The development of oxygen evolution reaction (OER) electrocatalysts remains a major challenge that requires significant advances in both mechanistic understanding and material design. Recent studies show that oxygen from the perovskite oxide lattice could participate in the OER via a lattice oxygen-mediated mechanism, providing possibilities for the development of alternative electrocatalysts that could overcome the scaling relations-induced limitations found in conventional catalysts utilizing the adsorbate evolution mechanism. Here we distinguish the extent to which the participation of lattice oxygen can contribute to the OER through the rational design of a model system of silicon-incorporated strontium cobaltite perovskite electrocatalysts with similar surface transition metal properties yet different oxygen diffusion rates. The as-derived silicon-incorporated perovskite exhibits a 12.8-fold increase in oxygen diffusivity, which matches well with the 10-fold improvement of intrinsic OER activity, suggesting that the observed activity increase is dominantly a result of the enhanced lattice oxygen participation.

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This study aims to develop a novel approach for the production of analytically robust and miniaturized polymeric ion sensors that are vitally important in modern analytical chemistry (e.g., clinical chemistry using single blood droplets, modern biosensors measuring clouds of ions released from nanoparticle tagged biomolecules, lab-on-a-chip applications, etc.). This research has shown that the use of a water repellent polymethyl methacrylate/polydecyl methacrylate (PMMA/PDMA) copolymer as the ion sensing membrane, along with a hydrophobic poly(3-octylthiophene 2,5-diyl) (POT) solid-contact as the ion-to-electron transducer, is an excellent strategy for avoiding the detrimental water layer formed at the buried interface of solid-contact ISEs. Accordingly, it has been necessary to implement a rigorous surface analysis scheme employing electrochemical impedance spectroscopy (EIS), in-situ neutron reflectometry/EIS (NR/EIS), secondary ion mass spectrometry (SIMS) and small angle neutron scattering (SANS) to probe structurally the solid-contact/membrane interface, so as to identify the conditions that eliminate the undesirable water layer in all solid-state polymeric ion sensors. In this work, we provide the first experimental evidence that the PMMA/PDMA copolymer system is susceptible to water “pooling” at the interface in areas surrounding physical imperfections in the solid-contact, with the exposure time for such an event in a PMMA/PDMA copolymer ISE taking nearly twenty times longer than that for a plasticized polyvinyl chloride (PVC) ISE, and the simultaneous use of a hydrophobic POT solid-contact with a PMMA/PDMA membrane can eliminate totally this water layer problem.

This paper presents the very first direct structural evidence for the formation of a 100 +/- 10 A water layer in coated-wire polymeric-membrane ion-selective electrodes (ISEs).

Iron single atom catalysts (Fe SACs) are the best‐known nonprecious metal (NPM) catalysts for the oxygen reduction reaction (ORR) of polymer electrolyte membrane fuel cells (PEMFCs), but their practical application has been constrained by the low Fe SACs loading (<2 wt%). Here, a one‐pot pyrolysis method is reported for the synthesis of iron single atoms on graphene (FeSA‐G) with a high Fe SAC loading of ≈7.7 ± 1.3 wt%. The as‐synthesized FeSA‐G shows an onset potential of 0.950 V and a half‐wave potential of 0.804 V in acid electrolyte for the ORR, similar to that of Pt/C catalysts but with a much higher stability and higher phosphate anion tolerance. High temperature SiO 2 nanoparticle‐doped phosphoric acid/polybenzimidazole (PA/PBI/SiO 2 ) composite membrane cells utilizing a FeSA‐G cathode with Fe SAC loading of 0.3 mg cm −2 delivers a peak power density of 325 mW cm −2 at 230 °C, better than 313 mW cm −2 obtained on the cell with a Pt/C cathode at a Pt loading of 1 mg cm −2 . The cell with FeSA‐G cathode exhibits superior stability at 230 °C, as compared to that with Pt/C cathode. Our results provide a new approach to developing practical NPM catalysts to replace Pt‐based catalysts for fuel cells.

The practical application of single atom catalysts (SACs) is constrained by the low achievable loading of single metal atoms. Here, nickel SACs stabilized on a nitrogen-doped carbon nanotube structure (NiSA-N-CNT) with ultrahigh Ni atomic loading up to 20.3 wt % have been successfully synthesized using a new one-pot pyrolysis method employing Ni acetylacetonate (Ni(acac) 2 ) and dicyandiamide (DCD) as precursors. The yield and formation of NiSA-N-CNT depends strongly on the Ni(acac) 2 /DCD ratio and annealing temperature. Pyrolysis at 350 and 650 °C led to the formation of Ni single atom dispersed melem and graphitic carbon nitride (Ni-melem and Ni-g-C 3 N 4 ). Transition from a stacked and layered Ni-g-C 3 N 4 structure to a bamboo-shaped tubular NiSA-N-CNT structure most likely occurs via a solid-to-solid curling or rolling-up mechanism, thermally activated at temperatures of 700−900 °C. Extended X-ray absorption fine structure (EXAFS) experiments and simulations show that Ni single atoms are stabilized in the N-CNT structure through nitrogen coordination, forming a structure with four nearest N coordination shell surrounded by two carbon shells, Ni−N 4 . The NiSA-N-CNT catalysts show an excellent activity and selectivity for the electrochemical reduction of CO 2 , achieving a turnover frequency continued...

The use of perovskite materials as anion-based intercalation pseudocapacitor electrodes has received significant attention in recent years. Notably, these materials, characterized by high oxygen vacancy concentrations, do not require high surface areas to achieve a high energy storage capacity as a result of the bulk intercalation mechanism. Here we report that reduced PrBaMn 2 O 6- (r-PBM), possessing a layered double perovskite structure, exhibits ultrahigh capacitance and functions as an excellent oxygen anion-intercalation-type electrode material for supercapacitors.Formation of the layered double perovskite structure, as facilitated by hydrogen treatment, is shown to significantly enhance the capacitance, with the resulting r-PBM material demonstrating a very high gravimetric capacitance of 1034.8 F g -1 and an excellent volumetric capacitance of approximately 2535.3 F cm -3 at a current density of 1 A g -1 . The resultant formation of a double perovskite crystal oxide with a specific layered structure leads to the r-PBM with a substantially higher oxygen diffusion rate and oxygen vacancy concentration. These superior characteristics show immense promise for their application as oxygen anion-intercalation-type electrodes in pseudocapacitors.

Electrically insulating objects gain a net electrical charge when brought in and out of contact. This phenomenon -triboelectricity -involves the flow of charged species, but to conclusively establish their nature has proven extremely difficult. Here, we demonstrate an almost linear relationship between a plastic sample's net negative charge and the amount of solution metal ions discharged to metallic particles, with a coefficient of proportionality linked to its electron affinity (stability of anionic fragments). The maximum magnitude of reductive redox work is also material-dependent: metallic particles grow to a larger extent over charged dielectrics that yield stable cationic fragments (smaller ionization energy). Importantly, the extent to which the sample can act as electron source greatly exceeds the net charging measured in a Faraday pail/electrometer set up, which brings direct evidence of triboeletricity being a mosaic of positive and negative charges rather than a homogenous ensemble, and defines for the first time their quantitative scope in electrochemistry.