Topotactically constructed nickel-iron(oxy)hydroxide with abundant in-situ produced high-valent iron species for efficient water oxidation

The low efficiency of oxygen evolution reaction(OER) is regarded as one of the major roadblocks for metal-air batteries and water electrolysis.Herein,a high-performance OER catalyst of NiFe_(0.2)(oxy)hydroxide(NiFe_(0.2)-O_(x)H_(y)) was developed through topotactic transformation of a Prussian blue analogue in an alkaline solution,which exhibits a low overpotential of only 263 mV to reach a current density of 10 mA cm^(-2) and a small Tafel slope of 35 mV dec-1.Ex-situ/operando Raman spectroscopy results indicated that the phase structure of NiFe_(0.2)-O_(x)H_(y) was irreversibly transformed from the type of α-Ni(OH)_(2) to γ-NiOOH with applying an anodic potential,while ex-situ/operando 57Fe Mossbauer spectroscopic studies evidenced the in-situ production of abundant high-valent iron species under OER conditions,which effectively promoted the OER catalysis.Our work elucidates that the amount of high-valent iron species in-situ produced in the NiFe(oxy)hydroxide has a positive correlation with its water oxidation reaction performance,which further deepens the understanding of the mechanism of NiFe-based electrocatalysts.

Identification of relevant active sites and a mechanism study for reverse water gas shift reaction over Pt/CeO_2 catalysts

Reverse water gas shift (RWGS) reaction can serve as a pivotal stage in the CO2 conversion processes, which is vital for the utilization of CO2. In this study, RWGS reaction was performed over Pt/CeO2 catalysts at the temperature range of 200-500 degrees C under ambient pressure. Compared with pure CeO2, Pt/CeO2 catalysts exhibited superior RWGS activity at lower reaction temperature. Meanwhile, the calculated TOF and E-a values are approximately the same over these Pt/CeO2 catalysts pretreated under various calcination conditions, indicating that the RWGS reaction is not affected by the morphologies of anchored Pt nanoparticles or the primary crystallinity of CeO2. TPR and XPS results indicated that the incorporation of Pt promoted the reducibility of CeO2 support and remarkably increased the content of Ce 3 + sites on the catalyst surface. Furthermore, the CO TPSR-MS signal under the condition of pure CO2 flow over Pt/CeO 2 catalyst is far lower than that under the condition of adsorbed CO2 with H-2 -assisted flow, revealing that CO2 molecules adsorbed on Ce3+ active sites have difficult in generating CO directly. Meanwhile, the adsorbed CO2 with the assistance of H-2 can form formate species easily over Ce3+ active sites and then decompose into Ce3+-CO species for CO production, which was identified by in-situ FTIR. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B. V. and Science Press. All rights reserved.

The development and application of dual-comb spectroscopy in analytical chemistry

Analytical chemistry plays an important role in the qualitive and quantitative analysis for molecules in the various circumstances,especially for the high-resolution analysis.The dual-comb spectroscopy(DCS)technology with the characteristics of high resolution,high sensitivity and instantaneous sampling exhibited a great potential in high-resolution in-situ spectral methods and has been active in the fields of spatial ranging,air composition analysis,reaction monitoring and so on.In this review,we will summarize the principle of DCS according to the different wavelength coverage and overview the applications of DCS in analytical chemistry.

Electron-withdrawing functional ligand promotes CO2 reduction catalysis in single atom catalyst

Electrochemical carbon dioxide reduction reaction (CO2RR) powered by renewable electricity offers an attractive approach to reduce carbon emission and at the same time produce valuable chemicals/fuels.To design efficient CO2 reduction electrocatalyst,it is important to understand the structure-activity relationship.Herein,we design a series of single Co atoms electrocatalysts with well-defined active sites electronic structures,which exhibit outstanding CO2RR activity with controllable selectivity to CO.Experimental and density functional theory (DFT) calculation studies show that introducing nitro (amino) ligand next to single Co atom catalytic center with electron-withdrawing (electron-donating) capability favors (hinders) CO2 reduction catalysis.This work provides an in-depth understanding of how functional ligand affects the splitting of transition metal 3d electron orbital,thereby changing the electron transfer from transition metal active site to CO2,which is closely related to the Gibbs free energy of the rate-determining step (CO2+e^-+*→*CO2^-).