焦耳热快速合成双功能电催化剂用于高效水分解

电解水是有效的产氢方式之一, 开发具有高催化活性的电极材料是当前电解水的研究热点,但仍面临诸多挑战。 本研究报告了一种通过焦耳热技术快速制备多金属异质结构, 并将其用作电解水的双功能电催化剂, 展现出优异的电解水催化活性。通过焦耳热处理三种金属前驱涂覆的碳布, Mo₂C和CoO/Fe₃O₄异质结构形成。当其用作析氢（HER）和析氧（OER）的双功能催化剂时, 仅需121 mV和268 mV的过电位,可以实现10 mA·cm^-2的电流密度。当用于两电极电解水时, MoC/FeO/CoO/CC作为阳极和阴极催化剂表现出优异的电催化性能和长期稳定性, 仅需1.69 V即可实现10 mA·cm^-2的电流密度, 并且展现出25小时的稳定性。本研究通过简单、 快速的焦耳热技术实现了双金属/多金属异质结构的构筑,并应用于高效水电解,为合理设计多金属异质结构提供指导。     

三维百合花状的CoNi_2S_4作为先进的双功能电催化剂用于氢析出和氧析出反应（英文）

为简化电解水催化剂的合成过程和优化电解水操作系统,双功能电解水催化剂的研究,特别是在碱性条件下同时具有优异催化氢析出和氧析出反应性能的双功能电催化剂的研究尤为重要.其中,过渡金属硫化物,特别是CoNi硫化物,被报道有与氢化酶类似的催化活性中心,从而具有优异的催化氢析出和催化氧析出反应性能.虽然有关对过渡金属硫化物的研究很多,但主要集中在具有一维纳米线和二维纳米片形貌结构的过渡金属硫化物.不幸的是,这些形貌结构的过渡金属硫化物在电催化过程中容易聚集和受限于电荷传输能力.三维纳米结构的材料具有较大的比表面积以分布更多的活性位点和拥有良好的电子传输能力,所以,开发三维纳米结构的过渡金属硫化物材料可能是改进其催化电解水性能的一个好途径.本文采用简单的两步水热法,通过硫化合成的CoNi前体得到了长于泡沫镍上的三维百合花状的CoNi_2S_4(CoNi_2S_4/Ni).它只需要54 mV的过电位即可获得10 mA cm~(-2)的催化氢析出反应电流,是最好的碱性催化氢析出反应电极材料之一.它在驱动100 mA cm~(-2)的催化氧析出反应电流时也只需要328 mV的过电位.另外,把CoNi_2S_4/Ni分别作为阴极和阳极组装成双电极碱性水电解槽时,它只需要1.56 V的电压即可获取10 mA cm~(-2)的催化全电解水电流并具有良好的催化全电解水稳定性.扫描电子显微镜、透射电子显微镜和N_2吸脱附曲线测试结果表明,该三维百合花状的CoNi_2S_4/Ni的表面粗糙度高和拥有多孔特性.多孔结构的CoNi_2S_4/Ni可提供更多可接触的催化活性位点,也有利于催化过程中的电解质和生成的气体的扩散与传递.交流阻抗图谱测试结果表明,CoNi_2S_4/Ni具有良好的电子传输能力.另外,不同于前期对尖晶石结构的硫化物AB_2S_4的研究结果,XPS结果表明,CoNi_2S_4/Ni中含有Ni~(б+)和S~(б–)活性物种,表明CoNi_2S_4具有与活性氢化酶类似的活性中心.Ni~(δ+)和S~(δ–)可分别作为氢氧根和质子的接收体,协助促进吸附的水分子的分离,从而提高材料的催化性能.所以,Ni~(δ+)和S~(δ–)活性物种的出现,大比表面积的三维百合花状多孔结构和良好的电荷传输能力等特性集合于CoNi_2S_4/Ni上使得CoNi_2S_4/Ni具有优异的催化氢析出和催化氧析出反应性能.     

Hierarchical Rhree-dimensional CoNi LDH-Ni3S2 Supported on Ni Foam as a Stable and Efficient Electrocatalytic Material for Overall Water Splitting

Herein, a novel self-supporting three-dimensional nanostructured CoNi LDH-Ni₃S₂ catalyst was generated in a two-step process combining hydrothermal synthesis and high-temperature electrodeposition techniques. The CoNi LDH-Ni₃S₂/NF electrode exhibits superior electrocatalytic performance with low overpotentials of 193 and 382 mV in 1 M KOH to drive a high current density of 100 mA cm⁻² for HER and OER, respectively. Meanwhile, a small cell voltage of 1.51 V was obtained upon using CoNi LDH-Ni₃S₂/NF as a dual-functional catalyst. Additionally, CoNi LDH-Ni₃S₂/NF exhibits high stability with almost no change in HER and OER overpotentials and electrocatalytic total decomposition of water within 80,000 s.     

Cobalt and nitrogen codoped porous carbon as superior bifunctional electrocatalyst for oxygen reduction and hydrogen evolution reaction in alkaline medium

Metal (cobalt)/nitrogen codoped carbon was first fabricated by pyrolysis of coordinated “noncarbonizable” polymer as bifunctional catalyst for ORR and HER, which showed better electrocatalytic performances than most bifunctional doped carbon catalysts in alkaline electrolyte.     

Molybdenum-doped titanium dioxide supported low-Pt electrocatalyst for highly efficient and stable hydrogen evolution reaction

The Platinum(Pt)-based catalysts exhibit excellent catalytic performance for the hydrogen evolution reaction(HER) while suffering from poor stability due to the weak interaction between the carbon support and Pt.Herein,a molybdenum-doped titanium dioxide(Ti_(0.9)Mo_(0.1)O_2) supported low-Pt electrocatalyst with stronger interaction between catalyst and support is applied to tune the electrocatalytic performance of Pt.The Ti_(0.9)Mo_(0.1)O_2 support can not only tolerate the corrosion environment in the catalytic system,but also generate strong metal-support inte raction(SMSI) between the oxide and catalyst.A facile solvothermal method is used to prepare Ti_(0.9)Mo_(0.1)O_2 as support to anchor Pt nanoparticles.The 5% Pt supported on Ti_(0.9)Mo_(0.1)O_2 catalyst exhibits 4.4-fold mass activity(MA) at an overpotential of 50 mV and higher stability than 20% Pt/C with only 1/4 Pt loading.The SMSI between the Ti_(0.9)Mo_(0.1)O_2 and Pt prevents the Pt aggregation to achieve excellent stability,and hydrogen spillover effect in the interface between Pt and support benefits the hydrogen production process.This work presents a novel sight for the fabrication and design of oxide supported catalysts in various catalytic system by reasonably employing support effect.     

氧还原和析氧反应的双功能电催化剂--氮磷共掺碳负载四氧化三钴

金属-空气电池具备诸多优势,譬如绿色环保、能量转化率高、启动快速、能量密度高、使用寿命和干态存储时间长等.与燃料电池相比,金属-空气电池结构简单,放电电压平稳,成本低,但依然存在一些制约发展的问题,如阴极催化剂.阴极催化剂在金属-空气电池中发挥催化氧还原反应(oxygen reduction reaction, ORR)和析氧反应(oxygen evolution reac-tion, OER)的关键作用.铂及其合金常用作 ORR的单功能催化剂,而钌和铱等是目前 OER催化效率最高的,但 ORR活性很低,因此需要开发出一种廉价而又具备双功能催化作用的催化剂.单异原子掺杂的碳基催化剂的研究集中在 ORR催化性能上,而多异原子共掺碳最近有研究表明具有双催化氧的性质,如氮磷共掺碳.在这些氮磷共掺的碳架中,氮磷共掺物起着 OER催化作用,掺氮物为 ORR催化的活性位点,而掺磷物起着强化作用.异原子掺杂负载的钴基催化剂(如掺氮还原氧化石墨烯载 Co3O4)是近年来双功能催化剂研究的另一个热点.钴基催化剂有着催化 ORR和 OER的多价价态,然而其本身导电性能差,这一缺陷可通过杂化石墨化碳来弥补,石墨化碳有着优良的导电性能.据我们所知,目前仍没有关于氮磷共掺碳负载的 Co3O4双催化氧的研究.我们合成了氮磷共掺碳(NPC)负载的 Co3O4(Co3O4/NPC),并首次探索了其氧还原和析氧性能. Co3O4/NPC合成分两步进行.首先通过三聚氰胺与植酸之间的酯化或缩聚覆盖在导电炭黑颗粒表面,在保护气氛下焙烧得到 NPC,然后经溶剂热反应以及空气中氧化合成 Co3O4/NPC.催化剂的性能综合考虑了催化活性和稳定性两方面.采用线性扫描伏安法评估了 OER和 ORR的催化活性.对于 OER, Co3O4/NPC的起始电势是0.54 V (以饱和甘汞电极为参比电极),在0.80 V时电流密度达到21.95 mA/cm2,均优于 Co3O4/C和 NPC. Co3O4/NPC的高效 OER催化可归因于氮磷共掺物与 Co3O4之间的协同作用.对于 ORR, Co3O4/NPC的催化效率与商用 Pt/C相近,它们的扩散极限电流密度分别为–4.49和–4.76 mA/cm2(E =–0.80 V).在 ORR过程中, Co3O4起到主要的催化作用.采用计时电流(电流-时间)法评估了催化剂的稳定性.经6 h测定,对于 OER, Co3O4/NPC剩46%电流;而对于 ORR,剩95%电流.整体而言, Co3O4/NPC在 OER和 ORR中都表现出高的催化效率以及良好的稳定性.     

High-performance electrocatalyst of vanadium-iron bimetal organic framework arrays on nickel foam for overall water splitting

The development of active,low-cost and durable bifunctional electrocatalysts toward both oxygen evolution reaction(OER) and hydro gen evolution react ion(HER) a re important for overall water splitting.Here,well-defined arrays of vanadium-iron bimetal organic frameworks(VFe-MOF) with controllable stoichiometry have been successfully prepared on nickel foam(NF).The as-fabricated VFe-MOF@NF electrode exhibits excellent electrocatalytic activity and durability for OER and HER in alkaline medium.The material's overpotentials of 10 mA/cm~2 are 246 mV for OER and 147 mV for HER,respectively.The electrolyzer made from the VFe-MOF@NF electrodes as both the cathode and anode in 1 mol/L KOH needs only a voltage of 1.61 V to reach a current density of 10 mA/cm~2.The superior performance of VFeMOF@NF can be attributed to the morphological control and electronic regulation of the bimetals,that is,1) the exposure of the active sites at electrocatalyst/electrolyte interfaces due to the array structure;2)the synergistic effect of vanadium and iron metals on electro-catalyzing the overall water splitting.     

Co1-xS embedded in porous carbon derived from metal organic framework as a highly efficient electrocatalyst for oxygen evolution reaction

Here, we report a two-step conversion method to fabricate a composite of Co_1-xS embedded in porous carbon framework (Co_1-xS@C) derived from metal organic frameworks (MOFs). The as-prepared porous dodecahedron Co_1-xS@C composite catalyst exhibits excellent electrocatalytic performance towards oxygen evolution reaction (OER).     

The preparation of ionic liquid based iron phosphate/CNTs composite via microwave radiation for hydrogen evolution reaction and oxygen evolution reaction

Water electrolysis is a promising method for hydrogen production, so the preparation of low-cost and efficient electrocatalysts with a quick and simple procedure is crucial. Herein, iron phosphate (Fe₇(PO₄)₆) was prepared via microwave radiation using ionic liquid (IL) as iron and phosphorus dual-source. This method is simple and rapid, and the product can be directly used as electrocatalysts without further treatment. The experimental results show that the IL can influence the morphology and electrocatalytic performance. Moreover, the addition of carbon nanotubes (CNTs) is favorable for formation of iron phosphate nanoparticles to improve the catalytic activities. As hydrogen evolution reaction (HER) catalyst, this iron phosphate/CNTs exhibits an onset overpotential of 120 mV, Tafel slope of 32.9 mV dec^-1, and current densities of 10 mA cm⁻² at overpotential of 185 mV. Then, it obtains a good activity for oxygen evolution reaction (OER) with a low onset potential of 1.48 V, Tafel slope of 73.3 mV dec^-1, and it only needs an overpotential of 300 mV to drive the 10 mA cm⁻². This bifunctional catalyst also shows good durability for HER and OER. This microwave-assisted method provides an outstanding strategy to prepare iron phosphate in a simple and fast process with good catalytic performance for water splitting.     

A novel ball-in-ball hollow oxygen-incorporating cobalt sulfide spheres as high-efficient electrocatalyst for oxygen evolution reaction

Transition-metal chalcogenides with hollow nanostructure,especially cobalt sulfides,are considered as the most pro mising non-precious metal catalysts for oxygen evolution reactio n.However,it is difficult to synthesize oxygen-containing cobalt sulphides with hollow structure due to the different physical/chemical properties between metal sulfides and metal cobalts.Herein,we report a novel oxygencontaining amorphous cobalt sulfide ball-in-ball hollow sphere s(Co-S-O BBHS) synthesized by an anion exchange method.Taking advantage of the ball-in-ball hollow structure,the amorphous Co-S-O BBHS shows supe rior oxygen evolution reaction(OER) electrocatalytic performance with a low overpotentiat of285 mV at 10 mA/cm~2,small Tafel slope of 49.67 mV/dec,high Faraday efficiency of 96%,and satisfied durability.Experiments and DFT calculations demonstrate that the introduction of oxygen and sulfur modulates the electronic structure of Co-S-O BBHS,thus enhancing the adsorption of *0(adsorbed 0 species on catalyst surface) intermediate,which greatly boosts the catalytic activity towards OER.This work provides a new strategy for controllable synthe sis of complex hollow structures of transition-metal chalcogenides for OER.     

Implanting Ni into N-doped puffed carbon: A new advanced electrocatalyst for oxygen evolution reaction

Tailored design and synthesis of high-quality electrocatalysts is vital for the advancement of oxygen evolution reaction (OER). Herein, we report a powerful puffing method to fabricate hierarchical porous N-doped carbon with numerous embedded Ni nanoparticles. Interestingly, during the puffing and annealing process, rice precursor with N and Ni sources can be in-situ converted into Ni-embedded N-doped porous carbon (N-PC/Ni) composite. The obtained N-PC/Ni composite possesses a cross-linked porous architecture containing conductive carbon backbone and active Ni nanoparticles electrocatalysts for OER. The pore formation in N-PC/Ni composite is also proposed because of carbothermic reduction. The N-PC/Ni composite is fully studied as electrocatalysts for OER. Due to increased active surface area, enhanced electronic conductivity and reactivity, the designed N-PC/Ni composite exhibits superior OER performance with a low Tafel slope (∼88 mV/dec) and a low overpotential as well as excellent long-term stability in alkaline solution. Our proposed rational design strategy may provide a new way to construct other advanced metal/heteroatom-doped composites for widespread application in electrocatalysis.     

Nanostructured NiMoO4 as active electrocatalyst for oxygen evolution

Hydrothermally synthesized NiMoO₄ nanorods exhibit considerable electrocatalytic properties for the oxygen evolution in alkaline condition. The performance enhancement of ternary NiMoO₄ over binary oxide NiO and MoO₃ is attributed to the inclusion of Mo that promotes the pre-redox reaction of Ni to form active Ni species.