا تبذج .يرارحلا سابتحلاا تازاغ نم فيفختلاو نوبركلا مادختسلا ةقاط ببسب قاطنلا ةوجف ةرذ ىلع ديحولا جوزلا ةكراشم ببسب ، صاصتملاا ىلع ةديجلا اهتردقو ةضفخنملا N نرتقم ماظن عم π نم لقانلا تايكيمانيدب قلعتي اميف ةيقرت ىلإ ةجاحب داعبلأا ةيئانث داوملا هذه لازت لا ،كلذ عمو .لوطأ ةقفارتم ةكبشو يعابسلا فراخز ةدلوملا روصلاب ةثحتسملا ةنحشلا تلاماحل يناكملا لصفلا ليهست ىلإ ةفاضلإاب .ةءافك رثكأ يئوض طاشن لجأ نم ،ايئوض ريغ تلاصولل نكمي اجتملا ططخملا تاذ ةسن Z ىوقأ ةيلازتخاو ةدسكؤم تاردق ىلع اضيأ ظفاحت نأ ةبسانملا تلاصوملا هابشأ نم رثكأ وأ نينثا نم ةعونصملا .ايبسن ،انه ةيونانلا حئافصلل يزيفحتلا طاشنلا انفشكتسا g-C3N5 )CN( ( ةياغلل لزتخملا نيفارجلا عم بنج ىلإ ابنج HRG ليلقت وحن ) CO2 ةيرظن ىلع ءانب ( ةيفيظولا ةفاثكلا DFT ليلحتو قاقتشا ايرظن مت ،ةيونانلا داوملا هذه ةردقو ةمءلام ىدم لوح ةبقاث ةرظن باستكلاو .) لثم ،ةيسيئرلا ةيرصبلاو ةينورتكللإا صئاصخلا قاطنلا لكايه ةيئرملا ةعشلأا صاصتماو ،ةيدودحلا ةيئيزجلا تارادملاو ،لمعلا فئاظوو ، هليلحتو ،ةيجسفنبلا قوفو نم قاطنلا ةوجف ضفخنت نأ عقوتملا نم .ةقدب ا 1.8 نم لقأ ىلإ 0.5 تلوف نيب عمجلا دنع HRG و CN ، لدي امم ل لمعلا ةلاد مجح ضفخني .سناجتم ريغ عطاقت نيوكت دنع ايئوض ةدلوملا بوقثلا / تانورتكللإا جاوزأ لصف ةلوهس ىلع g-C3N5 ركبلا ( 5.4 eV ىلإ ) 5.2 eV جمد دنع HRG ، فايطلأا روصت .لضفأ لازتخا ةردق ىلع لوصحلل ةديدجلا ةداملل ىلعأ ليم ىلع لدي امم لاوحت ةاكاحملا ةينورتكللإا  ىصقأ دحب نم 360 ىلإ 540 رتمونان ، ريغ ةلصولا ليدعت دعبو لبق ،ةسناجتملا طمن يف رييغتلا .يلاوتلا ىلع يئوضلا زيفحتلا ءادأ يف ةدايزلا ىلع ليلد وه صاصتملاا قاقتشا مت .ةيونانلا ةبكرملا داوملل CO2RR صاصتما عقاوم( نيتقبط ربع CN و HRG تانيوكتل ) CN-HRG-CO و CN-HRG-COOH ىلع ،يلاوتلا يه ةددحملا تاناكملإا .اهميدقتو ايرظن-0.87 و-0.80 و 0.16 و-0.08 تلوف نأ حضاولا نم كلذل .يلاوتلا ىلع CN-HRG-COOH ناو ضيفخت ةردق اهيدل ل لضفأ ةيئاقت CO2RR ببسب تاقيبطتل ينلاقع لكشب ةلاعف ةيئوض تازفحم ميمصتل ةميق ىؤر جئاتنلا هذه رفوت .دحلا ةضفخنملا اهتاناكمإ CO2RR . ل ةسفانتملا ةيبناجلا تلاعافتلا دحأ CO2RR ( نيجورديهلا روطت لعافت وه HER .) ،كلذل فاشكتسلا اضيأ ةممصملا داوملا مادختسا مت ل ةنكمملا تايللآاو نيجورديهلا صاصتماو صاصتما HER ةبيكرت نأب نيجورديهلا صاصتملا ةبوسحملا ةرحلا ةقاطلا أبنتت . g-C3N5 / HRG 2D / 2D ( ةيتيفارجلا نوبركلا ديرتين ةقبطل زازتملاا عقوم للاخ نم لضفأ لكشب لمعت CN ،) شت دنع ةصاخ مادختساب اهليغ ةيلآ نوكت نأ عقوتملا نم .لينوبركلا تاعومجم Volmer-Heyrovsky HER ىلإ لصي ضفخنم ةقاط زجاح عم دئارلا راسملا يه 0.5 نأ نيح يف هنأ ظحول .نداعملا نم يلاخلا زفحملا اذه لثم مادختساب تلوف CN-HRG-COOH هاجت لضفأ يزيفحت ءادأب عتمتي CO2 RR ، نإف CN-HRG-CO هاجت زاتمم يزيفحت كولس هيدل HER

English Abstract

The level of carbon dioxide in the atmosphere continues to increase as a result of anthropogenic activities which impose greater threats in terms of global warming and climate change. Catalytic reduction reactions of CO2 (CO2RR) leading to useful products are considered an attractive means for carbon utilization and greenhouse gas mitigation. Graphitic carbon nitride photocatalysts have attracted a great deal of interest due to their low band gap energy and good absorption ability, due to the involvement of the lone pair on the N atom with the π-conjugated system of heptazine motifs and a longer conjugated network. However, such two-dimensional materials still need to be upgraded regarding the photo-generated carrier dynamics for more efficient photoactivity. In addition to facilitating the spatial separation of photoinduced charge carriers, Z-scheme hetero junctions made of two or more appropriate semiconductors can also maintain comparatively stronger oxidative and reductive capabilities. Herein, we have explored the catalytic activity of g C3N5 (CN) nanosheets combined with highly reduced graphene (HRG) towards CO2 reduction based on the density functional theory (DFT). To gain insights into the appropriateness and capability of such nanomaterials, key electronic and optical properties, such as band structures, work functions, frontier molecular orbitals, and UV-Vis absorption, were theoretically derived and thoroughly analyzed. The band gap is predicted to drop from 1.8 to less than 0.5 eV upon combining HRG with CN, showing the ease of separation of photogenerated electron/hole pairs as a heterojunction is formed. The magnitude of the work function of pristine g-C3N5 (5.4 eV) xxi decreases to 5.2 eV when HRG is incorporated, which is indicative of a higher tendency of the new material to have a better reduction capability. The simulated electronic spectra depict a shift of max from 360 to 540 nm, before and after the heterojunction modification, respectively. The change in the absorption pattern is evidence of the increase in the photocatalytic performance of the nanocomposite materials. The CO2RR via the two layers (CN and HRG adsorption sites) of CN-HRG-CO and CN-HRG-COOH configurations respectively, have been theoretically derived and presented. The limiting potentials are -0.87, -0.80, -0.16, and -0.08 V respectively. It is therefore evident that CN-HRG-COOH has better reduction capacity and selectivity for CO2RR due to its low limiting potential. These results provide valuable insights for rationally designing effective photocatalysts for CO2RR applications. One of the competing side reactions for CO2RR is the hydrogen evolution reaction (HER). Therefore, the designed materials were also used to explore the adsorption-desorption of hydrogen and possible mechanisms of HER. The computed free energy of hydrogen adsorption predicts that the g-C3N5/HRG 2D/2D combination performs better through the adsorption site of the graphitic carbon-nitride (CN) layer, especially when functionalized with carbonyl groups. The Volmer Heyrovsky HER mechanism is predicted to be the leading pathway with an energy barrier as low as 0.5 eV using such a metal-free catalyst. It was observed that while the CN-HRG-COOH has better catalytic performance towards CO2RR, the CN-HRG-CO has excellent catalytic behavior towards HER.

Item Type:	Thesis (Masters)
Subjects:	Chemistry
Department:	College of Chemicals and Materials > Chemistry
Committee Advisor:	Al-Saadi, Abdulaziz Abdulrahman
Committee Members:	Ganiyu, Saheed Adewale and Al-Sayoud, Abduljabar Qassam
Depositing User:	ABDULRAHEE BELLO (g202216540)
Date Deposited:	31 Dec 2024 08:48
Last Modified:	31 Dec 2024 08:48
URI:	http://eprints.kfupm.edu.sa/id/eprint/143183