Electrochemical nitrogen reduction: identification and elimination of contamination in electrolyte

Laiquan Li, Cheng Tang, Dazhi Yao, Yao Zheng, Shi-Zhang Qia

Co (II) boron imidazolate framework with rigid auxiliary linkers for stable electrocatalytic oxygen evolution reaction

Metal–organic frameworks (MOFs) have significant potential for practical application in catalysis. However, many MOFs are shown to be sensitive to aqueous solution. This severely limits application of MOFs in electrocatalytic operations for energy production and storage. Here, a Co (II) boron imidazolate framework CoB(im)4(ndc)0.5 (BIF‐91, im = imidazolate, ndc = 2,6‐naphthalenedicarboxylate) that is rationally designed and successfully tested for electrocatalytic application in strong alkaline (pH ≈ 14) solution is reported. In such a BIF system, the inherent carboxylate species segment large channel spaces into multiple domains in which each single channel is filled with ndc ligands through the effect of zeolite channel confinement. These ligands, with strong CH···π interaction, act as a rigid auxiliary linker to significantly enhance the structural stability of the BIF‐91 framework. Additionally, the π‐conjugated effect in BIF‐91 stabilizes dopant Fe (III) at the atomic scale to construct Fe‐immobilized BIF‐91 (Fe@BIF‐91). Due to the synergistic effect between Fe (III) guest and Co (II) in the framework, the Fe@BIF‐91 acts as an active and stable electrocatalyst for the oxygen evolution reaction in alkaline solution.Tian Wen, Yao Zheng, Jian Zhang, Kenneth Davey, Shi‐Zhang Qia

High electrocatalytic hydrogen evolution activity of an anomalous ruthenium catalyst

Hydrogen evolution reaction (HER) is a critical process due to its fundamental role in electrocatalysis. Practically, the development of high-performance electrocatalysts for HER in alkaline media is of great importance for the conversion of renewable energy to hydrogen fuel via photoelectrochemical water splitting. However, both mechanistic exploration and materials development for HER under alkaline conditions are very limited. Precious Pt metal, which still serves as the state-of-the-art catalyst for HER, is unable to guarantee a sustainable hydrogen supply. Here we report an anomalously structured Ru catalyst that shows 2.5 times higher hydrogen generation rate than Pt and is among the most active HER electrocatalysts yet reported in alkaline solutions. The identification of new face-centered cubic crystallographic structure of Ru nanoparticles was investigated by high-resolution transmission electron microscopy imaging, and its formation mechanism was revealed by spectroscopic characterization and theoretical analysis. For the first time, it is found that the Ru nanocatalyst showed a pronounced effect of the crystal structure on the electrocatalytic activity tested under different conditions. The combination of electrochemical reaction rate measurements and density functional theory computation shows that the high activity of anomalous Ru catalyst in alkaline solution originates from its suitable adsorption energies to some key reaction intermediates and reaction kinetics in the HER process.Yao Zheng, Yan Jiao, Yihan Zhu, Lu Hua Li, Yu Han, Ying Chen, Mietek Jaroniec and Shi-Zhang Qia

Revealing the origin of improved reversible capacity of dual-shell bismuth boxes anode for potassium-Ion batteries

Nanostructured alloy anodes have been successfully used in several kinds of rocking-chair batteries. However, a full picture of the origin of their improved reversible capacity remains elusive. Here, we combine operando synchrotron-based X-ray powder diffraction and ex situ X-ray absorption near-edge structure spectroscopy to study the double-shell structured bismuth boxes as anodes in potassium-ion batteries to reveal the origin of their improved capacity. The nanostructured bismuth anode offers an enhanced capability to tolerate the volume expansion under a low current density of 0.2 C, resulting in a more complete alloy reaction. Additionally, under a high current density of 2 C, nanostructured bismuth anode with larger surface area offers more sites to electrochemically alloy with potassium and results in a lower average oxidation state of bismuth. These findings offer guidance for the rational design and engineering of electrode materials according to the current density for rocking-chair batteries.Fangxi Xie, Lei Zhang, Biao Chen, Dongliang Chao, Qinfen Gu, Bernt Johannessen, Mietek Jaroniec, and Shi-Zhang Qia

Directed Urea-to-Nitrite Electrooxidation via Tuning Intermediate Adsorption on Co, Ge Co-Doped Ni Sites

OnlinePublThe electrochemical urea oxidation reaction (UOR) is an alternative to electrooxidation of water for energy–saving hydrogen (H₂) production. To maximize this purpose, design of catalysts for selective urea-to-nitrite (NO₂‾ ) electrooxidation with increased electron transfer and high current is practically important. Herein, a cobalt, germanium (Co, Ge) co-doped nickel (Ni) oxyhydroxide catalyst is reported first time that directs urea-to-NO₂‾ conversion with a significant Faradaic efficiency of 84.9% at 1.4 V versus reversible hydrogen electrode and significantly boosts UOR activity to 448.0 mA cm−2. Importantly, this performance is greater than for most reported Ni-based catalysts. Based on judiciously combined synchrotron-based measurement, in situ spectroscopy and density functional theoretical computation, significantly boosted urea-to-NO2 – production results from Co, Ge co-doping is demonstrated that optimizes electronic structure of Ni sites in which urea adsorption is altered as NO-terminal configuration to facilitate C-N cleavage for *NH formation, and thereby expedites pathway for urea to NO₂‾ conversion. Findings highlight the importance of tuning intermediate adsorption behavior for design of high-performance UOR electrocatalysts, and will be of practical benefit to a range of researchers and manufacturers in replacing conventional water electrooxidation with UOR for energy-saving H₂ production.Pengtang Wang, Xiaowan Bai, Huanyu Jin, Xintong Gao, Kenneth Davey, Yao Zheng, Yan Jiao, and Shi-Zhang Qia

How to explore ambient electrocatalytic nitrogen reduction reliably and insightfully

The efficient activation of dinitrogen for the production of ammonia plays a crucial role in our modern society, considering the significant impact of ammonia on food, chemicals, and energy. As an attractive alternative to the century-old Haber-Bosch process which is responsible for 1-2% of global energy consumption, utilization of half the hydrogen produced globally, and ∼1% of global energy-related CO2 emissions, the ambient electrocatalytic nitrogen reduction reaction has attracted tremendous interest during the past few years. Some achievements have revealed the possibility of this process, but have also identified great challenges. The activity and selectivity of the nitrogen reduction reaction are fundamentally limited by competing hydrogen evolution and nitrogen scaling relations, while low production rates and ubiquitous contaminants plague experimental practices. Aiming toward higher accuracy and reproducibility of claimed results, and more meaningful, impactful, and insightful research, this tutorial review summarizes the present status and challenges in the study of ambient electrocatalytic nitrogen reduction, followed by a thorough discussion of various experimental parameters. We then recommend a series of protocols and best practices for experiments, and also highlight some potential directions for future research in this exciting and important field.Cheng Tang, Shi-Zhang Qia

Toward high-voltage aqueous batteries: super- or low-concentrated electrolyte?

Abstract not available.Dongliang Chao and Shi-Zhang Qia

Recent progress in engineering the atomic and electronic structure of electrocatalysts via cation exchange reactions

In the past few decades, tremendous advances have been made in electrocatalysis due to the rational design of electrocatalysts at the nanoscale level. Further development requires engineering electrocatalysts at the atomic level, which is a grand challenge. Here, the recent advances in cation exchange strategy, which is a powerful tool for fine-tuning atomic structure of electrocatalysts via surface faceting, heteroatom doping, defects formation, and strain modulation, are the main focus. Proper atomic structure engineering effectively adjusts the electronic structure, and thus enhances the electronic conductivity and facilitates the adsorption/desorption of reaction intermediates. By virtue, the cation exchange strategy greatly boosts the intrinsic and apparent activities of electrocatalysts and shows a great potential toward design of new energy conversion devices, such as water splitting devices and metal-air batteries. It is believed that cation exchange offers new insights and opportunities for the rational design of a new generation of electrocatalysts.Tao Ling, Mietek Jaroniec, and Shi-Zhang Qia

Isolated boron sites for electroreduction of dinitrogen to ammonia

Exploring electrocatalysts with high activity is essential for the production of ammonia via an electrochemical routine. By employing density functional theory calculations, we investigated the electrochemical nitrogen reduction reaction (eNRR) activity on binary metal borides, a model system of metal borides. To elaborate the mechanisms, molybdenum borides (Mo2B, α-MoB, and MoB2) were first modeled; the results indicate that the crystal structures greatly impact the N2 adsorption and therefore the electrocatalytic activity. Our electronic structure investigation suggests that boron p-orbital hybrids with dinitrogen π*-orbital, and the population on p−π*-orbital determine the N2 adsorption strength. Therefore, the isolated boron site of Mo2B with less filled pz-orbital benefits the activation of N2 and weaken the triple bond of dinitrogen. This isolated boron sites concept was successfully extended to other metal borides in the form of M2B (M stands for Ti, Cr, Mn, Fe, Co, Ni, Ta, W). Mo2B, Fe2B, and Co2B were discovered as the most promising candidates with low limiting potentials due to appropriate adsorption strength of reaction intermediates led by moderate pz filling. This work provides insights for designing metal borides as promising eNRR electrocatalysts.Xin Liu, Yan Jiao, Yao Zheng and Shi-Zhang Qia

Comparative analysis of structural and morphological properties of large-pore periodic mesoporous organosilicas and pure silicas

10.1021/jp047479sJournal of Physical Chemistry B1084216441-16450JPCB