As a wide-bandgap semiconductor(WBG), β-Ga_2O_3 is expected to be applied to power electronics and solar blind UV photodetectors. In this review, defects in β-Ga_2O_3 single crystals were summarized, including dislo...As a wide-bandgap semiconductor(WBG), β-Ga_2O_3 is expected to be applied to power electronics and solar blind UV photodetectors. In this review, defects in β-Ga_2O_3 single crystals were summarized, including dislocations, voids, twin, and small defects. Their effects on device performance were discussed. Dislocations and their surrounding regions can act as paths for the leakage current of SBD in single crystals. However, not all voids lead to leakage current. There's no strong evidence yet to show small defects affect the electrical properties. Doping impurity was definitely irrelated to the leakage current. Finally, the formation mechanism of the defects was analyzed. Most small defects were induced by mechanical damages. The screw dislocation originated from a subgrain boundary. The edge dislocation lying on a plane slightly tilted towards the(102) plane, the(101) being the possible slip plane. The voids defects like hollow nanopipes, PNPs, NSGs and line-shaped grooves may be caused by the condensation of excess oxygen vacancies, penetration of tiny bubbles or local meltback. The nucleation of twin lamellae occurred at the initial stage of "shoulder part" during the crystal growth. These results are helpful in controlling the occurrence of crystal defects and improving the device performance.展开更多
A pure phase BaCo_(0.5)Fe_(0.5)O_(3–δ)(BCF),which cannot be obtained before,is successfully prepared in this study by using the calcination method with a rapid cooling procedure.The successful preparation of BCF all...A pure phase BaCo_(0.5)Fe_(0.5)O_(3–δ)(BCF),which cannot be obtained before,is successfully prepared in this study by using the calcination method with a rapid cooling procedure.The successful preparation of BCF allows the evaluation of this material as a cathode for proton-conducting solid oxide fuel cells(H-SOFCs)for the first time.An H-SOFC using the BCF cathode achieves an encouraging fuel cell performance of 2012 mW·cm–2 at 700,two℃-fold higher than that of a similar cell using the classical high-performance Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3–δ)(BSCF)cathode.First-principles calculations reveal the mechanism for the performance enhancement,indicating that the new BCF cathode significantly lowers the energy barriers in the oxygen reduction reaction(ORR)compared with the BSCF cathode.Therefore,improved cathode performance and fuel cell output are obtained for the BCF cell.The fuel cell using the BCF cathode also shows excellent long-term stability that can work stably for nearly 900 h without noticeable degradations.The fuel cell performance and long-term stability of the current BCF cell are superior to most of the H-SOFCs reported in previous reports,suggesting that BCF is a promising cathode for H-SOFCs.展开更多
A La_(0.5)Ba_(0.5)MnO_(3-δ) oxide was prepared using the sol-gel technique.Instead of a pure phase,La_(0.5)Ba_(0.5)MnO_(3-δ) was discovered to be a combination of La_(0.7)Ba_(0.3)MnO_(3-δ) and BaMnO_(3).The in-situ...A La_(0.5)Ba_(0.5)MnO_(3-δ) oxide was prepared using the sol-gel technique.Instead of a pure phase,La_(0.5)Ba_(0.5)MnO_(3-δ) was discovered to be a combination of La_(0.7)Ba_(0.3)MnO_(3-δ) and BaMnO_(3).The in-situ production of La_(0.7)Ba_(0.3)MnO_(3-δ)+BaMnO_(3) nanocomposites enhanced the oxygen vacancy(Vo)formation compared to single-phase La_(0.7)Ba_(0.3)MnO_(3-δ) or BaMnO_(3),providing potential benefits as a cathode for fuel cells.Subsequently,La_(0.7)Ba_(0.3)MnO_(3-δ)+BaMnO_(3) nanocomposites were utilized as the cathode for proton-conducting solid oxide fuel cells(H-SOFCs),which significantly improved cell performance.At 700 C,H-SOFC with a La_(0.7)Ba_(0.3)MnO_(3-δ)+BaMnO_(3) nanocomposite cathode achieved the highest power density(1504 mW·cm^(-2))yet recorded for H-SOFCs with manganate cathodes.This performance was much greater than that of single-phase La_(0.7)Ba_(0.3)MnO_(3-δ)or BaMnO_(3) cathode cells.In addition,the cell demonstrated excellent working stability.First-principles calculations indicated that the La_(0.7)Ba_(0.3)MnO_(3-δ)/BaMnO_(3) interface was crucial for the enhanced cathode performance.The oxygen reduction reaction(ORR)free energy barrier was significantly lower at the La_(0.7)Ba_(0.3)MnO_(3-δ)/BaMnO_(3) interface than that at the La_(0.7)Ba_(0.3)MnO_(3-δ) or BaMnO_(3) surfaces,which explained the origin of high performance and gave a guide for the construction of novel cathodes for H-SOFCs.展开更多
A new medium entropy material LiCo_(0.25)Fe_(0.25)Mn_(0.2)5Ni_(0.2)5O_(2)(LCFMN)is proposed as a cathode for proton-conducting solid oxide fuel cells(H-SOFCs).Unlike traditional LiXO_(2)(X=Co,Fe,Mn,Ni)lithiated oxides...A new medium entropy material LiCo_(0.25)Fe_(0.25)Mn_(0.2)5Ni_(0.2)5O_(2)(LCFMN)is proposed as a cathode for proton-conducting solid oxide fuel cells(H-SOFCs).Unlike traditional LiXO_(2)(X=Co,Fe,Mn,Ni)lithiated oxides,which have issues like phase impurity,poor chemical compatibility,or poor fuel cell performance,the new LCFMN material mitigates these problems,allowing for the successful preparation of pure phase LCFMN with good chemical and thermal compatibility to the electrolyte.Furthermore,the entropy engineering strategy is found to weaken the covalence bond between the metal and oxygen in the LCFMN lattice,favoring the creation of oxygen vacancies and increasing cathode activity.As a result,the H-SOFC with the LCFMN cathode achieves an unprecedented fuel cell output of 1803 mW·cm^(−2)at 700℃,the highest ever reported for H-SOFCs with lithiated oxide cathodes.In addition to high fuel cell performance,the LCFMN cathode permits stable fuel cell operation for more than 450 h without visible degradation,demonstrating that LCFMN is a suitable cathode choice for H-SOFCs that combining high performance and good stability.展开更多
The development of proton,oxygen-ion,and electron mixed conducting materials,known as triple-conduction materials,as cathodes for proton-conducting solid oxide fuel cells(H-SOFCs)is highly desired because they can inc...The development of proton,oxygen-ion,and electron mixed conducting materials,known as triple-conduction materials,as cathodes for proton-conducting solid oxide fuel cells(H-SOFCs)is highly desired because they can increase fuel cell performance by extending the reaction active area.Although oxygen-ion and electron conductions can be measured directly,proton conduction in these oxides is usually estimated indirectly.Because of the instability of cathode materials in a reducing environment,direct measurement of proton conduction in cathode oxide is difficult.The La0.8Sr0.2Sc0.5Fe0.5O3–δ(LSSF)cathode material is proposed for H-SOFCs in this study,which can survive in an H_(2)-containing atmosphere,allowing measurement of proton conduction in LSSF by hydrogen permeation technology.Furthermore,LSSF is discovered to be a unique proton and electron mixed-conductive material with limited oxygen diffusion capability that is specifically designed for H-SOFCs.The LSSF is an appealing cathode choice for H-SOFCs due to its outstanding CO_(2)tolerance and matched thermal expansion coefficient,producing a record-high performance of 2032 mW cm^(−2)at 700℃and good long-term stability under operational conditions.The current study reveals that a new type of proton–electron mixed conducting cathode can provide promising performance for H-SOFCs,opening the way for developing high-performance cathodes.展开更多
价格低廉且高效的电催化剂是加速燃料电池商业化的关键.本文采用一步水热法制备出直径约3.5 nm的超细PdPb纳米线.在钯基双金属纳米结构中引入铅后,不同组成的PdPb纳米线与钯纳米颗粒的形貌差异较大.XRD、TEM、XPS和电化学表征结果证实,...价格低廉且高效的电催化剂是加速燃料电池商业化的关键.本文采用一步水热法制备出直径约3.5 nm的超细PdPb纳米线.在钯基双金属纳米结构中引入铅后,不同组成的PdPb纳米线与钯纳米颗粒的形貌差异较大.XRD、TEM、XPS和电化学表征结果证实,由于双金属间的协同效应,PdPb纳米线的电催化活性和耐久性均优于钯纳米颗粒.其中,Pd65Pb35的乙醇电氧化电流密度最高,可达3460 mA mgPd^−1,约为商业Pd/C的6.3倍.HRTEM测试和经酸性介质长期处理后的表征结果显示,Pd65Pb35表面原子的优化排列和丰富的缺陷使其表现出高性能.此外,本文讨论和分析了不同铅含量的PdPb纳米线之间形貌和电催化活性的差异.展开更多
LiCoO_(2),a widely used electrode material for Li-ion batteries,was found to be suitable as a cathode material for proton-conducting solid oxide fuel cells(H-SOFCs).Although the evaporation of Li in LiCoO_(2) was detr...LiCoO_(2),a widely used electrode material for Li-ion batteries,was found to be suitable as a cathode material for proton-conducting solid oxide fuel cells(H-SOFCs).Although the evaporation of Li in LiCoO_(2) was detrimental to the Li-ion battery performance,the Li-evaporation was found to be beneficial for the H-SOFCs.The partial evaporation of Li in the LiCoO_(2) material preparation procedure led to the in-situ formation of the LiCoO_(2)+Co_(3)O_(4) composite.Compared to the cell using the pure phase LiCoO_(2) cathode that only generated moderate fuel cell performance,the H-SOFCs using the LiCoO_(2)+Co_(3)O_(4) cathode showed a high fuel cell performance of 1160 mW·cm^(-2) at 700℃,suggesting that the formation of Co_(3)O_(4) was critical for enhancing the performance of the LiCoO_(2) cathode.The first-principles calculation gave insights into the performance improvements,indicating that the in-situ formation of Co_(3)O_(4) due to the Li-evaporation in LiCoO_(2) could dramatically decrease the formation energy of oxygen vacancies that is essential for the high cathode performance.The evaporation of Li in LiCoO_(2),which is regarded as a drawback for the Li-ion batteries,is demonstrated to be advantageous for the H-SOFCs,offering new selections of cathode candidates for the H-SOFCs.展开更多
A nonmetal doping strategy was exploited for the conventional La_(0.5)Sr_(0.5)FeO_(3-δ)(LSF)cathode,allowing high performance for proton-conducting solid oxide fuel cells(H-SOFCs).Unlike previous studies focusing on ...A nonmetal doping strategy was exploited for the conventional La_(0.5)Sr_(0.5)FeO_(3-δ)(LSF)cathode,allowing high performance for proton-conducting solid oxide fuel cells(H-SOFCs).Unlike previous studies focusing on the utilization of metal oxides as dopants,phosphorus,which is a nonmetal element,was used as the cation dopant for LSF by partially replacing Fe ions to form the new La_(0.5)Sr_(0.5)Fe_(0.9)P_(0.1)O_(3-δ)(LSFP)compound.The H-SOFC using the LSFP cathode showed a two-fold peak power density as compared to that using the LSF cathode.Both experimental studies and first-principle calculations were used to unveil the mechanisms for the high performance of the LSFP cells.展开更多
基金the Financial support from the National key Research and Development Program of China(Nso.2018YFB0406502,2016YFB1102201)the National Natural Science Foundation of China(Grant No.51321091)+2 种基金the key Research and Development Program of Shandong Province(No.2018CXGC0410)the Young Scholars Program of Shandong University(No.2015WLJH36)the 111 Project 2.0(No.BP2018013)
文摘As a wide-bandgap semiconductor(WBG), β-Ga_2O_3 is expected to be applied to power electronics and solar blind UV photodetectors. In this review, defects in β-Ga_2O_3 single crystals were summarized, including dislocations, voids, twin, and small defects. Their effects on device performance were discussed. Dislocations and their surrounding regions can act as paths for the leakage current of SBD in single crystals. However, not all voids lead to leakage current. There's no strong evidence yet to show small defects affect the electrical properties. Doping impurity was definitely irrelated to the leakage current. Finally, the formation mechanism of the defects was analyzed. Most small defects were induced by mechanical damages. The screw dislocation originated from a subgrain boundary. The edge dislocation lying on a plane slightly tilted towards the(102) plane, the(101) being the possible slip plane. The voids defects like hollow nanopipes, PNPs, NSGs and line-shaped grooves may be caused by the condensation of excess oxygen vacancies, penetration of tiny bubbles or local meltback. The nucleation of twin lamellae occurred at the initial stage of "shoulder part" during the crystal growth. These results are helpful in controlling the occurrence of crystal defects and improving the device performance.
基金supported by the National Natural Science Foundation of China(51972183)the Hundred Youth Talents Program of Hunan,and the Startup Funding for Talents at the University of South China.
基金supported by the National Natural Science Foundation of China(Grant Nos.52272216 and 51972183)the Hundred Youth Talents Program of Hunan,and the Startup Funding for Talents at University of South China.
文摘A pure phase BaCo_(0.5)Fe_(0.5)O_(3–δ)(BCF),which cannot be obtained before,is successfully prepared in this study by using the calcination method with a rapid cooling procedure.The successful preparation of BCF allows the evaluation of this material as a cathode for proton-conducting solid oxide fuel cells(H-SOFCs)for the first time.An H-SOFC using the BCF cathode achieves an encouraging fuel cell performance of 2012 mW·cm–2 at 700,two℃-fold higher than that of a similar cell using the classical high-performance Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3–δ)(BSCF)cathode.First-principles calculations reveal the mechanism for the performance enhancement,indicating that the new BCF cathode significantly lowers the energy barriers in the oxygen reduction reaction(ORR)compared with the BSCF cathode.Therefore,improved cathode performance and fuel cell output are obtained for the BCF cell.The fuel cell using the BCF cathode also shows excellent long-term stability that can work stably for nearly 900 h without noticeable degradations.The fuel cell performance and long-term stability of the current BCF cell are superior to most of the H-SOFCs reported in previous reports,suggesting that BCF is a promising cathode for H-SOFCs.
基金supported by the National Natural Science Foundation of China(Grant Nos.52272216 and 51972183)the Hundred Youth Talents Program of Hunan,and the Startup Funding for Talents at University of South Chinathe support from the Hunan University Student Innovation and Entrepreneurship Training Program(Grant No.S202210555343)。
文摘A La_(0.5)Ba_(0.5)MnO_(3-δ) oxide was prepared using the sol-gel technique.Instead of a pure phase,La_(0.5)Ba_(0.5)MnO_(3-δ) was discovered to be a combination of La_(0.7)Ba_(0.3)MnO_(3-δ) and BaMnO_(3).The in-situ production of La_(0.7)Ba_(0.3)MnO_(3-δ)+BaMnO_(3) nanocomposites enhanced the oxygen vacancy(Vo)formation compared to single-phase La_(0.7)Ba_(0.3)MnO_(3-δ) or BaMnO_(3),providing potential benefits as a cathode for fuel cells.Subsequently,La_(0.7)Ba_(0.3)MnO_(3-δ)+BaMnO_(3) nanocomposites were utilized as the cathode for proton-conducting solid oxide fuel cells(H-SOFCs),which significantly improved cell performance.At 700 C,H-SOFC with a La_(0.7)Ba_(0.3)MnO_(3-δ)+BaMnO_(3) nanocomposite cathode achieved the highest power density(1504 mW·cm^(-2))yet recorded for H-SOFCs with manganate cathodes.This performance was much greater than that of single-phase La_(0.7)Ba_(0.3)MnO_(3-δ)or BaMnO_(3) cathode cells.In addition,the cell demonstrated excellent working stability.First-principles calculations indicated that the La_(0.7)Ba_(0.3)MnO_(3-δ)/BaMnO_(3) interface was crucial for the enhanced cathode performance.The oxygen reduction reaction(ORR)free energy barrier was significantly lower at the La_(0.7)Ba_(0.3)MnO_(3-δ)/BaMnO_(3) interface than that at the La_(0.7)Ba_(0.3)MnO_(3-δ) or BaMnO_(3) surfaces,which explained the origin of high performance and gave a guide for the construction of novel cathodes for H-SOFCs.
基金supported by the National Natural Science Foundation of China(Grant Nos.52272216 and 51972183)the Hundred Youth Talents Program of Hunan,and the Startup Funding for Talents at University of South China.
文摘A new medium entropy material LiCo_(0.25)Fe_(0.25)Mn_(0.2)5Ni_(0.2)5O_(2)(LCFMN)is proposed as a cathode for proton-conducting solid oxide fuel cells(H-SOFCs).Unlike traditional LiXO_(2)(X=Co,Fe,Mn,Ni)lithiated oxides,which have issues like phase impurity,poor chemical compatibility,or poor fuel cell performance,the new LCFMN material mitigates these problems,allowing for the successful preparation of pure phase LCFMN with good chemical and thermal compatibility to the electrolyte.Furthermore,the entropy engineering strategy is found to weaken the covalence bond between the metal and oxygen in the LCFMN lattice,favoring the creation of oxygen vacancies and increasing cathode activity.As a result,the H-SOFC with the LCFMN cathode achieves an unprecedented fuel cell output of 1803 mW·cm^(−2)at 700℃,the highest ever reported for H-SOFCs with lithiated oxide cathodes.In addition to high fuel cell performance,the LCFMN cathode permits stable fuel cell operation for more than 450 h without visible degradation,demonstrating that LCFMN is a suitable cathode choice for H-SOFCs that combining high performance and good stability.
基金National Natural Science Foundation of China,Grant/Award Numbers:52272216,51972183Hundred Youth Talents Program of HunanStartup Funding for Talents at University of South China。
文摘The development of proton,oxygen-ion,and electron mixed conducting materials,known as triple-conduction materials,as cathodes for proton-conducting solid oxide fuel cells(H-SOFCs)is highly desired because they can increase fuel cell performance by extending the reaction active area.Although oxygen-ion and electron conductions can be measured directly,proton conduction in these oxides is usually estimated indirectly.Because of the instability of cathode materials in a reducing environment,direct measurement of proton conduction in cathode oxide is difficult.The La0.8Sr0.2Sc0.5Fe0.5O3–δ(LSSF)cathode material is proposed for H-SOFCs in this study,which can survive in an H_(2)-containing atmosphere,allowing measurement of proton conduction in LSSF by hydrogen permeation technology.Furthermore,LSSF is discovered to be a unique proton and electron mixed-conductive material with limited oxygen diffusion capability that is specifically designed for H-SOFCs.The LSSF is an appealing cathode choice for H-SOFCs due to its outstanding CO_(2)tolerance and matched thermal expansion coefficient,producing a record-high performance of 2032 mW cm^(−2)at 700℃and good long-term stability under operational conditions.The current study reveals that a new type of proton–electron mixed conducting cathode can provide promising performance for H-SOFCs,opening the way for developing high-performance cathodes.
基金This work was financially supported by the National Natural Science Foundation of China(21773133)Taishan Scholars Advantageous and Distinctive Discipline Program for supporting the research team of energy storage materials of Shandong Province,China.
文摘价格低廉且高效的电催化剂是加速燃料电池商业化的关键.本文采用一步水热法制备出直径约3.5 nm的超细PdPb纳米线.在钯基双金属纳米结构中引入铅后,不同组成的PdPb纳米线与钯纳米颗粒的形貌差异较大.XRD、TEM、XPS和电化学表征结果证实,由于双金属间的协同效应,PdPb纳米线的电催化活性和耐久性均优于钯纳米颗粒.其中,Pd65Pb35的乙醇电氧化电流密度最高,可达3460 mA mgPd^−1,约为商业Pd/C的6.3倍.HRTEM测试和经酸性介质长期处理后的表征结果显示,Pd65Pb35表面原子的优化排列和丰富的缺陷使其表现出高性能.此外,本文讨论和分析了不同铅含量的PdPb纳米线之间形貌和电催化活性的差异.
基金supported by the National Natural Science Foundation of China(Grant No.51972183)the Hundred Youth Talents Program of Hunanthe Startup Funding for Talents at University of South China.
文摘LiCoO_(2),a widely used electrode material for Li-ion batteries,was found to be suitable as a cathode material for proton-conducting solid oxide fuel cells(H-SOFCs).Although the evaporation of Li in LiCoO_(2) was detrimental to the Li-ion battery performance,the Li-evaporation was found to be beneficial for the H-SOFCs.The partial evaporation of Li in the LiCoO_(2) material preparation procedure led to the in-situ formation of the LiCoO_(2)+Co_(3)O_(4) composite.Compared to the cell using the pure phase LiCoO_(2) cathode that only generated moderate fuel cell performance,the H-SOFCs using the LiCoO_(2)+Co_(3)O_(4) cathode showed a high fuel cell performance of 1160 mW·cm^(-2) at 700℃,suggesting that the formation of Co_(3)O_(4) was critical for enhancing the performance of the LiCoO_(2) cathode.The first-principles calculation gave insights into the performance improvements,indicating that the in-situ formation of Co_(3)O_(4) due to the Li-evaporation in LiCoO_(2) could dramatically decrease the formation energy of oxygen vacancies that is essential for the high cathode performance.The evaporation of Li in LiCoO_(2),which is regarded as a drawback for the Li-ion batteries,is demonstrated to be advantageous for the H-SOFCs,offering new selections of cathode candidates for the H-SOFCs.
基金the National Natural Science Foundation of China,Grant/Award Number:51972183the Hundred Youth Talents Program of Hunanthe Startup Funding for Talents at University of South China。
文摘A nonmetal doping strategy was exploited for the conventional La_(0.5)Sr_(0.5)FeO_(3-δ)(LSF)cathode,allowing high performance for proton-conducting solid oxide fuel cells(H-SOFCs).Unlike previous studies focusing on the utilization of metal oxides as dopants,phosphorus,which is a nonmetal element,was used as the cation dopant for LSF by partially replacing Fe ions to form the new La_(0.5)Sr_(0.5)Fe_(0.9)P_(0.1)O_(3-δ)(LSFP)compound.The H-SOFC using the LSFP cathode showed a two-fold peak power density as compared to that using the LSF cathode.Both experimental studies and first-principle calculations were used to unveil the mechanisms for the high performance of the LSFP cells.
