Front Cover Image: Volume 3 Issue 2

Evaluation of nickel-molybdenum-oxides as cathodes for hydrogen evolution by water electrolysis in acidic, alkaline, and neutral media

Carbon dioxide (CO2) reduction is important for enviormental protection, reducing climate warming trends and energy conversion and storage. Photocatalytic CO2 reduction reaction (CO2RR) in visible light is a highly important green route for this target. The variation of active sites on vairous semiconductor have been extensively studied. Exploring new routes for CO2RR is highly desired. Herein, we successfully loaded single tungsten atomic oxide (STAO) on BiOBr substrate. A visible-light-driven photocatalytic CO2RR is achieved by STAO/BiOBr, and the stability has been realized. The CO production of STAO/BiOBr was more than one time larger than that of bare BiOBr and CH4 is also realized. The photo-electric performance of STAO/BiOBr is much different with that of bare BiOBr. By investigating the active sites on single site anchored BiOBr base, the single sites of tungsten played as reductive active sites for CO2 to replace Bi atoms on bare BiOBr. This study sheds lights for photocatalytic CO2RR by single atomic sites through single metallic atom oxides.

Anion exchange membrane water electrolysis (AEMWE) is a promising technology to produce hydrogen from low-cost, renewable power sources. Recently, the efficiency and durability of AEMWE have improved significantly due to advances in the anion exchange polymers and catalysts. To achieve performances and lifetimes competitive with proton exchange membrane or liquid alkaline electrolyzers, however, improvements in the integration of materials into the membrane electrode assembly (MEA) are needed. In particular, the integration of the oxygen evolution reaction (OER) catalyst, ionomer, and transport layer in the anode catalyst layer has significant impacts on catalyst utilization and voltage losses due to the transport of gases, hydroxide ions, and electrons within the anode. This study investigates the effects of the properties of the OER catalyst and the catalyst layer morphology on performance. Using cross-sectional electron microscopy and in-plane conductivity measurements for four PGM-free catalysts, we determine the catalyst layer thickness, uniformity, and electronic conductivity and further use a transmission line model to relate these properties to the catalyst layer resistance and utilization. We find that increased loading is beneficial for catalysts with high electronic conductivity and uniform catalyst layers, resulting in up to 55% increase in current density at 2 V due to decreased kinetic and catalyst layer resistance losses, while for catalysts with lower conductivity and/or less uniform catalyst layers, there is minimal impact. This work provides important insights into the role of catalyst layer properties beyond intrinsic catalyst activity in AEMWE performance.

Hemin functionalized graphene nanosheets-based dual biosensor platforms for hydrogen peroxide and glucose

Phosphorus-doping induced electronic modulation of CoS2–MoS2 hollow spheres on MoO2 film-Mo foil for synergistically boosting alkaline hydrogen evolution reaction

Electrocatalyst nanoarchitectonics with molybdenum-cobalt bimetallic alloy encapsulated in nitrogen-doped carbon for water splitting reaction

Currently, the most efficient electrocatalyst for the hydrogen evolution reaction (HER) in water dissociation is Pt‐based catalyst. Unfortunately, the high cost and less than perfect efficiency hinder wide‐range industrial/technological applications. Here, by controlling the treatment temperature of tris (2,2‐bipyridine) ruthenium dichloride hexahydrate, synthesis of compounds with novel ruthenium single/dual atoms (Ru S/DAs) mixed with Ru nanoclusters (Ru S/DAs + Ru NCs) and supported by carbon dots is demonstrated. These compounds are shown to be highly efficient and competitive catalysts for hydrogen evolution. Ru S/DAs + Ru NCs exhibit very high activity, with overpotentials of 15 and 40 mV at a current density of 10 mA/cm2 in 1.0 mol/L KOH and 0.5 mol/L H2SO4, respectively. Furthermore, the composites are found to possess outstanding stability and rapid HER kinetics. X ray absorption fine structure analysis, supported by density functional theory calculations, shows charge rearrangement in single‐atomic Ru, and the Ru dual sites promote active hydrogen adsorption and recombination. Ru S/DAs and Ru NCs demonstrate high electroactivity due to the electroactive Ru 4d orbitals. The introduction of Ru NCs activates the carbon support, providing a high electronic conductivity to transfer electrons from Ru NCs to Ru S/DAs, and facilitates water dissociation for the HER process.

Hydrogen production through water electrolysis calls for a low-cost non-fluoro membrane to make the process economically viable due to the high cost and environmental concerns of the current fluorinated ionomers. Here, we present such an ionomer with high proton conductivity based on the hybrid of commercially available poly(styrene-co-maleic anhydride) and polyhedral oligomeric silsesquioxane (POSS). The three-dimensional POSS framework, which does not only act as a robust scaffold but also provides binding sites for water, contributes to the amount of bound water, high proton conductivity and good oxidative stability.

Incorporation of single cobalt active sites onto N-doped graphene for superior conductive membranes in electrochemical filtration

Materials exhibiting high ionic mobilities in the solid state at room temperature have mainly been found in the silver ion conductors which are based on silver iodide. Though silver iodide is a low conductivity solid at room temperature, it exhibits high ionic conductivity at relatively higher temperatures. In order to stabilize this high conductivity phase of silver iodide at room temperature, the introduction of foreign cations or anions into the lattice of silver iodide has been attempted. In this paper, the various silver ion high conductivity solids are reviewed, together with those showing both high ionic and electronic conductivity.

ABSTRACTThe trade-off between the intrinsic activity and electronic conductivity of carbon materials is a major barrier for electrocatalysis. We report a Janus-type carbon material combining electrically conductive nitrogen-doped carbon (NC) and catalytically active boron, nitrogen co-doped carbon (BNC). The integration of NC with BNC can not only ensure high electronic conductivity of the hybrid, but also achieve an enhancement in the intrinsic activity of the BNC side due to the electron redistribution on their coupling interfaces. In the electrocatalytic hydrazine oxidation reaction (HzOR), the Janus carbon electrocatalyst exhibits superior activity than their single counterparts and simple physical mixtures. Density functional theory calculations reveal that the NC/BNC interfaces simultaneously promote efficient electron transport and decrease the free energy of the rate-determining step in the HzOR process.

Boosting diesel soot catalytic combustion via enhancement of solid(catalyst)-solid(soot) contact by tailoring micrometer scaled sheet-type agglomerations of CeO2-ZrO2 catalyst

Conductive Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been extensively used as non-metallic electrodes. However, the relatively low electrical conductivity of pristine PEDOT:PSS film restricts its further application. Although doping high content conductive filler or increasing the film thickness are effective for enhancing the electrical property, the transparency is sacrificed, which limits the application of PEDOT:PSS films. In this study, preparing PEDOT:PSS composite film with highly conductive and transparent property was the primary purpose. To achieve this goal, single-walled carbon nanotubes (SWCNTs) and dimethyl sulfoxide (DMSO) was chosen to composite with PEDOT:PSS. The spin-coated SWCNT/PEDOT:PSS composite film exhibited excellent electrical conductivity and transparency. The electrical conductivity of composite film with desired transmittance property (78%) reached the highest value (1060.96 S cm−1) at the SWCNTs content was 6 wt%. Under the modification process applied in this work, the non-conductive PSS was partially removed by incorporated DMSO and SWCNTs. Then, the molecular chains of PEDOT stretched and adsorbed onto the surface of SWCNTs, forming a highly efficient three-dimensional conductive structure, which contributed to the enhancement of electrical conductivity and transparency. Additionally, the spin-coating process allowed for the reduction of film thickness, ensuring better transparency. This research contributed to expanding the further applications of PEDOT:PSS films in high-performance transparent film electrodes.

Single atomic site catalyst/organic polymers hybrid photocatalyst has been demonstrated as a potential material for photocatalytic CO2 reduction that can solve both environmental and energy issues simultaneously. The charge migration and transfer between organic polymers and single atomic site catalysts are attributed to the high performance of the hybrid material. In this review, two typical charge transfers between the single atomic site catalyst and organic polymer‐based semiconductor, namely intermolecular electron transfer and intramolecular electron transfer, are discussed. Typical single‐atomic site catalysts, organic polymers, and methods are first reviewed for the fabrication of hybrid systems. Why intramolecular electron transfer between the single atomic site catalyst and organic polymers exhibits higher photocatalytic activity than intermolecular electron transfer is also discussed. Finally, the critical challenges in fabricating these hybrid photocatalysts toward an efficient photocatalytic CO2 reduction are highlighted, and propose solutions to these challenges.

Regulating site‐to‐site interactions between active sites can effectively tailor the electrocatalytic behavior of single‐atom catalysts (SACs). The conventional SACs suffer from low density of single atoms and lack of site‐to‐site interactions between them. Herein, a series of interactive Pt SACs with controllable Pt–Pt spatial correlation degree and local coordination environment is developed by integrating densely populated Pt single atoms in the sub‐lattice of a Co 3 O 4 matrix. The obtained interactive Pt‐Co 3 O 4 catalysts demonstrate remarkable electrocatalytic performance toward hydrogen production, outperforming those of isolated single atom‐ and nanoparticle‐based catalysts. The intrinsic catalytic activity of interactive Pt‐Co 3 O 4 catalysts is closely dependent on the spatial structure of Pt sites with the adjusted d ‐band center by regulating contents and atomic configuration of Pt sites. This work provides fundamental insights for the structure‐property relationship on interactive single active sites, which is expected to direct the rational design of highly efficient SACs.