调控氧空位实现高比表面积Co3O4纳米片上的产氧反应

Electrochemical water splitting requires efficient water oxidation catalysts to accelerate the sluggish kinetics of water oxidation reaction. Here, we designed an efficient Co₃O₄ electrocatalyst using a pyrolysis strategy for oxygen evolution reaction (OER). Morphological characterization confirmed the ultra-thin structure of nanosheet. Further, the existence of oxygen vacancies was obviously evidenced by the X-ray photoelectron spectroscopy and electron spin resonance spectroscopy. The increased surface area of Co₃O₄ ensures more exposed sites, whereas generated oxygen vacancies on Co₃O₄ surface create more active defects. The two scenarios were beneficial for accelerating the OER across the interface between the anode and electrolyte. As expected, the optimized Co₃O₄ nanosheets can catalyze the OER efficiently with a low overpotential of 310 mV at current density of 10 mA/cm² and remarkable long-term stability in 1.0 mol/L KOH.     

Common Pitfalls of Reporting Electrocatalysts for Water Splitting

Rigorous assessment of heterogeneous electrocatalysts for electrochemical water splitting has been a critical issue mainly due to insufficient standard protocols to measure and report experimental data. In this perspective, we highlight some common pitfalls when measuring and reporting electrocatalytic data, which should be avoided to ensure the accuracy and reproducibility and to advance the water splitting field. We advocate to prevent the introduction of artefacts from the counter and reference electrodes, as well as the impurities in the electrolyte when conducting electrocatalyst activity measurements. In addition, we encourage the use of the electrochemically active surface area(ECSA)-normalized current densities to represent the intrinsic activity of the reported catalysts for a better comparison with previously known materials. Suitable ECSA measurement methods should be employed based on the nature of catalysts. Recommendations made in this perspective will hopefully assist in identifying advanced catalysts for water splitting research.     

The adjacent Fe oxidation greatly enhancing OER activity on the Ni active site: S plays the role in optimizing local coordination and electronic structure

Oxygen evolution reaction (OER) is the bottleneck process of water splitting, and finding efficient, durable, low-cost, and earth-abundant electrocatalysts remains a major challenge. Here, FeNi₂-400-S is to be a promising OER electrocatalyst which exhibits a low overpotential of 214 mV at a current density of 10 mA/cm². X-ray analysis indicates that the introduction of S leads to a mismatch in bond distance between the metal-sulfur bond and the metal-metal bond, which can change the local electronic structure and favorably control the electronic oxidation. The active site position of FeNi₂-400-S has been further confirmed by DFT, which the 1OOH can stably adsorb on the Ni site of the oxidized Fe-Ni-S benefitting from the synergetic effect of the Ni site and the adjacent oxidized O on the Fe atom. Our findings demonstrate that the internal reconstruction of catalyst can make the optimization of local coordination and electronic structure, in which the in-situ generated vacancy can enable the outstanding OER performance.     

锌掺杂NiCoP多孔双层阵列电极材料的制备及电催化产氢性能

通过水热、 原位磷化及HCl选择性刻蚀的方式构建了一种在泡沫镍上生长的新型Zn掺杂NiCoP多孔双层阵列结构, 与传统的单层阵列相比, 顶层纳米叶片阵列在泡沫镍载体上的底层纳米线阵列上均匀生长, 最大限度地暴露出催化的活性位点, 提供了较大的电解液接触面积. 多孔等级结构也加速了氢气泡的释放. 结果表明, 优化后的多孔H-Zn-NiCo-P催化剂在碱性电解液(1 mol/L KOH)中展现出优异的电解水产氢性能. 该材料驱动电流密度10和100 mA/cm²所需要的过电位仅为59和156 mV, Tafel斜率为66 mV/dec, 且表现出良好的电化学稳定性.     

Ceria-promoted oxygen reduction reaction in Pd-based electrocatalysts

PdCo-ceria electrocatalyst is synthesized on carbon support in a size of a few nm by colloid method. Enhanced oxygen reduction reaction (ORR) kinetics of PdCo is observed in the presence of ceria similarly as confirmed for PtCo-ceria in a half cell experiment. In addition, there appears a positive shift of the ORR onset potential of PdCo-ceria compared to PdCo while PtCo-ceria shows no such an apparent shift of onset potential. These effects of ceria on the ORR onset potential and the ORR kinetics are more remarkable as temperature increases. To get the most of oxygen storage and supply capacity of ceria, a high temperature proton exchange membrane fuel cell (PEMFC) is fabricated using PdCo-ceria as a catalyst at the cathode. Ceria effects on the ORR of PdCo-ceria catalyst are realized in the form of higher OCV and lower Tafel slope compared to PdCo catalyst in the PEMFC single cell performance. Enhancements in both ORR kinetics and ORR onset potential are very attractive features of ceria as a co-catalyst in the development of a non-Pt ORR electrocatalyst.     

质子交换膜燃料电池Pt纳米线电催化剂研究现状

质子交换膜燃料电池(PEMFC)能直接将化学能转换为电能,具有能量转换效率高、环境友好、启动快等优点.其中电催化剂是决定PEMFC性能、寿命及成本的关键材料之一.目前所采用的Pt催化剂成本较高,是阻碍其商业化的主要因素.而Pt纳米线电催化剂的Pt利用率和催化剂活性高,抗CO毒性以及耐久性好.本文综述了Pt纳米线电催化剂的制备及其电化学催化性能的研究现状.     

Simultaneous Generation of H2O2 and Formate by Co-Electrolysis of Water and CO2 over Bifunctional Zn/SnO2 Nanodots

Hydrogen peroxide (H₂O₂) and formate are important chemicals used in various chemical manufacturing industries. One promising approach for the simultaneous production of these chemicals is coupling anodic two-electron water oxidation with cathodic CO₂ reduction in an electrolyzer using nonprecious bifunctional electrocatalysts. Herein, we report an innovative hybrid electrosynthesis strategy using Zn-doped SnO₂ (Zn/SnO₂) nanodots as bifunctional redox electrocatalysts to achieve Faradaic efficiencies of 80.6 % and 92.2 % for H₂O₂ and formate coproduction, respectively, along with excellent stability for at least 60 h at a current density of ≈150 mA cm⁻². Through a combination of physicochemical characterizations, including operando attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), isotope labeling mass spectrometry (MS)/¹H NMR and quasi-in situ electron paramagnetic resonance (EPR), with density functional theory (DFT) calculations, we discovered that the Zn dopant facilitates the coupling of *OH intermediates to promote H₂O₂ production and optimizes the adsorption of *OCHO intermediates to accelerate formate formation. Our findings offer new insights into designing more efficient bifunctional electrocatalyst-based pair-electrosynthesis system for the coproduction of H₂O₂ and formate feedstocks.     

Electrocatalytic Activity of Immobilized Co(II) on Porous Graphene Aerogels

The highly‐porous graphene aerogel (GA) with BET surface area of 810 m² g^?1 and three‐dimensional structure has been successfully fabricated using the hydrothermal technique. The modified glassy carbon electrode was then prepared by casting the graphene aerogel solution followed by immersing the GA/GCE in Co⁺² solution. The results showed that graphene aerogels improved the adsorption ability of the Co (II) ions. The electrocatalysis of oxygen evolution reaction (OER) at the Co‐GA modified glassy carbon elec‐ trode (Co‐GA/GCE) has been investigated using linear sweep voltammetry (LSV) in alkaline solution. The OER was noticeably enhanced at Co‐GA/GCE, representing a negative shift in the LSV curve at the Co‐GA/GCE compared to that obtained at the bare GCE. The high electrocatalytic activity, good reproducibility and low cost of proposed electrode provides desired characteristics of a potential candi‐ date in the industrial water electrolysis process.     

钴基类沸石咪唑酯框架材料衍生的析氧反应活性催化剂（英文）

析氧反应(OER)在能量转换和储存技术中扮演着重要角色,例如在水分解和金属空气电池中,电催化剂的发展是主要任务.本文采用钴基的类沸石咪唑酯骨架结构材料(ZIFs)作为前驱体,在氩气保护气氛下,成功制备了氮掺杂钴镍磷多孔碳多面体电催化剂(CoNiP/NC).首先,采用ZIF-67作为前驱体,将ZIF-67和六水合硝酸镍按照一定比例在乙醇溶液中搅拌30 min,达到掺杂镍的目的,然后将其在不同温度下煅烧,得到的样品在300 oC氩气保护气氛下磷化,得到最终产物.所有电催化剂均通过控制碳化和磷化作用温度获得.通过对样品ZIF-67Ni进行EDS分析,证明镍成功负载到ZIF-67上,XPS结果也证明了这一点.由扫描电镜图可以看出,前驱体ZIF-67在负载Ni之后,样品表面形貌发生明显变化,表面变得粗糙,有明显的条文.磷化后样品的XRD结果说明磷化方法是成功的,同时XPS结果表明样品中有P元素存在.从扫描电镜图片可以明显看出,样品在煅烧之后表面形貌发生明显变化,由棱角明显变为表面粗糙,但是并未发生明显的团聚现象.XPS显示,样品CoNiP/NC700(700指煅烧温度(oC))中存在钴、镍、磷、碳、氮、氧这六种元素,另外还分析了其高分辨图.结果显示,电催化剂CoNiP/NC700表现出优越的电催化效率,在碱性溶液的电流密度10 mA/cm~2条件下,其开路电压约为220 mV,过电位约为300 mV.掺杂镍之后的样品性能比煅烧ZIF-67的样品好,说明镍对于提高析氧反应效率有益;同样,磷化之后样品的OER性能也有所提高.相比较而言,对于磷化之后的样品,煅烧温度是700℃时,OER催化效率最好.磷化杂化材料优越的电催化活性是由于其强的电子耦合相互作用而产生的协同效应,在镍、磷、碳等方面具有较强的协同效应.相互联系的非定形碳不仅固定了活性碳化合物以避免聚集,而且还为电子转移提供了传导通道.对样品CoNiP/NC700进行了稳定性测试,结果表明其稳定性较好,在循环10 h之后,活性仅下降了4%.这一研究表明,该复合电催化剂可能是电催化氧化反应的一个很有前景的候选催化剂.