Combining theory and experiment in electrocatalysis: Insights into materials design

Better living through water-splitting Chemists have known how to use electricity to split water into hydrogen and oxygen for more than 200 years. Nonetheless, because the electrochemical route is inefficient, most of the hydrogen made nowadays comes from natural gas. Seh et al. review recent progress in electrocatalyst development to accelerate water-splitting, the reverse reactions that underlie fuel cells, and related oxygen, nitrogen, and carbon dioxide reductions. A unified theoretical framework highlights the need for catalyst design strategies that selectively stabilize distinct reaction intermediates relative to each other. Science , this issue p. 10.1126/science.aad4998 </jats:p

Effects of Gold Substrates on the Intrinsic and Extrinsic Activity of High-Loading Nickel-Based Oxyhydroxide Oxygen Evolution Catalysts

We systematically investigate the effects of Au substrates on the oxygen evolution activities of cathodically electrodeposited nickel oxyhydroxide (NiOOH), nickel–iron oxyhydroxide (NiFeOOH), and nickel–cerium oxyhydroxide (NiCeOOH) at varying loadings from 0 to 2000 nmol of metal/cm2. We determine that the geometric current densities, especially at higher loadings, were greatly enhanced on Au substrates: NiCeOOH/Au reached 10 mA/cm2 at 259 mV overpotential, and NiFeOOH/Au achieved 140 mA/cm2 at 300 mV overpotential, which were much greater than those of the analogous catalysts on graphitic carbon (GC) substrates. By performing a loading quantification using both inductively coupled plasma optical emission spectrometry and integration of the Ni2+/3+ redox peak, we show that the enhanced activity is predominantly caused by the stronger physical adhesion of catalysts on Au. Further characterizations using impedance spectroscopy and in situ X-ray absorption spectroscopy revealed that the catalysts on Au exhibited lower film resistances and higher number of electrochemically active metal sites.We attribute this enhanced activity to a more homogeneous electrodeposition on Au, yielding catalyst films with very high geometric current densities on flat substrates. By investigating the mass and site specific activities as a function of loading, we bridge the practical geometric activity to the fundamental intrinsic activity

The Processing of Grammar Violations in Minimal Phrase Structures: An ERP Study

There is still a gap in our knowledge about how the brain composes form and meaning in language, but we do know that the ability to compose individual syntactic units into complex utterances is uniquely human. Manipulating syntactic units in simple phrases may help us understand composition in language more clearly. This study is concerned with how syntactic modulation impact composition of minimal phrases. Adjective-noun phrases are investigated using EEG. We studied online event related potentials (ERPs) and offline behavioural responses for 30 Norwegian Bokmål language users using compositional phrases such as “en autentisk maler” (“an authentic painter”) and “en falsk lærer” (“a fake teacher”), and grammar violation phrases such as “en australsk band” (“a Australian band”) and “en cirka professor” (“a circa professor”). This study focuses on one composition comparison composed of three semantic conditions, and two grammar violations: a submodifier violation in a [Det Adv N] construction where the adverb requires an adjective to create meaning, and an agreement violation with the [Det Adj N] construction where the determiner does not follow the inflection of the noun. The ERPs were derived from the critical noun. A P600 effect were found for both the composition comparisons and the grammar violation comparisons against the baselines. Unexpectedly, we found the P600 effect to be processed similarly for all the conditions mentioned. The results in compositional phrases with and without grammar violations indicate that the P600 might reflect the interplay between syntax and semantics. Additionally, the P600 effect in the submodifier violation condition indicates that participants processed the adverb as a word in which the noun could derive meaning, whether this was derived successfully or not

Local surface structure and composition control the hydrogen evolution reaction on iron nickel sulfides

In order to design more powerful electrocatalysts, developing our understanding of the role of the surface structure and composition of widely abundant bulk materials is crucial. This is particularly true in the search for alternative hydrogen evolution reaction (HER) catalysts to replace platinum. We report scanning electrochemical cell microscopy (SECCM) measurements of the (111)‐crystal planes of Fe4.5Ni4.5S8, a highly active HER catalyst. In combination with structural characterization methods, we show that this technique can reveal differences in activity arising from even the slightest compositional changes. By probing electrochemical properties at the nanoscale, in conjunction with complementary structural information, novel design principles are revealed for application to rational material synthesis

Atomic-layer-deposited ultrafine MoS2 nanocrystals on cobalt foam for efficient and stable electrochemical oxygen evolution

Ultrafine molybdenum sulfide (MoS2) nanocrystals are grown on a porous cobalt (Co) foam current collector by atomic layer deposition (ALD) using molybdenum hexacarbonyl and hydrogen sulfide as precursors. When used to catalyze the oxygen evolution reaction (OER), the optimal Co@MoS2 electrode, even with a MoS2 loading as small as 0.06 mg cm-2, exhibits a large cathodic shift of ca. 200 mV in the onset potential (the potential at which the current density is 5 mA cm-2), a low overpotential of only 270 mV to attain an anodic current density of 10 mA cm-2, much smaller charge transfer resistance and substantially improved long-term stability at both low and high current densities, with respect to the bare Co foam electrode, showing substantial promise for use as an efficient, low-cost and durable anode in water electrolyzers.L. F. Liu acknowledges the support of the FCT Investigator grant (no. IF/01595/2014) and the Exploratory grant (No. IF/01595/2014/CP1247/CT0001) from the Portuguese Foundation of Science & Technology (FCT). D. H. Xiong and W. Li are thankful for the financial support from Marie Curie Action COFUND fellowships (NanoTrainforGrowth, Grant Agreement no. 600375) under the FP7 framework. D. H. Xiong also acknowledges the financial support from the China Postdoctoral Science Foundation (No. 2015 T80847). This work was partly funded by the European Commission Horizon 2020 project "CritCat" (Grant Agreement No. 686053).info:eu-repo/semantics/publishedVersio