A bio-inspired coordination polymer as outstanding water oxidation catalyst via second coordination sphere engineering.

TL;DR: In this paper, the authors present fundamentals of heterogeneous electrocatalysis and some primary reactions, and then implement these to establish the framework of e-refinery by coupling in situ generated intermediates (integrated reactions) or products (tandem reactions).

TL;DR: In this article, the authors provide some basic principles of water electrolysis, key aspects of oxygen evolution reaction (OER), and significant criteria for the development of the catalysts.

TL;DR: In this article, the current progress on metal-organic frameworks (MOFs) and their derivatives for OER electrolysis is summarized, highlighting the design principle, synthetic methods and performance for MOF-based materials.

TL;DR: In this article, a nanocrystalline CeO2 in a Co3O4/CeO2 nanocomposite was shown to modify the redox properties of Co3 O4 and enhance its intrinsic oxygen evolution reaction activity.

Abstract: DOI: 10.1002/aenm.201602547 due to their different redox behaviors and/or diverse solubility product constants of these metal ions with hydroxide ions. Herein, we report a stepwise electrodeposition strategy to make an ultrathin NiFe film, whose catalytic activity for water oxidation is significantly improved as compared to the NiFe film formed by a typical cathodic electrolysis method. By using the stepwise strategy, that is first deposition of Ni-based film via cathodic electrolysis followed by the integration of Fe species via anodic CV (Figure 1), the amounts of Ni/Fe-based materials loaded on electrodes can be controlled. In addition, the interconnected reticular film structure resulted from stepwise deposition is favorable to electrocatalytic water oxidation by assisting both mass and charge transportation. This work should therefore be very valuable to film preparation that is interesting in electrocatalysis and other electrochemical studies. Typically, a layer of Ni-based film was first deposited on an electrode by cathodic electrolysis of an Ni(NO3)2 aqueous solution at an applied potential of −0.80 V versus normal hydrogen electrode (NHE) for 300 s. The electrode was then rinsed and immersed in a freshly prepared FeSO4 acetate buffer (0.1 m, pH 7.0) under argon for CV incorporation of Fe into the previously formed Ni-based film. The CV deposition was conducted in one cycle of 0.20–1.35 V versus NHE. It is worth noting that prior to the dissolution of FeSO4, the acetate buffer is vigorously bubbled with argon for at least 30 min to remove the dissolved O2 in the solution. Argon protection is essential to prevent the oxidation of FeII to FeIII by O2, a step aimed at well-controlled Fe deposition.[21,22] This NiFe film from stepwise electrodeposition is denoted hereafter as NiFe-SW. The film evolution is illustrated in Figure 1 showing the optical images of the film on indium tin oxide (ITO) electrodes and scanning electron microscopy (SEM) images of the film on glassy carbon (GC) electrodes. The transparent nature of this ultrathin film permits its potential uses in photoactive devices.[21,31,32] The morphologies of electrodeposited films were analyzed by SEM and transmission electron microscopy (TEM). As shown in Figure 2A, Ni-based film from cathodic electrolysis was composed of isolated nanoplates with legible boundaries. Such isolated domains have been commonly observed for films that are electrodeposited using the electrolysis method.[18,23,26] After CV incorporation of Fe into the aforementioned Ni-based film, the resulting NiFe-SW film consisted of uniformly interconnected nanoribbons with porous structures (Figure 2B–D). TEM image of Ni-based film showed nanoplates with a layered morphology and edge steps, which was consistent with typical metal hydroxide structures (Figure 2E).[45] On the contrary, NiFe-SW film evolved into curly and contorted nanosheets Increasing energy demands and environmental issues related to the use of fossil fuels have forced people to exploit sustainable and carbon-free energy resources.[1–5] Artificial photosynthesis, actualized via water splitting, is a mimic of the natural system for solar-to-chemical energy conversion, and is a subject attracting overwhelming solicitudes.[6–12] However, water oxidation, as one of the half reactions of water splitting, is kinetically very slow and limits the overall efficiency of water splitting.[3,8,13,14] Therefore, developing efficient catalysts for water oxidation has become the heart of renewableenergy technologies, and has attracted tremendous research interests.[3,8,13–17] Oxides, hydroxides, and oxyhydroxides of the first-row transition metals (Mn,[18–20] Fe,[21,22] Co,[23–25] Ni,[26–30] Cu[31,32]), containing either single or multiple metal elements,[33–48] are active for electrocatalytic water oxidation. Electrodeposition has been shown to be a valuable method to make these catalyst films on electrodes,[18,23,26,28,39,41,46,49] a process typically realized via cathodic/anodic electrolysis using solutions containing a single metal ion,[18,23,26] mixed metal ions,[39,41,46,49] or a metal complex precursor.[28] Recently, we demonstrated that cyclic voltammetry (CV) deposition is a fast and simple method to prepare Fe-based films for water oxidation.[21,22] Importantly, it is challenging to prepare Fe-based catalyst films with similar water oxidation activities by using the traditional electrolysis method. Inspired by this CV deposition, we are interested in re-examining the fabrication of NiFe films and their catalytic features. The reason to choose the NiFe system is twofold. First, NiFe materials with low cost and low toxicity have been shown to be highly active for catalytic water oxidation.[34,35,39–43,45] Second, electrodeposited NiFe films are generally prepared by cathodic electrolysis of a solution containing both NiII and FeII/FeIII ions,[39,41,46] a process that is difficult to be precisely controlled

TL;DR: The proton inventory technique uses the dependence of enzymic reaction rate on the atom fraction of deuterium present in mixtures of protium oxide and deuterIUM oxide to deduce for simple cases the number of exchangeable hydrogenic sites that produce isotope effects, and the magnitude of the isotope effect generated at each site.

TL;DR: Well-ordered NiFe-MOF-74 is in situ grown on Ni foam by the induction of Fe2+ and directly used as an OER electrocatalyst with outstanding water oxidation activity in alkaline electrolytes with an overpotential of 223 mV at 10 mA cm-2.

TL;DR: The results highlight the significant impact of surface protonation on O-O bond formation pathways and oxygen evolution kinetics on hematite surfaces and the reaction intermediates by operando Fourier-transform infrared spectroscopy.