Ir Nanoparticles Anchored on Metal-Organic Frameworks for Efficient Overall Water Splitting under pH-Universal Conditions.

The construction of high-activity and low-cost electrocatalysts is critical for efficient hydrogen production by water electrolysis. Herein, we developed an advanced electrocatalyst by anchoring well-dispersed Ir nanoparticles on nickel metal-organic framework (MOF) Ni-NDC (NDC: 2,6-naphthalenedicarboxylic) nanosheets. Benefiting from the strong synergy between Ir and MOF through interfacial Ni-O-Ir bonds, the synthesized Ir@Ni-NDC showed exceptional electrocatalytic performance for hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and overall water splitting in a wide pH range, superior to commercial benchmarks and most reported electrocatalysts. Theoretical calculations revealed that the charge redistribution of Ni-O-Ir bridge induced the optimization of H2 O, OH* and H* adsorption, thus leading to the accelerated electrochemical kinetics for HER and OER. This work provides a new clue to exploit bifunctional electrocatalysts for pH-universal overall water splitting.

Electrosynthesis of α-Amino Acids from NO and other NOx species over CoFe alloy-decorated Self-standing Carbon Fiber Membranes.

The conversion of industrial exhaust gases of nitrogen oxides into high-value products is significantly meaningful for global environment and human health. And green synthesis of amino acids is vital for biomedical research and sustainable development of mankind. Herein, we demonstrate an innovative approach for converting nitric oxide (NO) to a series of α-amino acids (over 13 kinds) through electrosynthesis with α-keto acids over self-standing carbon fiber membrane with CoFe alloy. The essential leucine exhibits a high yield of 115.4 µmol h-1 corresponding a Faradaic efficiency of 32.4 %, and gram yield of products can be obtained within 24 hours in lab as well as an ultra-long stability (>240 h) of the membrane catalyst, which could convert NO into NH2 OH rapidly attacking α-keto acid and subsequent hydrogenation to form amino acid. In addition, this method is also suitable for other nitrogen sources including gaseous NO2 or liquidus NO3 - and NO2 - . Therefore, this work not only presents promising prospects for converting nitrogen oxides from exhaust gas and nitrate-laden waste water into high-value products, but also has significant implications for synthetizing amino acids in biomedical and catalytic science.

Electrocatalytic Synthesis of Pyridine Oximes using in Situ Generated NH2 OH from NO species on Nanofiber Membranes Derived from NH2 -MIL-53(Al).

Pyridine oximes produced from aldehyde or ketone with hydroxylamine (NH2 OH) have been widely applied in pharmaceutics, enzymatic and sterilization. However, the important raw material NH2 OH exhibits corrosive and unstable properties, leading to substantial energy consumption during storage and transportation. Herein, this work presents a novel method for directly synthesizing highly valuable pyridine oximes using in situ generated NH2 OH from electrocatalytic NO reduction with well-design nanofiber membranes (Al-NFM) derived from NH2 -MIL-53(Al). Particularly, 2-pyridinealdoxime, the precursor of antidote pralidoxime (2-PAM) for nerve agents suffering from scarcity and high cost, was achieved with a Faraday efficiency up to 49.8 % and a yield of 92.1 %, attributing to the high selectivity of NH2 OH production on Al-NFM, further easily reacted with iodomethane to produce 2-PAM. This study proposes a creative approach, having wide universality for synthesizing pyridine and other oximes with a range of functional groups, which not only facilitates the conversion of exhaust gas (NO) and waste water (NO2 - ) into valuable chemicals especially NH2 OH production and in situ utilization through electrochemistry, but also holds significant potential for synthesis of neuro detoxifying drugs to humanity security.

Electrocatalytic Synthesis of Essential Amino Acids from Nitric Oxide Using Atomically Dispersed Fe on N-doped Carbon.

How to transfer industrial exhaust gases of nitrogen oxides into high-values product is significantly important and challenging. Herein, we demonstrate an innovative method for artificial synthesis of essential α-amino acids from nitric oxide (NO) by reacting with α-keto acids through electrocatalytic process with atomically dispersed Fe supported on N-doped carbon matrix (AD-Fe/NC) as the catalyst. A yield of valine with 32.1 µmol mgcat -1 is delivered at -0.6 V vs. reversible hydrogen electrode, corresponding a selectivity of 11.3 %. In situ X-ray absorption fine structure and synchrotron radiation infrared spectroscopy analyses show that NO as nitrogen source converted to hydroxylamine that promptly nucleophilic attacked on the electrophilic carbon center of α-keto acid to form oxime and subsequent reductive hydrogenation occurred on the way to amino acid. Over 6 kinds of α-amino acids have been successfully synthesized and gaseous nitrogen source can be also replaced by liquid nitrogen source (NO3 - ). Our findings not only provide a creative method for converting nitrogen oxides into high-valued products, which is of epoch-making significance towards artificial synthesis of amino acids, but also benefit in deploying near-zero-emission technologies for global environmental and economic development.

Tailoring the Electronic Structure of an Atomically Dispersed Zinc Electrocatalyst: Coordination Environment Regulation for High Selectivity Oxygen Reduction.

Accurately regulating the selectivity of the oxygen reduction reaction (ORR) is crucial to renewable energy storage and utilization, but challenging. A flexible alteration of ORR pathways on atomically dispersed Zn sites towards high selectivity ORR can be achieved by tailoring the coordination environment of the catalytic centers. The atomically dispersed Zn catalysts with unique O- and C-coordination structure (ZnO3 C) or N-coordination structure (ZnN4 ) can be prepared by varying the functional groups of corresponding MOF precursors. The coordination environment of as-prepared atomically dispersed Zn catalysts was confirmed by X-ray absorption fine structure (XAFs). Notably, the ZnN4 catalyst processes a 4 e- ORR pathway to generate H2 O. However, controllably tailoring the coordination environment of atomically dispersed Zn sites, ZnO3 C catalyst processes a 2 e- ORR pathway to generate H2 O2 with a near zero overpotential and high selectivity in 0.1 M KOH. Calculations reveal that decreased electron density around Zn in ZnO3 C lowers the d-band center of Zn, thus changing the intermediate adsorption and contributing to the high selectivity towards 2 e- ORR.

Ultrafine Ru nanoparticles stabilized by V8C7/C for enhanced hydrogen evolution reaction at all pH.

The development of cost-effective electrocatalysts with high efficiency and long durability for hydrogen evolution reaction (HER) remains a great challenge in the field of water splitting. Herein, we design an ultrafine and highly dispersed Ru nanoparticles stabilized on porous V8C7/C matrix via pyrolysis of the metal-organic frameworks V-BDC (BDC: 1,4-benzenedicarboxylate). The obtained Ru-V8C7/C composite exhibits excellent HER performance in all pH ranges. At the overpotential of 40 mV, its mass activity is about 1.9, 4.1 and 9.4 times higher than that of commercial Pt/C in acidic, neutral and alkaline media, respectively. Meanwhile, Ru-V8C7/C shows the remarkably high stability in all pH ranges which, in particular, can maintain the current density of 10 mA cm-2 for over 150 h in 1.0 mol L-1 phosphate buffer saline (PBS). This outstanding HER performance can be attributed to the high intrinsic activity of Ru species and their strong interface interactions to the V8C7/C substrate. The synergistic effect of abundant active sites on the surface and the formed Ru-C-V units at the interface promotes the adsorption of reaction intermediates and the release of active sites, contributing the fast HER kinetics. This work provides a reference for developing versatile and robust HER catalysts by surface and interface regulation for pH tolerance.

Nickel metal-organic frameworks for visible-light CO2 reduction under mild reaction conditions.

Photochemical CO2 conversion into carbon fuel is a promising route to explore renewable energy and relieve climate change. However, it is still a key challenge to achieve high selectivity to CO and simultaneously achieve high conversion efficiency in photochemical CO2 reduction. Herein, we demonstrate the effect of Ni metal centers as catalytic active sites for the photocatalytic conversion of CO2 to CO by designing and constructing Ni metal-organic framework (Ni-MOF) materials. In pure CO2, Ni-MOF catalyst exhibits outstanding performance for visible-light-driven reductive CO2 deoxygenation with a high CO evolution rate of 19.13 µmol h-1 (per 1 mg of catalyst) and CO selectivity of 91.4%, which exceeds those of most reported systems. Upon using isostructural Co-MOF as the catalyst to replace Ni-MOF, a moderate performance towards CO2 photoreduction and low CO selectivity (40.1%) were observed, implying that the performance of CO2 photoreduction and CO selectivity are dependent on unsaturated metal centers.

Formation of brominated oligomers during phenol degradation on boron-doped diamond electrode.

In this research, the brominated oligomers formed during phenol degradation with boron-doped diamond (BDD) anode had been initially studied at three different concentrations of bromide (1, 10 and 100mM). The results from LC/MS analysis indicated that, brominated monomer, dimer and trimer of phenols resulting from electrophilic substitution and coupling reactions were the important reaction by-products. Specifically, the trimer by-products were generated only in bromide-rich systems. The reaction mechanisms concerning oligomer formations were proposed in detail accordingly. The above results were in well accordance with those recorded in the degradation experiments. As a whole, bromides and chlorides demonstrated quite different effects toward phenol degradation, which deepened our understanding on the reactions involved in BDD anode cells.

Chemometric study on the electrochemical incineration of diethylenetriaminepentaacetic acid using boron-doped diamond anode.

The electrochemical incineration of diethylenetriaminepentaacetic acid (DTPA) with boron-doped diamond (BDD) anode had been initially performed under galvanostatic conditions. The main and interaction effects of four operating parameters (flow rate, applied current density, sulfate concentration and initial DTPA concentration) on mineralization performance were investigated. Under similar experimental conditions, Doehlert matrix (DM) and central composite rotatable design (CCRD) were used as statistical multivariate methods in the optimization of the anodic oxidation processes. A comparison between DM model and CCRD model revealed that the former was more accurate, possibly due to its higher operating level numbers employed (7 levels for two variables). Despite this, these two models resulted in quite similar optimum operating conditions. The maximum TOC removal percentages at 180 min were 76.2% and 73.8% for case of DM and CCRD, respectively. In addition, with the aid of quantum chemistry calculation and LC/MS analysis, a plausible degradation sequence of DTPA on BDD anode was also proposed.

Degradation of creatinine using boron-doped diamond electrode: Statistical modeling and degradation mechanism.

This study investigated the degradation performance and mechanism of creatinine (a urine metabolite) with boron-doped diamond (BDD) anodes. Experiments were performed using a synthetic creatinine solution containing two supporting electrolytes (NaCl and Na2SO4). A three-level central composite design was adopted to optimize the degradation process, a mathematical model was thus constructed and used to explore the optimum operating conditions. A maximum mineralization percentage of 80% following with full creatinine removal had been achieved within 120 min of electrolysis, confirming the strong oxidation capability of BDD anodes. Moreover, the results obtained suggested that supporting electrolyte concentration should be listed as one of the most important parameters in BDD technology. Lastly, based on the results from quantum chemistry calculations and LC/MS analyses, two different reaction pathways which governed the electrocatalytic oxidation of creatinine irrespective of the supporting electrolytes were identified.