Three-dimensional stacked graphite sheets with exposed edge-defects as Pt-based catalyst support

Platinum compounds constructing interface structure strategies for electrolysis hydrogen production

With the continuous growth of global energy demand, designing efficient hydrogen evolution reaction (HER) catalysts has become increasingly important. However, current interface structure synthesis strategies for platinum-based compounds are not yet adequate, limiting their application efficiency in hydrogen production. Therefore, this paper reviews a series of interface construction strategies, including the solvothermal method, gas-phase chemical method, heat treatment method, reduction method, electromagnetic synthesis method, electrochemical method, constructing heterojunctions method and constructing substrates method. These methods significantly enhance the overall performance of platinum-based catalysts by optimizing the interactions between the catalyst and support materials, improving electron transfer efficiency, and increasing the exposed area of active sites. Additionally, this paper introduces various interface structure strategies that can increase HER active sites, such as single-atom catalysts, diatomic catalysts, nanoparticles, nanowires, nanotubes, and porous structures. These nanostructures further enhance catalytic activity and stability by increasing the specific surface area and providing abundant reaction sites. Furthermore, this paper thoroughly elucidates the mechanisms of the HER in acidic and alkaline media, exploring the key factors for optimizing catalyst performance under different pH conditions. By understanding the HER mechanisms and combining advanced interface construction strategies with diverse nanostructure designs, researchers can better construct interfaces and design nanostructures, thereby developing platinum-based catalysts that are efficient, stable, and economical. This review provides a systematic guide for constructing interface structures of platinum compounds, aiming to promote the sustainable development of hydrogen energy technologies, facilitate their widespread application in the global energy transition, and contribute to achieving carbon neutrality goals and addressing increasingly severe environmental challenges.

Resilient and Reversible Phosphotungstic Acid Passivated Zinc Anode

Aqueous zinc ion batteries (ZIBs) present a compelling solution for grid-scale energy storage, which is crucial for integrating renewable energy resources into the electric infrastructure. The cycling stability of ZIBs hinges on the electrochemical reversibility of the zinc anode, which is often compromised by corrosion and dendritic zinc deposition. Here, we present a straightforward surface passivation strategy that significantly enhances the cycling stability of zinc anodes. By immersing zinc in a solution of phosphotungstic acid, we promoted the dominance of the 002 plane of zinc's hexagonal structure. This process facilitates the creation of a uniform nucleation and protective layer on the native zinc surface, resulting in a more uniform plating-stripping process and increased corrosion resistance. In symmetric cells, the passivated zinc exhibits a capacity retention of 68.7% after 1000 cycles at a current density of 1.0 Ag1-, whereas untreated zinc anodes retain only 7.4% of capacity under identical conditions. In full cell zinc iodine batteries employing the passivated zinc anode, over 1000 stable charge-discharge cycles were achieved at a current density of 20 mA cm-2, with approximately 96% Coulombic efficiency (CE), 86% voltage efficiency (VE), and 82% energy efficiency (EE). This study demonstrates a promising pathway for the construction and upscaling of flow batteries with high capacity and low cost.

The Enhancing Effect of Stable Oxygen Functional Groups on Porous-Carbon-Supported Pt Catalysts for Alkaline Hydrogen Evolution

The oxygen functionalization of carbon materials has widely been employed to improve the catalytic performance of carbon-supported Pt (Pt/C) catalysts. Hydrochloric acid (HCl) has often been employed to clean carbons during the preparation of carbon materials. However, the effect of oxygen functionalization through a HCl treatment of porous carbon (PC) supports on the performance of the alkaline hydrogen evolution reaction (HER) has rarely been investigated. Herein, the impact of HCl combined with the heat treatment of PC supports on the HER performance of Pt/C catalysts has been comprehensively investigated. The structural characterizations revealed similar structures of pristine and modified PC. Nevertheless, the HCl treatment resulted in abundant hydroxyl and carboxyl groups and the further heat treatment formed thermally stable carbonyl and ether groups. Among the catalysts, Pt loading on the HCl-treated PC followed by a heat treatment at 700 °C (Pt/PC-H-700) exhibited elevated HER activity with a lower overpotential of 50 mV at 10 mA cm^-2 when compared to the unmodified Pt/PC (89 mV). Pt/PC-H-700 also exhibited better durability than the Pt/PC. Overall, novel insights into the impact of the surface chemistry properties of porous carbon supports on the HER performance of Pt/C catalysts were provided, which were useful for highlighting the feasible improvement of HER performances by regulating the surface oxygen species of porous carbon supports.

Ethanol Solvent Used in Constructing Ultra-Low-Temperature Zinc-Ion Capacitors with a Long Cycling Life

Zinc-ion capacitors (ZICs) gain enormous attraction for their high power density, low cost, and long life, but their poor low-temperature performance is still a challenge due to the dissatisfactory freezing point of aqueous electrolyte solution. It is difficult for them to meet the requirements in cold environments as well as the extreme low temperature and severe temperature fluctuations in aerospace environments. Herein, ethanol (EtOH) solvent with ZnCl₂ is used as an electrolyte to address these issues. Benefiting from the low freezing point (-114 °C) of EtOH, the ZIC with the ZnCl₂/EtOH electrolyte can be operated at an ultralow temperature of -78 °C. It also demonstrates long cycling stability over 30,000 cycles. Such an enhancement is attributed to the unique properties of [ZnCl(EtOH)₅]⁺ that can stabilize the coordination environment of Zn²⁺, slow the diffusivity, and raise the nucleation overpotential, leading to uniform Zn plating/stripping and subsequently suppressing dendrite growth. Meanwhile, the lower activation energy in ZnCl₂/EtOH than that in ZnSO₄/H₂O electrolytes endows the ZIC excellent charge transfer properties. This work provides a fascinating electrolyte and a feasible pathway for ultra-low-temperature ZICs with a long cycling life.

Enhanced stability of sub-nanometric iridium decorated graphitic carbon nitride for H2 production upon hydrous hydrazine decomposition

Stabilizing metal nanoparticles is vital for large scale implementations of supported metal catalysts, particularly for a sustainable transition to clean energy, e.g., H₂ production. In this work, iridium sub-nanometric particles were deposited on commercial graphite and on graphitic carbon nitride by a wet impregnation method to investigate the metal-support interaction during the hydrous hydrazine decomposition reaction. To establish a structure-activity relationship, samples were characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. The catalytic performance of the synthesized materials was evaluated under mild reaction conditions, i.e. 323 K and ambient pressure. The results showed that graphitic carbon nitride (GCN) enhances the stability of Ir nanoparticles compared to graphite, while maintaining remarkable activity and selectivity. Simulation techniques including Genetic Algorithm geometry screening and electronic structure analyses were employed to provide a valuable atomic level understanding of the metal-support interactions. N anchoring sites of GCN were found to minimise the thermodynamic driving force of coalescence, thus improving the catalyst stability, as well as to lead charge redistributions in the cluster improving the resistance to poisoning by decomposition intermediates.

Graphite Nanoflake-Modified Mo2C with Ameliorated Interfacial Interaction as an Electrocatalyst for Hydrogen Evolution Reaction

Molybdenum carbide (Mo₂C) is anticipated to be a promising electrocatalyst for electrocatalytic hydrogen production due to its low cost, resourceful property, prominent stability, and Pt-like electrocatalytic activity. The rational design of Mo₂C-based electrocatalysts is expected to improve hydrogen evolution reaction (HER) performance, especially by constructing ultrasmall Mo₂C particles and appropriate interfaces. Herein, composites of molybdenum carbide (Mo₂C) quantum dots anchored on graphite nanoflakes (Mo₂C/G) were fabricated, which realized a stable overpotential of 136 mV at 10 mA cm^-2 for the HER with a small Tafel slope of 76.81 mV dec^-1 in alkaline media, and operated stably over 10 h and 2000 cycles. The superior HER performance can be attributed to the fact that graphite nanoflakes could act as a matrix to disperse Mo₂C as quantum dots to expose more active sites and guarantee high electronic conductivity and, more importantly, provide ameliorated interfacial interaction between Mo₂C and graphite nanoflakes with appropriate hydrogen binding energy and charge density distribution. To further explore which kind of interfacial interaction is more favorable to improve the HER performance, density functional theory calculations and corresponding contrast experiments were also performed, and it was interesting to prove that Mo₂C quantum dots anchored to the basal planes of defective graphite nanoflakes exhibit better electrochemical performance than those anchored on the edges.

Designing interphases for practical aqueous zinc flow batteries with high power density and high areal capacity

Aqueous zinc flow batteries (AZFBs) with high power density and high areal capacity are attractive, both in terms of cost and safety. A number of fundamental challenges associated with out-of-plane growth and undesirable side reactions on the anode side, as well as sluggish reaction kinetics and active material loss on the cathode side, limit practical deployment of these batteries. We investigated artificial interphases created using a simple electrospray methodology as a strategy for addressing each of these challenges. The effectiveness of the electrospray interphases in full cell zinc-iodine flow batteries was evaluated and reported; it is possible to simultaneously achieve high power density [115 milliwatts per square centimeter (mW/cm²)] and high areal capacity [25 milliampere hour per square centimeter (mA·hour/cm²)]. Last, we extended it to aqueous zinc-bromine and zinc-vanadium flow batteries of contemporary interest. It is again found that high power density (255 and 260 mW/cm², respectively) and high areal capacity (20 mA·hour/cm²) can be simultaneously achieved in AZFBs.