Recent advances in hydrogen storage technologies based on nanoporous carbon materials

AbstractHydrogen is a promising energy carrier that can potentially facilitate a transition from fossil fuels to sustainable energy sources without producing harmful by-products. Prior to realizing a hydrogen economy, however, viable hydrogen storage materials must be developed. Physical adsorption in porous solids provides an opportunity for hydrogen storage under low-stringency conditions. Physically adsorbed hydrogen molecules are weakly bound to a surface and, hence, are easily released. Among the various surface candidates, porous carbons appear to provide efficient hydrogen storage, with the advantages that porous carbon is relatively low-cost to produce and is easily prepared. In this review, we summarize the preparation methods, pore characteristics, and hydrogen storage capacities of representative nanoporous carbons, including activated carbons, zeolite-templated carbon, and carbide-derived carbon. We focus particularly on a series of nanoporous carbons developed recently: metal–organic framework-derived carbons, which exhibit promising properties for use in hydrogen storage applications

MAIR: Multi-view Attention Inverse Rendering with 3D Spatially-Varying Lighting Estimation

We propose a scene-level inverse rendering framework that uses multi-view images to decompose the scene into geometry, a SVBRDF, and 3D spatially-varying lighting. Because multi-view images provide a variety of information about the scene, multi-view images in object-level inverse rendering have been taken for granted. However, owing to the absence of multi-view HDR synthetic dataset, scene-level inverse rendering has mainly been studied using single-view image. We were able to successfully perform scene-level inverse rendering using multi-view images by expanding OpenRooms dataset and designing efficient pipelines to handle multi-view images, and splitting spatially-varying lighting. Our experiments show that the proposed method not only achieves better performance than single-view-based methods, but also achieves robust performance on unseen real-world scene. Also, our sophisticated 3D spatially-varying lighting volume allows for photorealistic object insertion in any 3D location.Comment: Accepted by CVPR 2023; Project Page is https://bring728.github.io/mair.project

General Relationship between Hydrogen Adsorption Capacities at 77 and 298 K and Pore Characteristics of the Porous Adsorbents

The hydrogen adsorption isotherms of six metal–organic frameworks (MOFs) and three microporous carbons, measured at 77 K (up to 1 bar) and 298 K (up to 100 bar), have been systematically examined for correlations with their pore characteristics. From the obtained correlations, H₂ adsorption was found to occur preferentially in ultrafine pores at both 77 K (≤1 bar) and 298 K (100 bar), irrespective of the adsorbent. This represents the first experimental evidence that ultrafine pores in MOFs improve the efficiency of H₂ adsorption at 298 K and at high pressures, indicating that that the low H₂ storage capacities of reported ultrahigh microporous MOFs at 298 K result from the prominence of micropores with diameters 1–2 nm, which are inadequate at 298 K and high pressures. Furthermore, these correlations suggest strong links between the H₂ storage capacities at 77 and 298 K, which offer an easy method for predicting H₂ adsorption capacities under unapproachable conditions. This study provides guidance in the development of new MOFs or other adsorbents with an optimized H₂ storage capacity at near-ambient temperatures and a swift screening method of newly synthesized porous adsorbents

Highly Reproducible Thermocontrolled Electrospun Fiber Based Organic Photovoltaic Devices

In this work, we examined the reasons underlying the humidity-induced morphological changes of electrospun fibers and suggest a method of controlling the electrospun fiber morphology under high humidity conditions. We fabricated OPV devices composed of electrospun fibers, and the performance of the OPV devices depends significantly on the fiber morphology. The evaporation rate of a solvent at various relative humidity was measured to investigate the effects of the relative humidity during electrospinning process. The beaded nanofiber morphology of electrospun fibers was originated due to slow solvent evaporation rate under high humidity conditions. To increase the evaporation rate under high humidity conditions, warm air was applied to the electrospinning system. The beads that would have formed on the electrospun fibers were completely avoided, and the power conversion efficiencies of OPV devices fabricated under high humidity conditions could be restored. These results highlight the simplicity and effectiveness of the proposed method for improving the reproducibility of electrospun nanofibers and performances of devices consisting of the electrospun nanofibers, regardless of the relative humidity

MOF-Derived Hierarchically Porous Carbon with Exceptional Porosity and Hydrogen Storage Capacity

Highly porous carbon has played an important role in tackling down the energy and environmental problems due to their attractive features such as high specific surface area (SSA), stability, and mass productivity. Especially, the desirable characteristics of the highly porous carbon such as lightweight, fast adsorption/desorption kinetics, and high SSA have attracted extensive attention in the “hydrogen storage” application which is a main bottleneck for the realization of on-board hydrogen fuel cell vehicles. We herein presented porous carbon with hierarchical pore structure derived from highly crystalline metal organic frameworks (denoted as MOF-derived carbon: MDC) without any carbon source and showed it as a promising hydrogen storage adsorbent. MDCs can be fabricated by a simple heat adjustment of MOFs without complicated process and environmental burden. The MDC displayed hierarchical pore structures with high ultramicroporosity, high SSA, and very high total pore volume. Due to its exceptional porosity, MDCs exhibited reversible H₂ storage capacities at certain conditions that were better than those of previously reported porous carbons and MOFs

Preparation and Exceptional Lithium Anodic Performance of Porous Carbon-Coated ZnO Quantum Dots Derived from a Metal–Organic Framework

Hierarchically porous carbon-coated ZnO quantum dots (QDs) (∼3.5 nm) were synthesized by a one-step controlled pyrolysis of the metal–organic framework IRMOF-1. We have demonstrated a scalable and facile synthesis of carbon-coated ZnO QDs without agglomeration by structural reorganization. This unique microstructure exhibits outstanding electrochemical performance (capacity, cyclability, and rate capability) when evaluated as an anode material for lithium ion batteries

Importance of broken geometric symmetry of single-atom Pt sites for efficient electrocatalysis

Abstract Platinum single-atom catalysts hold promise as a new frontier in heterogeneous electrocatalysis. However, the exact chemical nature of active Pt sites is highly elusive, arousing many hypotheses to compensate for the significant discrepancies between experiments and theories. Here, we identify the stabilization of low-coordinated PtII species on carbon-based Pt single-atom catalysts, which have rarely been found as reaction intermediates of homogeneous PtII catalysts but have often been proposed as catalytic sites for Pt single-atom catalysts from theory. Advanced online spectroscopic studies reveal multiple identities of PtII moieties on the single-atom catalysts beyond ideally four-coordinated PtII–N4. Notably, decreasing Pt content to 0.15 wt.% enables the differentiation of low-coordinated PtII species from the four-coordinated ones, demonstrating their critical role in the chlorine evolution reaction. This study may afford general guidelines for achieving a high electrocatalytic performance of carbon-based single-atom catalysts based on other d 8 metal ions

Hidden Second Oxidation Step of Hummers Method

Hummers method has been used for 50 years to prepare graphene oxide (GO) by oxidizing graphite using Mn₂O₇. In this work, a new angle on Hummers method is described. The oxidation procedure before the addition of water, which has been respected as the main oxidation step of Hummers method, is named <i>step I oxidation</i>, and the widely ignored further oxidation step after the addition of water is named <i>step II oxidation</i>. The chemical and structural evolutions during step II oxidation was demonstrated for the first time using various techniques including atomic force microscopy (AFM), dynamic light scattering (DLS), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible light (UV–vis) spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), ¹³C nuclear magnetic resonance (NMR), and zeta-potentiometry. Step II oxidation influences the size of GO, defects within the layers, and functional groups on the surface, which affect the thermal stability of GO and the properties of resultant thermally reduced GO. This work provides new chemical insights into GO and guidelines for preparation of tailor-fitted GO