阳极电沉积Co-Ni混合氧化物在碱性介质中的电催化析氧性能

 利用电化学阳极共沉积技术,从含不同Co2+/Ni2+比的NaOH溶液中,在Ni基体上制备了Co-Ni混合氧化物. 利用X射线衍射分析了混合氧化物的物相结构,并通过循环伏安法、稳态Tafel曲线和电化学阻抗谱研究了混合氧化物作为析氧阳极材料的电催化活性. 结果表明,从n(Co2+)/n(Ni2+)=1的电解液中沉积所得的Co-Ni混合氧化物主要为尖晶石结构NiCo2O4相,并具有最高的析氧催化活性. 析氧反应在Co-Ni混合氧化物电极上表现出两个明显的Tafel区域: 在低电势区Tafel曲线斜率为40~48 mV/(°),对OH-的反应级数为2.0; 在高电势区Tafel曲线斜率为110~120 mV/(°),对OH-的反应级数为1.0. 在恒定电势E=0.60 V时,Co-Ni混合氧化物上析氧反应的电化学标准活化焓为37.4~51.7 kJ/mol. 通过对析氧历程的分析,提出了在不同电势范围内Co-Ni混合氧化物上析氧反应的动力学方程,并较好地解释了实验结果.     

丙酮酸在悬汞电极上的电化学行为及其与AI（Ⅲ）的相互作用

研究了酸性、中性、碱性范嗣内丙酮酸在悬汞电极上的电化学行为．对实验条件进行了优化．在最佳条件下丙酮酸的还原峰电流和浓度有良好的线性关系。同时在不同pH值条件下研究了AI（Ⅲ）和丙酮酸的相互作用，结果表明，不同pH值范围内AI（Ⅲ）和丙酮酸的相互作用均为弱作用，弱作用强度为酸性〉碱性〉中性。这种作用强度的差别可能来自于不同条件下AI（Ⅲ）的存在形态不同．     

聚苯胺衍生Fe-N-C催化剂在碱性电解质中对氧还原反应的催化性能

经过热解聚苯胺、碳和FeCl₃的混合物制备的Fe-N-C材料在酸性电解质中对氧还原反应表现出高的催化活性;由于材料中不存在任何贵金属, 因而被认为是一类新型非贵金属氧还原催化剂. 然而这类催化剂在碱性电解质中催化氧还原反应的性能如何尚不清楚. 本文使用旋转圆盘电极技术考察了制备的两个Fe-N-C催化剂在KOH水溶液中催化氧还原反应性能, 发现这两个催化剂表现出比无金属的N掺杂碳材料更高的活性. 与商业Pt/C催化剂相比, 它们催化氧还原反应的起始电势和半波电势分别仅低60和40 mV左右, 计时电流测试表明, 它们比Pt/C催化剂显示出更好的稳定性. 此外, 在这两个Fe-N-C催化剂上的氧还原反应主要遵循四电子途径. 本工作显示, Fe-N-C材料有望用于碱性燃料电池氧还原反应催化剂.     

玻碳电极上DTAB对氧还原反应的促进作用

用旋转圆盘玻碳电极研究了阳离子表面活性剂十二烷基三甲基溴化铵(DTAB)对氧还原反应的影响. 结果表明, DTAB明显提高了玻碳电极对氧还原的电催化活性. 通过对氧还原电流与旋转速度的关系以及动力学电流与电位的Tafel关系分析, 发现DTAB提高了玻碳电极对氧还原反应电荷传递步骤的传递系数, 因此加快了氧还原的动力学过程.     

L-半胱氨酸/漆酶修饰的纳米金阴极对氧还原的电催化

以四氯金酸和L-半胱氨酸为原料,合成了L-半胱氨酸功能化纳米金粒子,将此纳米粒子修饰在金盘电极表面并共价偶联漆酶分子。 以循环伏安法研究了此固定漆酶电极在无氧磷酸盐缓冲液中电化学行为和催化氧还原能力,并进一步评估了其作为氧传感器使用的性能：以计时电流法测定其对氧气的检测限,与氧气的亲和力（以米氏常数表征）,研究了传感器的长期使用性、热稳定性和pH-催化电流关系。 结果表明,此固定漆酶电极可以实现漆酶活性中心T2与导电纳米粒子间的直接电子迁移而无需任何外加电子中介体（氧化还原峰的式电位为192.5 mV vs AgCl/Ag）,并在接近漆酶活性中心T3氧化还原式电位（780 mV vs NHE）附近发生氧还原;测得的固酶电极与氧气的亲和力较高（米氏常数为216.4 μmol/L）且检测限低达0.22 μmol/L,在4 ℃下保存60 d后活力仍然保持初始活力的大约78%。 但这种电极的热稳定性较差,受pH值影响较明显,在pH值近于生理条件时几乎完全丧失活力。     

脊椎状NiCo2O4纳米棒的制备及其析氧和氧还原性能研究

以水热法并进一步焙烧合成脊椎状NiCo₂O₄纳米棒,通过透射电子显微镜（TEM）、X射线衍射仪（XRD）、X射线光电子能谱仪（XPS）和热重分析仪（TG）等来表征其结构形态及热稳定性.采用线性扫描法（LSV）、循环伏安（CV）研究所制备催化剂的在玻碳和旋转圆盘电极上的电催化活性：在0.1 mol·L^-1 KOH溶液中的电催化析氧反应（OER）和电催化氧还原反应（ORR）.研究结果表明,所制备的脊椎状NiCo₂O₄纳米棒有大量的不饱和态,200℃焙烧制备的脊椎状NiCo₂O₄纳米棒析氧过电位最小可达309 mV,Tafel斜率145.6 mV/dec,其氧还原极限电流密度在1600 rmp可达到5.095 mA·cm^-2,电子转移数在3.2~3.8之间,接近四电子转移机理,其优良电化学性能可能是由于暴露了更多的边缘缺陷的缘故.     

丙酮酸在悬汞电极上的电化学行为及其与Al髥的相互作用

研究了酸性、中性、碱性范围内丙酮酸在悬汞电极上的电化学行为,对实验条件进行了优化,在最佳条件下丙酮酸的还原峰电流和浓度有良好的线性关系。同时在不同pH值条件下研究了Al髥和丙酮酸的相互作用,结果表明,不同pH值范围内Al髥和丙酮酸的相互作用均为弱作用,弱作用强度为酸性>碱性>中性。这种作用强度的差别可能来自于不同条件下Al髥的存在形态不同。     

CoPy/C催化剂应用碱性介质氧还原催化的电化学性能

利用碳黑（Vulcan XC-72R）中加入硫酸钴和吡啶（Py）作为催化剂前驱体,经溶剂分散热处理构建了一类新型的高效氧还原CoPy/C复合催化剂.并运用循环伏安法（CV）和旋转圆盘电极（RDE）技术研究了不同Co含量的CoPy/C催化剂在碱性介质中对氧还原的电催化活性.结果表明:Co的存在对氧的催化剂活性位的形成有重要影响,800℃下所制备的10%Co30%Py/C（质量分数）复合催化剂表现出最佳的氧还原催化活性.以其制备的气体扩散电极在3.0 mol·L^-1KOH电解质溶液（O₂气氛）中0.014 V（相对于标准氧电极（RHE））即可产生明显的氧还原电流.同40%Py/C相比,10%Co30%Py/C催化氧还原的起峰电位正移了71 mV,同时表现出明显的极限扩散电流.在-0.16 V时电流密度达到最大值,电流密度为1.0 mA·cm^-2,半波电位在-0.07 V.透射电镜分析表明所制备的碳黑载吡啶钴（10%Co30%Py/C）催化剂平均粒径为20 nm.     

丙酮酸在悬汞电极上的电化学行为及其与Al(Ⅲ)的相互作用

研究了酸性、中性、碱性范围内丙酮酸在悬汞电极上的电化学行为，对实验条件进行了优化，在最佳条件下丙酮酸的还原峰电流和浓度有良好的线性关系。同时在不同pH值条件下研究了Al(Ⅲ)和丙酮酸的相互作用，结果表明，不同pH值范围内Al(Ⅲ)和丙酮酸的相互作用均为弱作用，弱作用强度为酸性>碱性>中性。这种作用强度的差别可能来自于不同条件下Al(Ⅲ)的存在形态不同。     

不同结构及氮掺杂NiO/rGO氧还原催化剂的制备与性能研究

本文以还原氧化石墨烯（rGO）为载体制备了片状NiO/rGO和球形NiO/N-rGO结构的氧还原催化剂. 通过X-射线衍射（XRD）、Raman（拉曼）测试、X-射线光电子能谱（XPS）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）等方法表征了两种催化剂的结构和形貌. 采用循环伏安法（CV）、Tafel曲线、线性扫描伏安法（LSV）、旋转圆盘电极（RDE）和旋转环盘电极（RRDE）等技术测试研究了两种催化剂的电化学催化氧还原性能. 研究结果表明,球形NiO/N-rGO催化剂催化氧还原的峰电流密度和起始电位（0.89 V vs. RHE）与商业化的Pt/C（20%）催化剂相近. 旋转圆盘电极（RDE）和旋转环盘电极（RRDE）测试证明,在碱性电解液中NiO/rGO和NiO/N-rGO催化的氧还原反应均主要通过4?鄄电子途径反应途径发生,球形NiO/N-rGO催化剂展现出替代Pt/C基催化剂的潜力.     

The oxygen evolution reaction on cobalt: Part II. Transient measurements

Open-circuit overpotential decays on an aged cobalt electrode in the oxygen evolution range in 6 M KOH show different slopes for two overpotential regions. These slopes are lower than the Tafel slope in the same region: Tafel slopes of ～100 and ～40 mV/dec, at high and low overpotentials, respectively. compared to decay slopes of ～?60 and ～?20 to ?30 mV/dec. For a fresh cobalt electrode a decay slope of ～?40 mV/dec is found at high overpotentials. From impedance measurements during a decay it is concluded that the electrode capacitance cannot account for the decay curves obsered. By means of steady-state potentiostatic impedance measurements (with stabilization times > 24 h) it is found that the differential Tafel slope remains constant at ～40–50 mV/dec and differs considerably from the Tafel slope at high overpotentials, ～100 mV/dec. Galvanostatic pulse experiments give evidence of the presence of CoO₂ in the oxide layer.Two models which may explain the observed experimental results are analysed. Both include a potential-dependent (extra) process which is fixed by the amount of CoO₂ at the surface. In one model, CoO₂ is responsible for partial surface blockage (parallel process); in the other model, CoO₂ controls the conductivity of the top layer of the oxide layer on the electrode.     

无电沉积硼化镍材料对水氧化的电催化性能

通过无电沉积/化学镀的方法分别制得石墨烯(Graphene)、 镍网(Ni foam, NF)、 钛网(Ti mesh, TM)、 碳布(Carbon cloth, CC)负载的硼化镍材料. 其中在石墨烯基底上生长的硼化镍层由规则的纳米颗粒构成, 且均匀致密. 对几种材料在碱性条件下(1.0 mol/L KOH电解质中)的水氧化电催化性能进行了研究, 结果表明, 石墨烯基底上生长的硼化镍材料(NiB_x/graphene)具有最佳的水氧化电催化性能. 电流密度达到10 mA/cm²时的过电位仅为277 mV, 相应的Tafel斜率为57 mV/dec. 对石墨烯负载的硼化镍材料进行烧结, 测得过电位为330 mV, 与未烧结的样品相比电催化活性下降. 该方法所制的石墨烯负载的硼化镍材料兼具高电催化活性和稳定性, 为低成本、 高效率的水氧化非贵金属电催化剂的制备提供了新思路.     

Impedance measurements in different alkaline solutions on an oxygen-evolving La0.5Sr0.5CoO3 electrode

It was found that the oxygen evolution reaction on La_0.5Sr_0.5CoO₃ in strong alkaline solutions has a Tafel slope of ～ 60 mV/dec and a reaction order at constant overpotential with respect to the KOH activity of 0.6–0.8. From impedance measurements differential Tafel slopes were calculated and were found to be ～ 60 mV/dec at overpontentials > 250 mV. Effective capacitances having a broad maximum at an overpotential of about 200 mV in all alkaline solutions were calculated. The effective capacitance increased with increasing KOH concentration. Furthermore, the material decomposed at the surface when exposed to strong oxygen evolution. From the results a modified Krasil'shchikov reaction path is analysed.     

The Direct Electron Transfer of Iron‐containing Metal Organic Frameworks (Mil‐100) and Its Catalysis for the Oxygen Reduction Reaction in Room‐Temperature Alkaline Media on a Glass Carbon Electrode

The most common electrocatalysts for the oxygen reduction reaction (ORR) are platinum‐based ones. This work demonstrates the performance of iron‐containing metal organic frameworks (MOFs) as non‐platinum‐based nano‐electrocatalysts for ORR in an alkaline medium. As a new non‐platinum catalyst to achieve the active sites for the ORR, Mil‐100 (Fe) nanoparticles were used in aqueous KOH by the rotating‐disk electrode method. The main objectives of this study are the investigations on the electron transfer number (n ), Tafel slope, and catalytic performance. The particles size of the obtained powders is in the nanoscale range (approximately 25 nm). The electron transfer number for the ORR on the surface of iron‐containing catalyst is approximately 4, and the Tafel slope of diffusion‐corrected kinetic current density is ~50.7 mV per decade at low overpotential. This work might extend a new non‐precious‐metal catalyst structure for ORR for use in low‐temperature fuel cells.     

Highly efficient Fe_xNi_(1-x)O_y/CP electrode prepared via simple soaking and heating treatments for electrocatalytic water oxidation

The oxygen evolution reaction(OER) is a key step in the overall water splitting process. Numerous electrocatalysts have been developed to lower the overpotential and accelerate the kinetics of the OER. In this work, a simple soaking and heating treatment was used to form a stable and efficient Fe_xNi_(1-x)O_y/CP electrode. The electrode combined nickel and iron oxides on a commercial carbon paper were used for electrocatalytic water oxidation. The best Fe_xNi_(1-x)O_y/CP electrode(Ni/Fe = 15/1) displayed a current density of 10 mA/cm~2 at a low overpotential of 290 mV in 0.1 M KOH solution with a Tafel slope of 52 mV/dec.A higher current density of ~50 mA/cm~2 at the same overpotential and a lower Tafel slope of 43 mV/dec was obtained for this electrode in 1.0 M KOH solution. Excellent durability of the Fe_xNi_(1-x)O_y/CP electrode in 1.0 M KOH solution was confirmed under a high current density of 136 mA/cm~2 at an overpotential of 340 mV.     

氧化石墨烯基钴卟啉复合材料的电催化析氢反应

制备了5,10,15,20-四(苯基)卟啉钴配合物(CoTPP), 并利用该配合物与氧化石墨烯(GO)的π?π堆积作用组装了CoTPP/GO电催化产氢复合材料. 研究发现, 当CoTPP与GO的质量比为1∶15时, 复合材料的性能最佳. 该材料的拉曼和扫描电子显微镜结果显示, 与GO相比, CoTPP/GO复合材料表面的无序程度增加, 形貌改变有利于促进反应体系的电荷迁移与分离; 交流阻抗测试结果显示, 阻抗值由GO的1180 Ω降低为CoTPP/GO材料的734 Ω; 电化学测试结果显示, 析氢起始过电位由-761 mV降低为-337 mV, 塔菲尔斜率由296 mV/dec 降低至174 mV/dec, 法拉第效率却由23%提高至87%. 加入二苯硫醚(SPh₂)轴向配体后, CoTPP(SPh₂)/GO材料的析氢起始过电位进一步降低至-235 mV, 塔菲尔斜率降低至163 mV/dec, 法拉第效率提高至94%. 研究结果表明, 通过氧化石墨烯与金属卟啉的非共价键自组装是构筑石墨烯基电催化产氢材料的一个有效途径.     

Temperature Effect on Hydrogen Evolution Reaction at Au Electrode

The temperature dependence of hydrogen evolution reaction (HER) at a quasi-single crys-talline gold electrode in both 0.1 mol/L HClO₄ and 0.1 mol/L KOH solutions was investigated by cyclic voltammetry. HER current displays a clear increase with reaction overpotential (η) and temperature from 278～333 K. In 0.1 mol/L HClO₄ the Tafel slopes are found to increases slightly with temperature from 118 mV/dec to 146 mV/dec, while in 0.1 mol/L KOH it is ca. 153±15 mV/dec without clear temperature-dependent trend. The apparent activation energy (Ea) for HER at equilibrium potential is ca. 48 and 34 kJ/mol in 0.1 mol/L HClO₄ and 0.1 mol/L KOH, respectively. In acid solution, Ea decreases with increase in η, from Ea=37 kJ/mol (η=0.2 V) to 30 kJ/mol (η=0.35 V). In contrast, in 0.1 mol/L KOH, Ea does not show obvious change with η. The pre-exponential factor (A) in 0.1 mol/L HClO₄ is ca. 1 order higher than that in 0.1 mol/L KOH. Toward more negative potential, in 0.1 mol/L HClO₄ A changes little with potential, while in 0.1 mol/L KOH it displays a monotonic increase with η. The change trends of the potential-dependent kinetic parameters for HER at Au electrode in 0.1 mol/L HClO₄ and that in 0.1 mol/L KOH are discussed.     

Atomically Dispersed Pt on Screw-like Pd/Au Core-shell Nanowires for Enhanced Electrocatalysis

Engineering noble metal nanostructures at the atomic level can significantly optimize their electrocatalytic performance and remarkably reduce their usage. We report the synthesis of atomically dispersed Pt on screw-like Pd/Au nanowires by using ultrafine Pd nanowires as seeds. Au can selectively grow on the surface of Pd nanowires by an island growth pattern to fabricate surface defect sites to load atomically dispersed Pt, which can be confirmed by X-ray absorption fine structure measurements and aberration corrected HRTEM images. The nanowires with 2.74 at % Pt exhibit superior HER properties in acidic solution with an overpotential of 20.6 mV at 10 mA cm⁻² and enhanced alkaline ORR performance with a mass activity over 15 times greater than the commercial platinum/carbon (Pt/C) catalysts.     

Pt（111）电极上O2与OHad的吸脱附及氧还原反应动力学

研究了Pt（111）电极在0．1mol／LHClO4溶液中O2吸附与OHad脱附及氧还原反应的动力学．研究发现OHad的可逆吸脱附速率很快;在氧还原的动力学或动力学与传质混合控制区,恒电位下氧还原的电流随反应时间缓慢衰减,在转速较大,扫速较慢的情形下正向扫描过程中氧还原的电流总是明显低于逆向扫描的电流;Pt／0．1mol／LHClO4从无O2切换到O2饱和时,其开路电位迅速从0．9V增加到1．0V．结果表明,Pt（111）电极上O2解离生成OHad速率很快,ORR过程中OHad会在表面缓慢积累,氧还原反应的动力学主要由反应 OHad＋H^＋＋e→←H2O的平衡热力学决定．     

非晶态NiP基催化剂的制备及电催化析氢性能研究

以NaH₂PO₂和Ni₂SO₄为磷源和镍源,使用一锅法合成了非晶态NiP合金及其碳纳米（乙炔黑和石墨烯）复合催化剂。用透射电子显微镜（TEM）、X射线衍射仪（XRD）、热重分析（TGA）、电感耦合等离子体光谱仪（ICP）分别对催化剂性能和组成进行了表征和分析。通过线性扫描伏安对催化剂在酸性和碱性条件下的析氢性能进行了评价,研究结果表明,非晶态NiP/还原氧化石墨烯复合催化剂（NiP/RGO）展现出优异的电催化性能。在0.5 mol/L H₂SO₄中的起始过电位为89.0 mV,塔菲尔斜率为135.1 mV/decade;在1 mol/L NaOH中,起始过电位为116.1 mV,塔菲尔斜率为122.4 mV/decade,这与商业化Pt黑催化剂很接近。500次循环以后,催化剂活性没有明显下降,表明该催化剂具有良好的稳定性。该研究提供了一种简单可行的制备非贵金属磷化物方法用于电催化析氢反应。