The mechanism of the oxygen evolution reaction (OER) by catalysts prepared electrodepositions from Co(2+) solutions in phosphate electrolytes (Co-Pi) was studied at neutral pH electrokinetic and (18)O isotope experiments. Low-potential enabled controlled preparation ultrathin Co-Pi catalyst films (<100 nm) that could be kinetically absence mass transport charge limitations to OER. exhibit a Tafel slope approximately equal 2.3 × RT/F for production water solutions. electrochemical rate law...

Thin catalyst films with electrocatalytic water oxidation properties similar to those of a recently reported Co-based can be electrodeposited from dilute Ni(2+) solutions in borate electrolyte at pH 9.2 (B(i)). The Ni-B(i) prepared precise thickness control and operate modest overpotential providing an alternative the Co for applications solar energy conversion.

A water oxidation catalyst generated via electrodeposition from aqueous solutions containing phosphate and Co2+ (Co−Pi) has been studied by in situ X-ray absorption spectroscopy. Spectra were obtained for Co−Pi films of two different thicknesses at an applied potential supporting catalysis open circuit. Extended fine structure (EXAFS) spectra indicate the presence bis-oxo/hydroxo-bridged Co subunits incorporated into higher nuclearity clusters Co−Pi. The average cluster is greater a...

An oxygen evolution catalyst that forms as a thin film from Ni(aq)(2+) solutions containing borate electrolyte (Ni-B(i)) has been studied by in situ X-ray absorption spectroscopy. A dramatic increase catalytic rate, induced anodic activation of the electrodeposited films, is accompanied structure and oxidation state changes. Coulometric measurements correlated with near-edge spectra active show nickel centers activated films possess an average +3.6, indicating substantial proportion exist...

Abstract Control over the architectural and electronic properties of heterogeneous catalysts poses a major obstacle in targeted design active stable non-platinum group metal electrocatalysts for oxygen reduction reaction. Here we introduce Ni 3 (HITP) 2 (HITP=2, 3, 6, 7, 10, 11-hexaiminotriphenylene) as an intrinsically conductive metal-organic framework which functions well-defined, tunable electrocatalyst alkaline solution. exhibits activity competitive with most stability during extended...

Electrolysis of Co2+ in phosphate, methylphosphonate, and borate electrolytes effects the electrodeposition an amorphous highly active water oxidation catalyst as a thin film on inert anode. Electrodeposition catalytically competent species immediately follows to Co3+ solution. Methylphosphonate support activity comparable that observed for phosphate. Catalytic O2 generation aqueous solutions containing 0.5 M NaCl is retained catalysts grown from phosphate electrolyte.

A cobalt-phosphate water-oxidizing catalyst forms from the oxidation of Co(2+) to Co(3+) in presence phosphate. We have employed radioactive (57)Co and (32)P isotopes probe dynamics this during water-oxidation catalysis. show that is self-healing phosphate crucial factor responsible for repair.

Thin-film water oxidation catalysts (Co−Pi) prepared by electrodeposition from phosphate electrolyte and Co(NO3)2 have been characterized electron paramagnetic resonance (EPR) spectroscopy. Co−Pi catalyst films exhibit EPR signals corresponding to populations of both Co(II) Co(IV). As the deposition voltage is increased into region where prevails, population Co(IV) rises decreases. The changes in redox speciation film can also be induced, part, prolonged catalysis absence additional...

Gold inverse opal (Au-IO) thin films are active for CO2 reduction to CO with high efficiency at modest overpotentials and selectivity relative hydrogen evolution. The specific activity evolution diminishes by 10-fold increasing porous film thickness, while is largely unchanged. We demonstrate that the origin of suppression in Au-IO stems from generation diffusional gradients within pores mesostructured electrode rather than changes surface faceting or Au grain size. For electrodes optimal...

A critical determinant of solar-driven water splitting efficiency is the kinetic profile O2 evolving catalyst (OEC). We now report profiles by a self-assembled nickel-borate (NiBi) OEC. Mechanistic studies anodized films NiBi exhibit low Tafel slope 2.3 × RT/2F (30 mV/decade at 25 °C). This together with an inverse third order rate dependence on H(+) activity establishes as ideal to be used in construction photoelectrochemical devices for splitting. In contrast, nonanodized display...

The development of nanomaterials for next generation photonic, optoelectronic, and catalytic applications requires a robust synthetic toolkit systematically tuning composition, phase, morphology at nanometer length scales. While de novo methods preparing from molecular precursors have advanced considerably in recent years, postsynthetic modifications these preformed nanostructures enabled the stepwise construction complex nanomaterials. Among transformations, cation exchange reactions, which...

A high surface area electrode is functionalized with cobalt-based oxygen evolving catalysts (Co-OEC = electrodeposited from pH 7 phosphate, Pi, 8.5 methylphosphonate, MePi, and 9.2 borate electrolyte, Bi). Co-OEC prepared MePi operated in Pi Bi achieves a current density of 100 mA cm−2 for water oxidation at 442 363 mV overpotential, respectively. The catalyst retains activity near-neutral buffered electrolyte natural waters such as those the Charles River (Cambridge, MA) seawater (Woods...

Abstract Iron- and nitrogen-doped carbon (Fe-N-C) materials are leading candidates to replace platinum catalysts for the oxygen reduction reaction (ORR) in fuel cells; however, their active site structures remain poorly understood. A postulate is that iron-containing sites exist primarily a pyridinic Fe-N 4 ligation environment, yet, molecular model generally feature pyrrolic coordination. Herein, we report hexaazacyclophane macrocycle, (phen 2 N )Fe, compare its spectroscopic,...

Significance Renewable electricity can be stored in the energy-dense bonds of carbon-based fuels via electroreduction CO 2 . reduction aqueous electrolytes suffers efficiency losses because simultaneous water to H Rational design selective -to-fuels catalysts requires direct knowledge electrode surface structure during turnover and how electrons protons couple product selectivity. Using model Au catalysts, we uncover complex heterogeneity binding equilibria differential proton coupling...

Transition-metal oxide and phosphate materials, commonly used for lithium battery devices, are active as oxygen evolution reaction (OER) catalysts under alkaline neutral solution conditions. Electrodes composed of LiCoO(2) LiCoPO(4) exhibit progressive deactivation activation OER catalysis, respectively, upon potential cycling at pH. The coincident with changes in surface morphology composition giving rise to spinel-like amorphous structures, respectively. structure the activated is...

Abstract An electrode's performance for catalytic CO 2 conversion to fuels is a complex convolution of surface structure and transport effects. Using well‐defined mesostructured silver inverse opal (Ag‐IO) electrodes, it demonstrated that mesostructure‐induced limitations alone serve increase the turnover frequency activation per unit area, while simultaneously improving reaction selectivity. The specific activity catalyzed evolution systematically rises by three‐fold H declines ten‐fold...

Rational design of selective CO2-to-fuels electrocatalysts requires direct knowledge the electrode surface structure during turnover. Metallic Cu is most versatile catalyst, capable generating a wide array value-added products, including methane, ethylene, and ethanol. All these products are postulated to form via common surface-bound CO intermediate. Therefore, kinetics thermodynamics adsorption play central role in determining fuel-formation selectivity efficiency, highlighting need for...

Herein, we show that group 11 CO2 reduction catalysts are rapidly poisoned by progressive deposition of trace metal ion impurities present in high purity electrolytes. Metal impurity was characterized XPS and situ stripping voltammetry is coincident with loss catalytic activity selectivity for reduction, favoring hydrogen evolution on surfaces. can be suppressed complexing ethylenediaminetetraacetic acid or solid-supported iminodiacetate resins. complexation allows reproducible, sustained...

The mechanism of nucleation, steady-state growth, and repair is investigated for an oxygen evolving catalyst prepared by electrodeposition from Co(2+) solutions in weakly basic electrolytes (Co-OEC). Potential step chronoamperometry atomic force microscopy reveal that nucleation Co-OEC progressive reaches a saturation surface coverage ca. 70% on highly oriented pyrolytic graphite substrates. Steady-state exhibits Tafel slope approximately equal to 2.3 × RT/F. electrochemical rate law first...

We show that bicarbonate is neither a general acid nor reaction partner in the rate-limiting step of electrochemical CO2 reduction catalysis mediated by planar polycrystalline Au surfaces. formulate microkinetic models and propose diagnostic criteria to distinguish role bicarbonate. Comparing these with observed zero-order dependence simulated interfacial concentration gradients, we conclude not cocatalyst. Instead, it acts as viable proton donor past sluggish buffer maintains bulk but local...

Condensation of fac-Re(5,6-diamino-1,10-phenanthroline)(CO)3Cl to o-quinone edge defects on graphitic carbon surfaces generates graphite-conjugated rhenium (GCC-Re) catalysts that are highly active for CO2 reduction CO in acetonitrile electrolyte. X-ray photoelectron and absorption spectroscopies establish the formation surface-bound Re centers with well-defined coordination environments. GCC-Re species glassy display catalytic currents greater than 50 mA cm−2 96 ± 3% Faradaic efficiency...

Correlating the current/voltage response of an electrode to intrinsic properties active material requires knowledge electrochemically surface area (ECSA), a parameter that is often unknown and overlooked, particularly for highly nanostructured electrodes. Here we demonstrate power nonaqueous electrochemical double layer capacitance (DLC) provide reasonable estimates ECSA across 17 diverse materials spanning metals, conductive oxides, chalcogenides. Whereas data recorded in aqueous...