Intrinsically microporous polymer slows down fuel cell catalyst corrosion

The limited stability of fuel cell cathode catalysts causes a significant loss of operational cell voltage with commercial Pt-based catalysts, which hinders the wider commercialization of fuel cell technologies. We demonstrate beneficial effects of a highly rigid and porous polymer of intrinsic microporosity (PIM-EA-TB with BET surface area 1027 m2 g−1) in accelerated catalyst corrosion experiments. Porous films of PIM-EA-TB offer an effective protective matrix for the prevention of Pt/C catalyst corrosion without impeding flux of reagents. The results of electrochemical cycling tests show that the PIM-EA-TB protected Pt/C (denoted here as PIM@Pt/C) exhibit a significantly enhanced durability as compared to a conventional Pt/C catalyst. Keywords: Electrocatalysis, Fuel cells, Membrane, Stabilization, Corrosio

Metal Organic Framework Glasses: a New Platform for Electrocatalysis?

International audienceMetal organic framework (MOF) glasses are a coordination network of metal nodes and organic ligands as an undercooled frozen-in liquid, and have therefore broadened the potential of MOF materials in the fundamental research and application scenarios. On the road to deploying MOF glasses as electrocatalysts, it remains several basic scientific hurdles although MOF glasses not only inherit the structural merits of MOFs but also endow with active catalytic features including concentrated defects, metal centers and disorder structure etc. The research on the ionic conductivity, catalytic stability and reactivity of MOF glasses has yielded scientific insights towards its electrocatalytic applications. Here, we first comb the history, definition and basic properties of MOF glasses. Then, we identify the main synthetic methods and characterization techniques. Finally, we advance the potentials and challenges of MOF glasses as electrocatalysts in furthering the understanding of these themes

Advances and challenges in designing MXene quantum dots for sensors

Abstract MXene quantum dots (MQDs) sensor is a promising platform for identifying target analytes by sensing fluorescence, electrochemical signals, photoluminescence, biomedical, and so on. On the way to designing MQDs in the sensors, substantial progress has been made with basic scientific and technological hurdles remaining. Combining specific functional designs of MQDs with mechanistic understanding provides new research prospects and technology opportunities even at the industrial level. However, MQDs must be able to detect target analytes with higher sensitivity, robust stability, and applied compatibility. Here, we review the recent advances and challenges in the synthetic strategies and rational design of MQDs. By zooming in on several representative examples, we discuss the existing potentials of MQDs in the application of fluorescence, electrochemical luminescence, photoluminescence, colorimetric/fluorescent dual‐mode, and biomedical sensors. Finally, we identify the opportunities and challenges to further understanding of MQDs sensors

Zn 2+ pre‐intercalation stabilizes the tunnel structure of MnO2 nanowires and enables zinc‐ion hybrid supercapacitor of battery‐level energy density

Although there has been tremendous progress in exploring new configurations of zinc-ion hybrid supercapacitors (Zn-HSCs) recently, the much lower energy density, especially the much lower areal energy density compared with that of the rechargeable battery, is still the bottleneck, which is impeding their wide applications in wearable devices. Herein, the pre-intercalation of Zn which gives rise to a highly stable tunnel structure of ZnMnO in nanowire form that are grown on flexible carbon cloth with a disruptively large mass loading of 12 mg cm is reported. More interestingly, the ZnMnO nanowires of tunnel structure enable an ultrahigh areal energy density and power density, when they are employed as the cathode in Zn-HSCs. The achieved areal capacitance of up to 1745.8 mF cm at 2 mA cm, and the remarkable areal energy density of 969.9 µWh cm are comparable favorably with those of Zn-ion batteries. When integrated into a quasi-solid-state device, they also endow outstanding mechanical flexibility. The truly battery-level Zn-HSCs are timely in filling up of the battery-supercapacitor gap, and promise applications in the new generation flexible and wearable devices

In situ confined vertical growth of Co2.5Ni0.5Si2O5(OH)4 nanoarrays on rGO for an efficient oxygen evolution reaction

Rational design of oxygen evolution reaction (OER) catalysts at low cost would greatly benefit the economy. Taking advantage of earth-abundant elements Si, Co and Ni, we produce a unique-structure where cobalt-nickel silicate hydroxide [Co2.5Ni0.5Si2O5(OH)4] is vertically grown on a reduced graphene oxide (rGO) support (CNS@rGO). This is developed as a low-cost and prospective OER catalyst. Compared to cobalt or nickel silicate hydroxide@rGO (CS@rGO and NS@rGO, respectively) nanoarrays, the bimetal CNS@rGO nanoarray exhibits impressive OER performance with an overpotential of 307 ​mV@10 ​mA ​cm−2. This value is higher than that of CS@rGO and NS@rGO. The CNS@rGO nanoarray has an overpotential of 446 ​mV@100 ​mA ​cm−2, about 1.4 times that of the commercial RuO2 electrocatalyst. The achieved OER activity is superior to the state-of-the-art metal oxides/hydroxides and their derivatives. The vertically grown nanostructure and optimized metal-support electronic interactions play an indispensable role for OER performance improvement, including a fast electron transfer pathway, short proton/electron diffusion distance, more active metal centers, as well as optimized dual-atomic electron density. Taking advantage of interlay chemical regulation and the in-situ growth method, the advanced-structural CNS@rGO nanoarrays provide a new horizon to the rational and flexible design of efficient and promising OER electrocatalysts

Transforming Two-Dimensional Boron Carbide into Boron and Chlorine Dual-Doped Carbon Nanotubes by Chlorination for Efficient Oxygen Reduction

Our theoretical calculations suggest that the synergistic effect between the electron acceptor (B) and donor (Cl) in carbon nanotubes (CNTs) (BClCNTs) is the key to excellent oxygen reduction reaction (ORR) activity. However, the rational fabrication of BClCNTs is still an open question. Here, we first present a metal-free and controlled strategy for successful preparation of BClCNTs via chemically tailoring two-dimensional (2D) boron carbide (B₄C) with Cl₂. Accompanied by partial extraction of B atoms from B₄C with Cl₂, the residue B and C atoms combining with Cl atoms self-organize into nanotube microstructures. Significantly, the amount of heteroatoms (B and Cl) can be tuned in terms of altering chlorine-to-carbide molar ratios. As expected, as a metal-free ORR catalyst, the produced BClCNTs exhibit a higher onset potential (0.94 V vs a reversible hydrogen electrode; RHE) and half-wave potential (0.84 V) as well as greater stability than those of commercial Pt/C (0.92 and 0.80 V)

Cobalt-doping in hierarchical Ni3S2 nanorod arrays enables high areal capacitance

Areal capacitance is an important metrics for miniaturized capacitive energy storage devices due to the constraint of device area. In the present work, we proposed a free-standing hierarchical cobalt-doped Ni3S2 (Co-Ni3S2) nanorod arrays as a novel pseudocapacitive electrode to realize impressively high areal capacitance. With enhanced surface area donated by the introduction of cobalt, the Co-Ni3S2 nanorods exhibit an ultrahigh areal capacitance of 3.46 F cm−2 at 8 mA cm−2, which is more than three-fold over that of pristine Ni3S2. When coupled with an FeOOH anode, the fabricated Co-Ni3S2//FeOOH hybrid supercapacitor can deliver a large areal capacitance of 1.61 F cm−2, a peak energy density of 0.73 mW h cm−2, and a peak power density of 36.00 mW cm−2. Besides, the as-fabricated hybrid supercapacitor also exhibits stable capacitive performance (83.5% capacity retention after 5000 cycles). The advanced and stable Co-Ni3S2 electrode developed in this work is highly desirable for micro supercapacitor devices

Well-structured 3D channels within GO-based membranes enable ultrafast wastewater treatment

Graphene oxide (GO)-based membranes have been widely studied for realizing efficient wastewater treatment, due to their easily functionalizeable surfaces and tunable interlayer structures. However, the irregular structure of water channels within GO-based membrane has largely confined water permeance and prevented the simultaneously improvement of purification performance. Herein, we purposely construct the well-structured three-dimensional (3D) water channels featuring regular and negatively-charged properties in the GO/SiO2 composite membrane via in situ close-packing assembly of SiO2 nanoparticles onto GO nanosheets. Such regular 3D channels can improve the water permeance to a record-high value of 33,431.5 ± 559.9 L·m−2·h−1 (LMH) bar−1, which is several-fold higher than those of current state-of-the-art GO-based membranes. We further demonstrate that benefiting from negative charges on both GO and SiO2, these negatively-charged 3D channels enable the charge selectivity well toward dye in wastewater where the rejection for positive-charged and negative-charged dye molecules is 99.6% vs. 7.2%, respectively. The 3D channels can also accelerate oil/water (O/W) separation process, in which the O/W permeance and oil rejection can reach 19,589.2 ± 1,189.7 LMH bar−1 and 98.2%, respectively. The present work unveils the positive role of well-structured 3D channels on synchronizing the remarkable improvement of both water permeance and purification performance for highly efficient wastewater treatment

Bronze-type vanadium dioxide holey nanobelts as high performing cathode material for aqueous aluminium-ion battery

Aqueous rechargeable aluminium-ion batteries (AIBs) are promising post lithium-ion battery candidates. However, the capacity and cycling stability are limited by the cathode materials, hindering their widespread application. Herein, bronze-type vanadium dioxide (VO2–B) holey nanobelts have been designed as the cathode material to improve both the capacity and cycling stability for high-performance aqueous AIBs. Benefiting from the unique shear structure and two-dimensional holey nanobelt morphology, the VO2–B electrode delivers a superior specific capacity of up to 234 mA h g−1 at 150 mA g−1 and exhibits a high capacity retention of 77.2% over 1000 cycles at 1 A g−1, which are among the best cathode performances reported for aqueous AIBs. Moreover, a combination of electro-kinetic analysis and ex situ structural evolution characterization experiments reveals the reaction storage mechanism underlying the superior performance. Specifically, proton and Al3+ ions can reversibly co-intercalate/de-intercalate into/from VO2–B. The integration of shear structure and unique holey nanobelts may open the route to the design of high-performance cathodes for multi-valence ion batteries.National Research Foundation (NRF)Accepted versionThis work was financially supported by the National Research Foundation of Singapore (NRF) Investigatorship Award Number NRFI2017-08/NRF2016NRF-NRFI001-22

Single‐atom metal‐nitrogen‐carbon catalysts energize single molecule detection for biosensing

Abstract Biosensors featuring single molecule detection present huge opportunities as well as challenges in food safety inspection, disease diagnosis, and environmental monitoring. Single‐molecule detection is largely lacking of high enough activity, precision molecule selectivity, and understanding in the exact operating mechanism. Single‐atom catalysts (SACs), especially those metals‐nitrogen‐carbon that mimic the natural metalloenzyme structure, and with well‐defined metal atom bond configurations, high level of molecular selectivity, and easy fabrication, endow single molecule detections with practical‐use feasibilities. The recent advances in single‐atom catalysts also present new pathways in the key mechanism understandings. In this short review, we will first visit the brief history and advantages of SACs that have been explored only recently for molecule‐scale biosensors, where they are analogous and also differentiated from those nanozymes and natural metalloenzymes. Their applications in electrochemical, photochemical, and photoelectrochemical sensors are then discussed comprehensively by focusing on the different molecule‐scale sensing modes in achieving local coordination‐modulated signal amplifications. Finally, we identify new opportunities and challenges faced by these SACs‐based single molecule detections in the further development of biosensors