The multifunctional tixw1 xo2 (x=0 5; 0 6; 0 7; 0 8) support for platinum to enhance the activity and co tolerance of direct alcohol fuel cells

VIET NAM NATIONAL UNIVERSITY HO CHI MINH CITY HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY HAU QUOC PHAM THE MULTIFUNCTIONAL TixW1-xO2 (x = 0.5; 0.6; 0.7; 0.8) SUPPORT FOR PLATINUM TO ENHANCE THE ACTIVITY AND CO-TOLERANCE OF DIRECT ALCOHOL FUEL CELLS A dissertation submitted for the degree of Doctor of Philosophy HO CHI MINH CITY – 2022 VIET NAM NATIONAL UNIVERSITY HO CHI MINH CITY HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY HAU QUOC PHAM THE MULTIFUNCTIONAL TixW1-xO2 (x = 0.5; 0.6; 0.7; 0.8) SUPPORT FOR PLATINUM TO ENHANCE THE ACTIVITY AND CO-TOLERANCE OF DIRECT ALCOHOL FUEL CELLS A dissertation submitted for the degree of Doctor of Philosophy Major subject: Chemical Engineering Major subject code: 9520301 Independent Reviewer: Independent Reviewer: Reviewer: ASSOC PROF DR TRAN VAN MAN Reviewer: ASSOC PROF DR NGUYEN DINH THANH Reviewer: ASSOC PROF DR NGUYEN NHI TRU Advisor: ASSOC PROF VAN THI THANH HO ASSOC PROF SON TRUONG NGUYEN PLEDGE I pledge that this dissertation is my study under the direct guidance of Assoc Prof Van Thi Thanh Ho and Assoc Prof Son Truong Nguyen The study results and conclusions in this dissertation are honest, and not copied from any one source and in any form The reference to the sources of documents (if any) has been cited and the reference sources are recorded as prescribed Signature Hau Quoc Pham i ABSTRACT The worldwide environment has been getting worse day by day because of the emission of various harmful pollutants into the environment from burning traditional fossil fuels Also, fossil fuels are limited resources and will be exhausted in the next few decades, therefore, finding out sustainable and renewable energy sources has sparked interest as future alternatives Recently, direct alcohol fuel cells (DAFCs) have been considered a promising green energy source in portable and transportation applications due to their relatively simple infrastructure, portability, operation cost, easy storage, and conveyance of alcohol fuels Nonetheless, the sluggish oxidation kinetics and “CO-like poisoning” effect of catalysts are limitations for commercializing DAFCs Alloying Pt with Ru is regarded as an efficient anodic DAFC catalyst owing to its high electrochemical activity and great CO anti-poisoning ability The Ru metal, however, can be dissolved at the fuel cell operation potential, resulting in a decrease in the electrocatalytic stability of this alloy catalyst Furthermore, the high price and low natural abundance of Ru are drawbacks of particular uses To address aforementioned problems, we fabricate TixW1-xO2 (x = 0.5; 0.6; 0.7; 0.8) nanostructures as multifunctional support with co-catalytic functionality to prevent or reduce the deterioration of anodic catalyst in DAFCs Additionally, tuning morphology and structure of metal catalyst are also combined to enhance the catalytic performance of electrocatalyst, thereby promoting large-scale DAFC applications Various mesoporous TixW1-xO2 (x = 0.5; 0.6; 0.7; 0.8) supports are fabricated by a facile solvothermal route to comprehend the effect of doping tungsten concentration on electrochemical properties of 20 wt% Pt/TixW1-xO2 catalysts for ethanol electrooxidation reaction (EOR) As a result, the surface area and electrical conductivity of asprepared supports are drastically increased with the doped tungsten contents of 20 at% (Ti0.8W0.2O2) and 30 at% (Ti0.7W0.3O2) With rising the doped tungsten content up to 40 at% (Ti0.6W0.4O2), the electrical conductivity is almost unchanged, whereas the surface area is remarkably decreased This implies that the addition of proper doped tungsten content into TiO2 lattices results in an enormous enhancement in both surface area and electrical conductivity Also, small-size Pt nanoparticles (NPs) are well-distributed on ii the support surface by a rapid microwave-assisted polyol route In term of the EOR, 20 wt% Pt/TixW1-xO2 (x = 0.6; 0.7; 0.8) catalyst shows the catalytic performance better than the commercial 20 wt% Pt/C (E-TEK) catalyst Among as-made catalysts, 20 wt% Pt/Ti0.7W0.3O2 catalyst displays the highest mass activity (260 23 mA mgPt-1) and largest If/Ib ratio (1.34), which are 2.0- and 1.57-fold greater than those of 20 wt% Pt/C (ETEK) catalyst (130.62 mA mgPt-1 for mass activity and 0.85 for If/Ib value, respectively) After 5000-cycling ADT, as-made catalysts show the mass activity loss about twice as lower than the commercial catalyst that exhibits great EOR stability Experimental results demonstrate that TixW1-xO2 supports can be utilized as a suitable alternative for the common carbon material in the function of catalyst support for fuel cells For the first time, a combination of using non-carbon nanosupport and tuning the morphology and structure of metal catalyst is utilized to assemble a robust catalyst for alcohol oxidation reaction (AOR) The one-dimensional (1D) Pt nanowires (NWs) are successfully grown on the Ti0.7W0.3O2 surface by a simple chemical reduction route at room temperature, only using formic acid as a reducing agent These observational results indicate that the 1D Pt NWs/Ti0.7W0.3O2 catalyst is a potential anodic catalyst for the oxidation reaction of methanol (MOR) and ethanol (EOR), which can replace a conventional Pt NPs/C catalyst For instance, 1D Pt NWs/Ti0.7W0.3O2 catalyst exhibits a low onset potential (~0.1 VNHE for MOR and ~0.2 VNHE for EOR), high mass activity (355.29 mA mgPt-1 for MOR and 325.01 mA mgPt-1 for EOR), and impressive electrochemical stability compared to the Pt NPs/C catalyst The outstanding activity and stability of 1D Pt NWs/Ti0.7W0.3O2 catalyst can be interpreted due to the unique properties of 1D Pt nanostructures and advantages of Ti0.7W0.3O2, as well as synergetic effects between 1D Pt NWs and Ti0.7W0.3O2 support More importantly, 1D-bimetallic Pt3Co NWs with a diameter of around nm and several tens of nanometers in the lengths are grown on the Ti07W0.3O2 by a templateand surfactant-free chemical reduction method The 1D-bimetallic Pt3Co NWs/Ti0.7W0.3O2 catalyst exhibits high mass activity (393.29 mA mgPt-1 for MOR and 341.76 mA mgPt-1 for EOR) and great electrochemical durability compared to conventional Pt NPs/C catalyst In addition, the CO-stripping result shows superior CO- iii tolerance of 1D Pt3Co NWs/Ti0.7W0.3O2 catalyst with the COads oxidation peak at 0.64 VNHE, which is much lower than that of the Pt NPs/C catalyst (0.78 VNHE) After 5000cycling ADT, the activity loss of 1D Pt3Co NWs/Ti0.7W0.3O2 catalyst is 10.68% of the initial mass activity, which was 4.18-time lower than that of the Pt NPs/C catalyst (44.66%), indicating superior stability retention of 1D Pt3Co NWs/Ti0.7W0.3O2 catalyst These enhancements are attributable to (i) advantages of 1D nanostructures with abundant active catalytic sites facilitating the oxidation of adsorbed small organic molecules; (ii) addition of Co promotes the removal of strongly bound intermediates on Pt sites neighboring Co, resulting in boosting CO-tolerance of as-prepared catalyst; (iii) synergic and electronic effects of compounds, Pt3Co NWs, and Ti0.7W0.3O2 support This work can open up an effective approach to enhance the performance of catalysts with a decrease in Pt consumption for electrochemical energy conversion iv TÓM T T LU N ÁN Bi n đ i khí h u nhi m môi tr ng th gi i ngày tr nên t i t s phát th i c a ch t ô nhi m t vi c đ t nhiên li u hóa th ch truy n th ng H n n a, tr l ng nghiên li u hóa th ch th gi i gi i h n s c n ki t vài th p k t i, đó, nhu c u tìm ki m ngu n n ng l tái t o đ ng thay th s ch có kh n ng c u tiên Pin nhiên li u s d ng tr c ti p alcohol (DAFCs) đ c nghiên c u s d ng nhi u l nh v c nh v n chuy n thi t b c m tay phát th i khí nhà kính, hi u su t chuy n đ i n ng l ng t ng đ i cao, chi phí v n hành th p, kh n ng l u tr v n chuy n d dàng an toàn c a nhiên li u alcohol Tuy nhiên, đ ng h c cho ph n ng oxi hóa ch m s ng đ c CO c a xúc tác Pt nh ng h n ch nh h ng tr c ti p t i hi u su t ho t đ ng c a DAFCs th i gian ho t đ ng lâu dài V t li u xúc tác h p kim Pt v i Ru đ c s d ng nh xúc tác hi u qu cho ph n ng oxi hóa nhiên li u alcohol ho t tính xúc tác kh n ng ch ng ng đ c CO cao, nh ng s d hòa tan c a kim lo i Ru t i th ho t đ ng c a pin nhiên li u d n t i s không n đ nh c a v t li u xúc tác Ngoài ra, giá thành cao l Ru t nhiên t ng đ i th p c ng m t nh ng c m c a xúc tác Pt-Ru gi i quy t v n đ này, t ng h p kh o sát đ c tính c a v t li u c u trúc nano TixW1-xO2 (x = 0.5; 0.6; 0.7; 0.8) nh v t li u n n xúc tác đa ch c n ng v i vai trò đ ng xúc tác đ c i thi n ho t tính đ b n c a v t li u xúc tác pin nhiên li u s d ng tr c ti p alcohol Ngoài ra, vi c u n hình d ng c u trúc c a kim lo i xúc tác c ng đ c k t h p lu n án đ c i thi n ho t tính xúc tác c a v t li u xúc tác n hóa cho ph n ng oxi hóa alcohol, thúc đ y s ng d ng c a pin nhiên li u s d ng tr c ti p alcohol V t li u n n TixW1-xO2 (x = 0.5; 0.6; 0.7; 0.8) đ nhi t đ kh o sát s nh h ng c a l c t ng h p b ng ph ng pháp dung ng Vonfram (W) pha t p lên đ c tính xúc tác n hóa c a v t li u xúc tác 20 wt% Pt/TixW1-xO2 cho ph n ng oxi hóa ethanol (EOR) K t qu ch r ng di n tích b m t riêng đ d n n c a v t li u n n t ng đáng k l ng W pha t p 20 at% (Ti0.8W0.2O2) 30 at% (Ti0.7W0.3O2), t ng lên t i 40 at% đ d n n h u nh không thay đ i, trog di n tích b m t riêng gi m rõ r t i u ch ng t r ng thêm m t l v ng W pha t p tích h p d n t i s c i thi n c di n tích b m t riêng đ d n n c a v t li u n n TixW1-xO2 Bên c nh đó, h t xúc tác Pt d ng c u v i kích th n n thông qua ph c nh c ng đ c phân b t t b m t v t li u ng pháp polyol có s h tr c a vi sóng i v i EOR, v t li u xúc tác 20 wt% Pt/TixW1-xO2 (x = 0.6; 0.7; 0.8) th hi n hi u qu xúc tác t t h n so v i v t li u xúc tác th ng m i 20 wt% Pt/C (E-TEK) Trong s v t li u xúc tác t ng h p, v t li u xúc tác 20 wt% Pt/Ti0.7W0.3O2 th hi n hoat tính cao nh t v i c ng đ oxi hóa 260 23 mA mgPt-1 t l If/Ib 1.34, g p 1.57 l n so v i xúc tác th wt% Pt/C (E-TEK) (c ng đ oxi hóa 130.62 mA mgPt-1 t l If/Ib 0.85 Sau 5000 vòng quét th tu n hòa, v t li u xúc tác t ng h p đ th p h n kho ng l n so v i xúc tác th c a v t li u t ng h p đ ng m i 20 c cho th y s suy ho t tính ng m i, u cho th y đ b n xúc tác t t c Nh ng k t qu cho th y r ng v t li u n n TixW1-xO2 có th s thay th thích h p cho v t li u carbon th ng m i pin nhiên li u L n đ u tiên, v t li u xúc tác 1D Pt d ng s i (nanowires) đ v t li u n n Ti0.7W0.3O2 b ng ph c t ng h p thành công ng pháp kh đ n gi n t i nhi t đ phòng s d ng formic acid nh ch t kh V t li u xúc tác 1D Pt NWs/Ti0.7W0.3O2 th hi n v t li u xúc tác ti m n ng cho trình oxi hóa methanol (MOR) ethanol (EOR) có th thay th v t li u xúc tác truy n th ng Pt NPs/C C th , xúc tác 1D Pt NWs/Ti0.7W0.3O2 th hi n th kh i phát trình oxi hóa nhiên li u th p (~0.1 VNHE cho MOR ~0.2 VNHE cho EOR), c ng đ oxi hóa cao (355.29 mA mgPt-1 cho MOR 325.01 mA mgPt-1 cho EOR), c ng nh đ b n xúc tác t t so v i v t li u xúc tác Pt NPs/C S c i thi n đ c gi i thích u m c a c u trúc nano 1D Pt v t li u n n Ti0.7W0.3O2 c ng nh hi u ng liên h p gi a 1D Pt NWs v t li u n n Ti0.7W0.3O2 c bi t, xúc tác h p kim 1D Pt3Co d ng s i (NWs) v i đ dài vài ch c nanomet c ng đ ph ng kính kho ng nm c t ng h p thành công v t li u n n Ti0.7W0.3O2 b ng ng pháp kh đ n gi n không s d ng khung m u hay ch t ho t đ ng b m t V t li u xúc tác 1D Pt3Co NWs/Ti0.7W0.3O2 th hi n ho t tính cao (393.29 mA mgPt-1 cho MOR 341.76 mA mgPt-1 cho EOR), đ b n xúc tác t t so v i v t li u xúc tác truy n th ng Pt NPs/C Ngoài ra, ph ng đ c CO v ng pháp CO-stripping th hi n kh n ng ch ng t tr i c a xúc tác 1D Pt3Co NWs/Ti0.7W0.3O2 v i peak oxi hóa COads t i 0.64 VNHE, th p h n đáng k so v i xúc tác Pt NPs/C (0.78 VNHE) Sau 5000 vòng quét vi th tu n hoàn, s suy gi m ho t tính c a v t li u xúc tác 1D Pt3Co NWs/Ti0.7W0.3O2 10.68%, th p h n 4.18 l n so v i xúc tác Pt NPs/C (44.66%), u ch đ b n xúc tác t t c a v t li u 1D Pt3Co NWs/Ti0.7W0.3O2 S c i thi n có th (i) u m c a c u trúc nano 1D v i nhi u v trí ho t hóa thúc đ y q trình oxi hóa phân methanol ethanol; (ii) s xu t hi n c a Co thúc đ y vi c oxi hóa s n ph m trung gian su t q trình oxi hóa nhiên li u b m t Pt, d n t i t ng kh n ng ch ng ng đ CO c a v t li u xúc tác t ng h p; (iii) hi u ng n t liên h p gi a Pt3Co NWs v t li u n n Ti0.7W0.3O2 H ng nghiên c u có th m m t cách ti p c n hi u qu đ nâng cao hi u qu xúc tác c a v t li u xúc tác n hóa v i s gi m l Pt s d ng cho l nh v c chuy n hóa n ng l ng n hóa vii ng ACKNOWLEDGEMENTS First of all, I would like to express my deepest gratitude to my advisors, Assoc Prof Dr Van Thi Thanh Ho, and Assoc Prof Dr Son Truong Nguyen for suggesting the problem, supervising the work, and being a potential source of inspiration at each stage of this dissertation research work I would like to express my deep thankfulness to Prof Nam Thanh Son Phan supported me during this dissertation research work at the University of Technology – Viet Nam University HCMC I would like to give deep thanks to Dr Tai Thien Huynh for the collaboration during years of working together His enthusiasm and support are highly appreciated I would like to thank you for the support of the Faculty of Chemical Engineering – University of Technology – Viet Nam University HCMC, the MANAR Laboratory – Faculty of Chemical Engineering – University of Technology – Viet Nam University HCMC, the Physical Chemistry Laboratory – Ho Chi Minh City University of Natural Resources and Environment, the Applied Physical Chemistry Laboratory – University of Science – Viet Nam University HCMC, and the Key Laboratory of Polymer and Composite Materials – University of Technology – Viet Nam University HCMC My special thanks to my parents, and my girlfriend for understanding, encouragement, and consistent support throughout my dissertation journey Without their enthusiastic support, I could not complete my research Finally, I acknowledge The Young Innovative Science and Technology Incubation Program, managed by Youth Promotion Science and Technology Center, Hochiminh Communist Youth Union, HCMC, Vietnam (Project No 10/2018/H -KHCN-V ), and Ph.D Scholarship Programme of Vingroup Innovation Foundation (VINIF) (No VINIF.2019.TS.22, VINIF.2020.TS.108 and VINIF.2021.TS.016) and University Scholarship of VNU – HCMC, 2019 for financial support I sincerely thank you all! viii ... 9.3 0. 016 48 20 ( 100 wt%) 726 0. 967 Ethanol 97.3 0. 084 62 80 ( 100 wt%) 1367 0. 969 2-Propanol 186.3 0. 107 708 0 ( 100 wt%) 200 5.6 0. 971 8.78 0. 009 5 800 ( 100 wt%) 1189.5 0. 9 90 Ethylene glycol In the. .. reasons, we propose the study entitled: ? ?The Multifunctional TixW1- xO2 (x = 0 .5; 0. 6; 0. 7; 0. 8) Support for Platinum to enhance the activity and CO- tolerance of Direct Alcohol Fuel Cells? ?? This efficient... UNIVERSITY OF TECHNOLOGY HAU QUOC PHAM THE MULTIFUNCTIONAL TixW1- xO2 (x = 0 .5; 0. 6; 0. 7; 0. 8) SUPPORT FOR PLATINUM TO ENHANCE THE ACTIVITY AND CO- TOLERANCE OF DIRECT ALCOHOL FUEL CELLS A dissertation