非晶Nd-Ni-B/NF稀土复合电极材料的制备及其析氢性能

本研究采用简单的一步化学沉积法制备非晶纳米Nd-Ni-B/NF稀土复合电极并研究其析氢(Hydrogen evolution reaction, HER)性能。通过各种测试方法对纳米电极材料进行物相分析和形貌表征,并探索其电催化析氢性能和稳定性。结果表明, 稀土Nd可提高电极的电催化析氢性能, 当硝酸钕浓度为3 g?L^-1时, 恒温35 ℃下施镀1 h, 制备的Nd-Ni-B/NF电极析氢性能最佳。Nd-Ni-B/NF(Nickel foam)电极在1.0 mol?L^-1KOH 溶液中, 20 mA?cm^-2电流密度下的析氢过电位仅为180 mV, Tafel斜率为117 mV?dec^-1, 析氢反应由Volmer-Heyrovsky步骤控制。此外, Nd-Ni-B/NF电极具有优越的电化学稳定性, 在持续电解12 h或2000次循环伏安测试后, 催化剂的活性没有明显衰减。     

纳米晶碳化钨薄膜的析氢催化性能

采用等离子体增强化学气相沉积法制备了具有纳米结构的碳化钨薄膜, 采用XRD、EDS、SEM方法表征了薄膜的表面形貌、化学组成和物相结构. 这种碳化钨纳米晶薄膜具有巨大的电化学比表面积、很好的电催化活性和电化学稳定性. 通过测试和计算表明, 几何面积为1cm²碳化钨薄膜/泡沫镍电极、碳化钨薄膜/镍电极的电化学比表面积分别为83.21和64.13cm2; 该薄膜电极材料的a值为0.422～0.452V, 接近低超电势材料; 析氢交换电流密度为4.02～4.22×10^-4A/cm²; 当超电势为263mV时, 其析氢反应的活化能为45.62～45.77kJ/mol.     

碱液中镍电极的析氢机理

研究镍电极在碱液中的析氢机理对开发二次清洁能源有指导意义,过去对其研究不够.通过Tafel曲线和电化学阻抗谱对镍电极在KOH溶液中的析氢机理进行了研究.结果表明,过电位低于600 mV时,析氢服从复合脱附机理,反应历程为电化学步骤+复合脱附步骤;过电位高于600 mV时,析氢服从迟缓放电机理或电化学脱附机理,反应历程为电化学步骤+电化学脱附步骤.     

Co3S4电极材料的制备及在碱性析氢反应中的重构行为研究

因为析氢反应(HER)电位远低于析氧反应(OER),催化剂的重构过程相对迟缓,所以其重构现象鲜有报道。为此,本工作通过水热和硫化两步法成功合成了自支撑碳布(CC)负载纯相Co₃S₄电极材料,其微观呈纳米颗粒组装的绿疣海葵状结构。该电极材料在1 mol/L KOH的HER电化学测试中就能发生快速、完全重构,催化活性显著提升,在100 mA·cm^-2时过电位降低约55 mV。诱发重构主要是硫组分浸出所致。重构后的电极材料物相为Co(OH)₂,且形貌已完全转变为数层纳米片堆叠而成的大比表面花状结构,暴露出更多的活性位点,促进电解液与电极材料的接触,加速催化反应中的传质过程,进而提升催化活性。这一发现有助于科研工作者初步认识硫化物催化剂电极材料在HER催化过程中的重构行为。     

硅电极表面镍钨磷合金电沉积及其析氢性能

Ni-W-P合金薄膜具有优良的催化析氢性能和耐蚀性.通过在半导体p型Si上恒电流沉积Ni-W-P合金薄膜,制备出Ni-W-P合金修饰的半导体p型Si电极.用SEM和XRD对合金薄膜的表面形貌、组成和结构进行了表征,以电极的阴极极化曲线对其催化析氢和光电催化析氢性能进行评价.结果表明:W,P质量分数分别为26.71%和0.95%的纳米晶合金修饰的p型Si电极具有优良的催化析氢性能和显著的光电析氢活性.     

Ni-W-TiO2复合镀工艺及其镀层性能研究

为了进一步提高Ni-W合金镀层的析氢电催化活性,用电沉积方法制备了Ni-W-TiO2复合镀层,通过阴极极化曲线和交流阻抗等电化学技术研究了其在碱性溶液中的析氢电催化活性,并用扫描电镜观察了电极的表面形貌.结果表明,在Ni-W合金中掺入TiO2微粒可增大电极的比表面积,并改变Ni-W合金在碱性介质中的析氢反应机理.Ni-W-TiO2复合镀层有较高的析氢电催化活性,可用作电解水反应的活性电极.     

富缺陷晶态WSe_2纳米片:一种潜在的高效低成本析氢反应电催化剂（英文）

氢是高效的清洁能源,在应对全球能源危机和环境污染方面具有重要作用。电解水制氢是通过消耗可再生的电能(水电、光电、风电等)和储量丰富的水资源以获得氢气,该方法制氢颇具应用前景。然而,电解水过程中的析氢反应(HER)动力学迟缓、过电位高,导致制氢能耗较大。为提升析氢反应速率,需在电解水设备中引入贵金属作为催化剂,这进一步增加了制氢成本。开发高效低成本的析氢催化剂对电解水制氢的规模化应用至关重要。过渡金属硫属化合物(TMDs)因具有独特的层状结构和较低的氢原子吸附自由能,表现出良好的析氢催化活性,有望成为贵金属催化剂的替代品。近年来,MoS_2、WS_2、TiS_2、TaS_2、MoSe_2、WSe_2等TMDs材料被广泛用于催化析氢反应。TMDs的边缘位点被认为是其催化活性中心,且材料的催化性能与边缘位点数成正比。研究表明,通过缺陷调控增加边缘位点数是提升TMDs催化活性的不二法门。液相加工及其他低温合成法是目前制备富缺陷TMDs析氢催化剂的有效手段,然而该条件下得到的材料结晶性差、易发生电化学腐蚀、析氢稳定性低。高温处理可合成高结晶性的TMDs,具有较好的电化学稳定性。但高温结晶会使材料比表面积减小、缺陷和边缘位点数减少,造成催化活性不佳。采用化学/电化学剥离晶态TMDs样品,可在室温条件下制备富缺陷晶态TMDs析氢催化剂。然而,此方法受限于易燃溶剂的使用,且制备过程繁琐,难以实现规模化生产。因此,富缺陷晶态TMDs的制备,是高效析氢催化剂领域的研究重点和难点。在已报道的TMDs中,WSe_2因带隙小(1.6 eV)、导电性好而备受关注,引发了微纳WSe_2催化剂的研究热潮。其中,片状WSe_2有利于材料活性位点与电解液直接接触,通常表现出更优异的析氢催化活性。类似其他TMDs材料,富缺陷晶态WSe_2纳米片的制备,目前仍难以实现。本工作以WO_3和Se粉为原料,先在高温条件下合成高结晶度WSe_2,再经超声剥离得到晶态的WSe_2纳米片。在随后的长时间超声作用下,晶态WSe_2纳米片表面会进一步产生许多纳米级的岛状颗粒,得到富缺陷晶态WSe_2纳米片材料。选区衍射分析表明,岛状颗粒的引入使WSe_2纳米片新增了多晶衍射环。同时,材料的BET比表面积高达105.2 m~2·g~(-1),且具有更宽的孔径分布和更大的孔体积。在三电极条件下,以0.5 mol/L H_2SO_4为电解液,富缺陷晶态WSe_2纳米片在10 mA·cm~(-2)时的过电位仅为277 mV,远低于未剥离的WSe_2材料(385 mV)。此外,富缺陷晶态WSe_2纳米片的Tafel斜率(58 mV·dec~(-1))也明显低于剥离前的WSe_2(81 mV·dec~(-1))催化剂。虽然富缺陷晶态WSe_2纳米片的析氢催化活性与商用Pt/C (20%)贵金属材料相比仍有一定差距,但其成本较低,在大规模电解水制氢产业中仍有重要应用价值。交流阻抗测试进一步表明,富缺陷晶态WSe_2纳米片具有更低的电荷转移电阻,可有效提升析氢反应的电极动力学过程。长时间电解水析氢测试表明,富缺陷晶态WSe_2纳米片不仅具有高的析氢催化活性,还具有良好的电化学稳定性。富缺陷晶态WSe_2纳米片卓越的电化学性能主要得益于以下两点:一方面,超声剥离减小了催化剂的尺寸、增加了比表面积、拓宽了孔径分布,形成了富缺陷的WSe_2结构;另一方面,较高的结晶性使材料能够抵御电化学腐蚀,在析氢反应中表现出良好的稳定性。     

复合电沉积制备（Ni-Mo）-TiO2电极及其电催化析氢性能

为开发新型廉价高效的析氢材料,用恒电流复合电沉积方法制备了(Ni-Mo)-TiO2复合电极,讨论了TiO2悬浮量和电沉积时间对电极催化析氢性能的影响.用XRD和SEM对电极的晶体结构和表面形貌进行了表征,以稳态极化曲线对电极的催化析氢特性进行了评价.结果表明,(Ni-Mo)-TiO2电极是纳米TiO2粒子相和纳米晶Ni-Mo固溶体相构成的复合电极.电极具有较高的催化析氢活性.在25℃、0.5mol.dm-3H2SO4溶液中其表观交换电流密度是Ni-Mo合金电极的2.6倍,是Ni电极的60倍.在电流密度为100mA·cm-2时,电极电势相对于Ni-Mo电极正移了120mV,相对于Ni电极正移了542mV.催化活性的提高源于反应机理的改变,表观活化吉布斯自由能相对于Ni-Mo合金电极降低了24.48kJ·mol-1.     

NiS2@MoS2/CC纳米复合材料的制备及其电催化析氢性能的研究

电解水产氢是近来研究的热点,电极催化材料是影响析氢反应的重要因素。通过两步水热法,成功在碳布上合成了NiS_2@MoS_2三维异质结构复合催化剂(NiS_2@MoS_2/CC)。在碳布上垂直排列的NiS_2纳米片为MoS_2提供了良好的支撑,在暴露更多边缘活性位点的同时,也为析氢反应提供了快速的物质传输通道。合理的界面设计促使NiS_2和MoS_2发挥协同作用,改善催化剂表面电子状态,从而体现出更好的析氢催化活性。电化学测试表明,NiS_2@MoS_2/CC具有较大的电化学活性面积,在碱性条件下驱动10mA/cm~2析氢反应电流密度的过电位为106 mV,Tafel斜率为61.1 mV/dec,远优于单一的MoS_2/CC和NiS_2/CC催化材料。     

气-热液反应技术制备硫化镍及电催化性能研究

以乙酰丙酮镍(NiC_(10)H_(14)O_4)为镍源,硫化氢(H2S)为硫源,采用气-热液反应技术(Hot-bubbling)制得硫化镍(NiS)纳米晶。将NiS纳米晶修饰到玻碳电极上,并对NiS纳米晶的电催化性能进行了研究。采用扫描电子显微镜(SEM)、X射线衍射(XRD)、透射电子显微镜-能量分散光谱(TEM-EDX)分别对NiS纳米晶的形貌、尺寸及结构等进行了表征。利用线性扫描伏安法、循环伏安法,交流阻抗等电化学技术对材料在酸性条件下对水的电化学析氢性能进行研究。结果表明:采用Hot-bubbling法制得的NiS纳米晶结晶度高,双电层为28.8mF/cm~2,表明修饰后电极有较大的表面积,在0.5mol稀硫酸电解质溶液中,塔菲尔(tafel)斜率为42.7283mV/dec,有较好的电析氢催化效果。     

Metal–Organic-Framework-Derived Co2P Nanoparticle/Multi-Doped Porous Carbon as a Trifunctional Electrocatalyst

Developing efficient and low-cost replacements for precious metals as electrocatalysts active in electrochemical reactions—the oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR)—is a top priority in renewable energy technology. In this work a highly active and very stable trifunctional electrocatalyst composed of Co₂P embedded in Co, N, and P multi-doped carbon has been synthesized using zeolitic imidazolate frameworks as precursors. The synergistic effects between Co₂P and the multi-heteroatom-doped carbon substrates afford materials having electrocatalytic activities for HER, OER, and ORR, which are comparable—or even superior to—those of commercial RuO₂ or Pt/C catalysts. Density functional theory calculations show that Co₂P has a higher density of states at the Fermi level than Co_nP (0 < n < 2), which promotes electron transfer and intermediates adsorption in the catalytic process. Zinc–air batteries and water splitting devices assembled using the materials as electrode electrocatalysts show good performance and outstanding stability. This work represents a breakthrough in improving the catalytic performance of non-precious metal electrocatalysts for OER, HER, and ORR, and opens new avenues for clean energy generation.     

NiSe‐Ni0.85Se Heterostructure Nanoflake Arrays on Carbon Paper as Efficient Electrocatalysts for Overall Water Splitting

Fabricating cost‐effective, bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in basic media is critical for renewable energy generation. Here, NiSe/CP, Ni_0.85Se/CP, and NiSe‐Ni_0.85Se/CP heterostructure catalysts with different phase constitutions are successfully prepared through in situ selenylation of a NiO nanoflake array oriented on carbon paper (CP) by tuning the original Ni/Se molar ratio of the raw materials. The relationship between the crystal phase component and electrocatalytic activity is systematically studied. Benefiting from the synergetic effect of the intrinsic metallic state, facile charge transport, abundant catalytic active sites, and multiple electrolyte transmission paths, the optimized NiSe‐Ni_0.85Se/CP exhibits a remarkably higher catalytic activity for both the HER and OER than single‐phase NiSe/CP and Ni_0.85Se/CP. A current density of 10 mA cm⁻² at 1.62 V and a high stability can be obtained by using NiSe‐Ni_0.85Se/CP as both the cathode and anode for overall water splitting under alkaline conditions. Density functional theory calculations confirm that H and OH⁻ can be more easily adsorbed on NiSe‐Ni_0.85Se than on NiSe and Ni_0.85Se. This study paves the way for enhancing the overall water splitting performance of nickel selenides by fabricating heterophase junctions using nickel selenides with different phases.     

Highly Efficient Hydrogen Evolution from a Mesoporous Hybrid of Nickel Phosphide Nanoparticles Anchored on Cobalt Phosphosulfide/Phosphide Nanosheet Arrays

Facile design of low‐cost and high‐efficiency catalysts with earth‐abundant and cheap materials is desirable to replace platinum (Pt) for the hydrogen evolution reaction (HER) in water splitting, but the development of such HER catalysts with Pt‐like activity using simple strategies remains challenging. A mesoporous hybrid catalyst of nickel phosphides nanoparticles and cobalt phosphosulfide/phosphide (CoS|Ni|P) nanosheet arrays for HER is reported here, which is developed by a facile three‐step approach consisting of electrodeposition, thermal sulfurization, and phosphorization. This hybrid catalyst is highly robust and stable in acid for HER, and is distinguished by very low overpotentials of 41, 88, and 150 mV to achieve 10, 100, and 1000 mA cm^?2, respectively, as well as a small Tafel slope (45.2 mV dec^?1), and a large exchange current density (964 µA cm^?2). It is among the most efficient earth‐abundant catalysts reported thus far for HER. More importantly, this electrocatalyst has electrochemical durability over 20 h under a wide range of current densities (up to 1 A cm^?2) in acidic conditions, as well as very high turnover frequencies of 0.40 and 1.26 H₂ s^?1 at overpotentials of 75 and 100 mV, respectively, showing that it has great potential for practical applications in large‐scale water electrolysis.     

Active Sites Intercalated Ultrathin Carbon Sheath on Nanowire Arrays as Integrated Core–Shell Architecture: Highly Efficient and Durable Electrocatalysts for Overall Water Splitting

The development of active bifunctional electrocatalysts with low cost and earth‐abundance toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) remains a great challenge for overall water splitting. Herein, metallic Ni₄Mo nanoalloys are firstly implanted on the surface of NiMoO_x nanowires array (NiMo/NiMoO_x ) as metal/metal oxides hybrid. Inspired by the superiority of carbon conductivity, an ultrathin nitrogen‐doped carbon sheath intercalated NiMo/NiMoO_x (NC/NiMo/NiMoO_x ) nanowires as integrated core–shell architecture are constructed. The integrated NC/NiMo/NiMoO_x array exhibits an overpotential of 29 mV at 10 mA cm^?2 and a low Tafel slope of 46 mV dec^?1 for HER due to the abundant active sites, fast electron transport, low charge‐transfer resistance, unique architectural structure and synergistic effect of carbon sheath, nanoalloys, and oxides. Moreover, as OER catalysts, the NC/NiMo/NiMoO_x hybrids require an overpotential of 284 mV at 10 mA cm^?2. More importantly, the NC/NiMo/NiMoO_x array as a highly active and stable electrocatalyst approaches ≈10 mA cm^?2 at a voltage of 1.57 V, opening an avenue to the rational design and fabrication of the promising electrode materials with architecture structures toward the electrochemical energy storage and conversion.     

Significantly Stabilizing Hydrogen Evolution Reaction Induced by Nb-Doping Pt/Co(OH)2 Nanosheets

High stability and efficiency of electrocatalysts are crucial for hydrogen evolution reaction (HER) toward water splitting in an alkaline media. Herein, a novel nano-Pt/Nb-doped Co(OH)₂ (Pt/Nb Co(OH)₂) nanosheet is designed and synthesized using water-bath treatment and solvothermal reduction approaches. With nano-Pt uniformly anchored onto Nb Co(OH)₂ nanosheet, the synthesized Pt/Nb Co(OH)₂ shows outstanding electrocatalytic performances for alkaline HER, achieving a high stability for at least 33 h, a high mass activity of 0.65 mA µg⁻¹ Pt, and a good catalytic activity with a low overpotential of 112 mV at 10 mA cm⁻². Both experimental and theoretical results prove that Nb-doping significantly optimizes the hydrogen adsorption free energy to accelerate the Heyrovsky step for HER, and boosts the adsorption of H₂O, which further enhances the water activation. This study provides a new design methodology for the Nb-doped electrocatalysts in an alkaline HER field by facile and green way.     

Synthesis and characterization of LiCo0.3−xGaxNi0.7O2 (x = 0, 0.05) as a cathode material for lithium ion battery

The single phase of LiCo_0.3−xGa_xNi_0.7O₂ (x = 0, 0.05) was synthesized by a sol–gel method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical performance. The powders are homogeneous and have a good-layered structure. The synthesized LiCo_0.25Ga_0.05Ni_0.7O₂ exhibits better electrochemical performance with an initial discharge capacity of 180.0 mAh g⁻¹ and a capacity retention of 95.2% after 50 cycles between 2.8 and 4.4 V at 0.2C rate. The study on the structural evolution of the material during the cycling shows that Ga-doping improves the structure stability of LiCo_0.3Ni_0.7O₂ at ambient temperature and 55 °C. Meanwhile, Ga-doping not only suppresses the alternating current (AC) impedance of LiCo_0.3Ni_0.7O₂ but also promotes the Li⁺ diffusion in LiCo_0.3Ni_0.7O₂. Furthermore, thermal stability of the charged LiCo_0.25Ga_0.05Ni_0.7O₂ is improved, which may be attributed to the retard of O₂ evolution in LiCo_0.3Ni_0.7O₂ and the suppression of electrolyte oxidation during cycling by Ga-doping_.     

Nickel–Cobalt Diselenide 3D Mesoporous Nanosheet Networks Supported on Ni Foam: An All‐pH Highly Efficient Integrated Electrocatalyst for Hydrogen Evolution

Novel 3D Ni_1?x Co_x Se₂ mesoporous nanosheet networks with tunable stoichiometry are successfully synthesized on Ni foam (Ni_1?x Co_x Se₂ MNSN/NF with x ranging from 0 to 0.35). The collective effects of special morphological design and electronic structure engineering enable the integrated electrocatalyst to have very high activity for hydrogen evolution reaction (HER) and excellent stability in a wide pH range. Ni_0.89Co_0.11Se₂ MNSN/NF is revealed to exhibit an overpotential (η₁₀) of 85 mV at ?10 mA cm^?2 in alkaline medium (pH 14) and η₁₀ of 52 mV in acidic solution (pH 0), which are the best among all selenide‐based electrocatalysts reported thus far. In particular, it is shown for the first time that the catalyst can work efficiently in neutral solution (pH 7) with a record η₁₀ of 82 mV for all noble metal‐free electrocatalysts ever reported. Based on theoretical calculations, it is further verified that the advanced all‐pH HER activity of Ni_0.89Co_0.11Se₂ is originated from the enhanced adsorption of both H⁺ and H₂O induced by the substitutional doping of cobalt at an optimal level. It is believed that the present work provides a valuable route for the design and synthesis of inexpensive and efficient all‐pH HER electrocatalysts.     

Ultrafast Formation of Amorphous Bimetallic Hydroxide Films on 3D Conductive Sulfide Nanoarrays for Large‐Current‐Density Oxygen Evolution Electrocatalysis

Developing nonprecious oxygen evolution electrocatalysts that can work well at large current densities is of primary importance in a viable water‐splitting technology. Herein, a facile ultrafast (5 s) synthetic approach is reported that produces a novel, efficient, non‐noble metal oxygen‐evolution nano‐electrocatalyst that is composed of amorphous Ni–Fe bimetallic hydroxide film‐coated, nickel foam (NF)‐supported, Ni₃S₂ nanosheet arrays. The composite nanomaterial (denoted as Ni‐Fe‐OH@Ni₃S₂/NF) shows highly efficient electrocatalytic activity toward oxygen evolution reaction (OER) at large current densities, even in the order of 1000 mA cm^?2. Ni‐Fe‐OH@Ni₃S₂/NF also gives an excellent catalytic stability toward OER both in 1 m KOH solution and in 30 wt% KOH solution. Further experimental results indicate that the effective integration of high catalytic reactivity, high structural stability, and high electronic conductivity into a single material system makes Ni‐Fe‐OH@Ni₃S₂/NF a remarkable catalytic ability for OER at large current densities.     

Phase Segregation in Cu0.5Ni0.5 Alloy Boosting Urea-Assisted Hydrogen Production in Alkaline Media

Coupling urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) is promising for energy-efficient hydrogen production. However, developing cheap and highly active bifunctional electrocatalysts for overall urea electrolysis remains challenging. In this work, a metastable Cu_0.5Ni_0.5 alloy is synthesized by a one-step electrodeposition method. It only requires the potentials of 1.33 and −28 mV to obtain the current density of ±10 mA cm⁻² for UOR and HER, respectively. The metastable alloy is considered to be the main reason causing the above excellent performances. In the alkaline medium, the as-prepared Cu_0.5Ni_0.5 alloy exhibits good stability for HER; and conversely, NiOOH species can be rapidly formed during the UOR due to the phase segregation of Cu_0.5Ni_0.5 alloy. In particular, for the energy-saving hydrogen generation system coupled with HER and UOR, only 1.38 V of voltage is needed at 10 mA cm⁻²; and at 100 mA cm⁻², the voltage decreases by ≈305 mV compared with that of the routine water electrolysis system (HER || OER). Compared with some catalysts reported recently, the Cu_0.5Ni_0.5 catalyst owns superior electrocatalytic activity and durability. Furthermore, this work provides a simple, mild, and rapid method for designing highly active bifunctional electrocatalysts toward urea-supporting overall water splitting.     

Surface Spin Enhanced High Stable NiCo2S4 for Energy-Saving Production of H2 from Water/Methanol Coelectrolysis at High Current Density

Nickel based materials are promising electrocatalysts to produce hydrogen from water in alkaline media. However, the stability is of great challenge, limiting its practical material functions. Herein, a new technique for electro-deposition flower-like NiCo₂S₄ nanosheets on carbon-cloth (CC@NiCo₂S₄) is proposed for energy-saving production of H₂ from water/methanol coelectrolysis at high current density by constructing array architectures and regulating surface magnetism. The optimized and fine-tuned magnetism on the surface of the electrochemical in situ grown CC@NiCo₂S₄ nanosheet array result in (0 1 −1) surface universally exposed, high catalytic activity for methanol electrooxidation, and long-term stability at high current density. X-ray photoelectron spectroscopy in combination of density functional theory calculations confirm the valence electron states and spin of d electrons for the surface of NiCo₂S₄, which enhance the surface stability of catalysts. This technology may be utilized to alter the surface magnetism and increase the stability of Ni-based electrocatalytic materials in general.