调控双钙钛矿中高熵组分促进高温析氧反应

固体氧化物电解池(SOEC)中阳极析氧反应动力学较为迟缓,限制了SOEC器件电催化转化能力,因此针对阳极材料的改性研究对于进一步提升SOEC电化学性能十分关键。高熵钙钛矿(HEP)在许多反应中表现出良好的催化活性,但在SOEC中的应用鲜有研究。本文通过在双钙钛矿的A位或A'位分别掺杂不同的稀土金属、碱土金属或碱金属离子,合成了(Pr_(0.2)La_(0.2)Sm_(0.2)Nd_(0.2)Gd_(0.2))BaCo_(2)O_(6-δ)(A-HEP)和Pr(Ba_(0.2)Sr_(0.2)Ca_(0.2)Na_(0.2)K_(0.2))Co_(2)O_(6-δ)(A'-HEP)两种高熵钙钛矿材料。由于掺杂离子平均半径和氧化态的差异,A-HEP保持四方双钙钛矿相结构而A'-HEP则转变为正交单钙钛矿相。物理化学表征结果表明,A-HEP中Co平均价态更高,Co 2p-O 1s杂化更强,从而增加了电子转移路径并降低了转移能垒。同时,A-HEP中表面氧空位浓度更高,可为阳极析氧反应提供更多的活性位点。因此,在具有A-HEP阳极的SOEC中,与氧输运、电子传输和表界面反应过程相关的阳极极化电阻显著降低,并在800℃下实现最高1.76 A·cm^(-2)的电流密度和200 h的稳定性。本工作为高熵钙钛矿材料在SOEC阳极中的应用提供了新的策略。

Infiltration of Ce0.8Gd0.2O1.9 nanoparticles on Sr2Fe1.5Mo0.5O6-δ cathode for CO2 electroreduction in solid oxide electrolysis cell

Solid oxide electrolysis cell(SOEC) can electrochemically convert CO2 to CO at the gas-solid interface with a high current density and Faradaic efficiency, which has attracted increasing attentions in recent years.Exploring efficient catalyst for electrochemical CO2 reduction reaction(CO2 RR) at the cathode is a grand challenge for the research and development of SOEC. Sr2Fe1.5Mo0.5O6-δ(SFM) is one kind of promising cathode materials for SOEC, but suffers from insufficient activity for CO2 RR. Herein, Gd0.2Ce0.8O1.9(GDC)nanoparticles were infiltrated onto the SFM surface to construct a composite GDC-SFM cathode and improve the CO2 RR performance in SOEC. The current density over the GDC infiltrated SFM cathode with a GDC loading of 12.8 wt% reaches 0.446 A cm-2 at 1.6 V and 800 °C, which is much higher than that over the SFM cathode(0.283 A cm-2). Temperature-programmed desorption of CO2 measurements suggest that the infiltration of GDC nanoparticles significantly increases the density of surface active sites and three phase boundaries(TPBs), which are beneficial for CO2 adsorption and subsequent conversion. Electrochemical impedance spectroscopy results indicate that the polarization resistance of 12.8 wt% GDCSFM cathode was obviously decreased from 0.46 to 0.30 cm^2 after the infiltration of GDC nanoparticles.

Improving the performance of solid oxide electrolysis cell with gold nanoparticles-modified LSM-YSZ anode

Gold, as the common current collector in solid oxide electrolysis cell(SOEC), is traditionally considered to be inert for oxygen evolution reaction at the anode of SOEC. Herein, gold nanoparticles were loaded onto conventional strontium doped lanthanum manganite-yttria stabilized zirconia(LSM-YSZ) anode, which evidently improved the performance of oxygen evolution reaction at 800 °C. The current densities at 1.2 V and 1.4 V increased by 60.0% and 46.9%, respectively, after loading gold nanoparticles onto the LSM-YSZ anode. Physicochemical characterizations and electrochemical measurements suggested that the improved SOEC performance was attributed to the accelerated electron transfer of elementary process in anodic polarization reaction and the newly generated triple phase boundaries in gold nanoparticles-loaded LSMYSZ anode.

Co-electrolysis of CO_2 and H_2O in high-temperature solid oxide electrolysis cells: Recent advance in cathodes

Co-electrolysis of CO2and H2O using high-temperature solid oxide electrolysis cells(SOECs) into valuable chemicals has attracted great attentions recently due to the high conversion and energy efficiency,which provides opportunities of reducing CO2emission, mitigating global warming and storing intermittent renewable energies. A single SOEC typically consists of an ion conducting electrolyte, an anode and a cathode where the co-electrolysis reaction takes place. The high operating temperature and difficult activated carbon-oxygen double-bond of CO2put forward strict requirements for SOEC cathode. Great efforts are being devoted to develop suitable cathode materials with high catalytic activity and excellent long-term stability for CO2/H2O electro-reduction. The so far cathode material development is the key point of this review and alternative strategies of high-performance cathode material preparation is proposed. Understanding the mechanism of CO2/H2O electro-reduction is beneficial to highly active cathode design and optimization. Thus the possible reaction mechanism is also discussed. Especially, a method in combination with electrochemical impedance spectroscopy(EIS) measurement, distribution functions of relaxation times(DRT) calculation, complex nonlinear least square(CNLS) fitting and operando ambient pressure X-ray photoelectron spectroscopy(APXPS) characterization is introduced to correctly disclose the reaction mechanism of CO2/H2O co-electrolysis. Finally, different reaction modes of the CO2/H2O coelectrolysis in SOECs are summarized to offer new strategies to enhance the CO2conversion. Otherwise,developing SOECs operating at 300-600 °C can integrate the electrochemical reduction and the Fischer-Tropsch reaction to convert the CO2/H2O into more valuable chemicals, which will be a new research direction in the future.

Highly dispersed nickel species on iron‐based perovskite for CO_(2) electrolysis in solid oxide electrolysis cell

Feasible construction of cathode materials with highly dispersed active sites can extend the tri‐ple‐phase boundaries,and therefore leading to enhanced electrode kinetics for CO_(2) electrolysis in solid oxide electrolysis cell(SOEC).Herein,highly dispersed nickel species with low loading(1.0 wt%)were trapped within the La_(0.8)Sr_(0.2)FeO_(3)–δ‐Ce_(0.8)Sm_(0.2)O_(2)–δvia a facial mechanical milling ap‐proach,which demonstrated excellent CO_(2) electrolysis performance.The highly dispersed nickel species can significantly alter the electronic structures of the LSF‐SDC without affecting its porous network and facilitate oxygen vacancy formation,thus greatly promote the CO_(2) electrolysis perfor‐mance.The highest current density of 1.53 A·cm^(-2) could be achieved when operated under 800℃ at 1.6 V,which is about 91%higher than the LSF‐SDC counterpart.

Orthorhombic Y_(0.95-x)Sr_(x)Co_(0.3)Fe_(0.7)O_(3-δ) anode for oxygen evolution reaction in solid oxide electrolysis cells

Cubic perovskite oxides usually suffer from delamination and Sr^(2+) segregation for catalyzing oxygen evolution reaction (OER) at the anodes of solid oxide electrolysis cells (SOECs). It is crucial to develop alternative and efficient anode materials for SOECs. Herein, a series of novel Y_(0.95-x)Sr_(x)Co_(0.3)Fe_(0.7)O_(3-δ) (YSCF-x) orthorhombic perovskite oxides in the Pnma (62) space group are synthesized as anode materials of SOECs. Physicochemical characterizations and density functional theory calculations reveal that the partial substitution of Y^(3+) by Sr^(2+) increases the oxygen vacancy concentration and mobility as well as improves the electrical conductivity, which contributes to the excellent OER activity of YSCF-x. At 800 °C, the current density of SOEC with YSCF-0.05-Ce0.8Sm0.2O2-δ anode can reach 1.32 A cm^(−2) at 1.6 V, about twice that of SOEC with Y_(0.95-x)Sr_(x)Co_(0.3)Fe_(0.7)O_(3-δ)-Ce_(0.8)Sm_(0.2)O_(2-δ) anode. This work paves a new avenue for the design of advanced anode materials of SOECs.

In-situ exsolution of cobalt nanoparticles from La_(0.5)Sr_(0.5)Fe_(0.8)Co_(0.2)O_(3-δ) cathode for enhanced CO_(2) electrolysis performance

Solid oxide electrolysis cell(SOEC)is a promising technology for CO_(2) conversion and renewable energy storage with high efficiency.It is highly desirable to develop catalytically active cathodes for CO_(2) electrolysis.Herein,cathode materials with different structural stabilities are designed by Nb substitution on La_(0.5)Sr_(0.5)Fe_(0.8)Co_(0.2)O_(3-δ)(LSFC82)to obtain La_(0.5)Sr_(0.5)Fe_(0.7)Co_(0.2)Nb_(0.1)O_(3-δ)(LSFCN721)and La_(0.5)Sr_(0.5)Fe_(0.8)Co_(0.1)Nb_(0.1)O_(3-δ)(LSFCN811),respectively.LSFC82-Sm_(0.2)Ce_(0.8)O_(2-δ)(SDC)cathode with inferior structural stability(ability to maintain the structure)shows desirable CO_(2) electrolysis performance with the generated current density of 1.80 A cm^(-2)2 at 1.6 V and stable performance during 110 h operation at 1.2 V and 800℃.However,LSFC82 particles are collapsed into pieces after stability test with the generation of Co nanoparticles simultaneously.The frameworks of LSFCN721 and LSFCN811 particles maintain well because of the high-valent niobium,but Co exsolution,ox-ygen vacancy content and the corresponding CO_(2) electrolysis performance are restricted.This work confirms that Co nanoparticles can be exsolved from LSFC82-SDC cathode during CO_(2) electrolysis,providing references for constructing metallic nanoparticles decorated-perovskite cathodes for SOECs.