Supramolecular Polymer Intertwined Free-Standing Bifunctional Membrane Catalysts for All-Temperature Flexible Zn-Air Batteries

Expanding the frontiers of electrocatalysis: advanced theoretical methods for water splitting

Electrochemical water splitting, which encompasses the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), offers a promising route for sustainable hydrogen production. The development of efficient and cost-effective electrocatalysts is crucial for advancing this technology, especially given the reliance on expensive transition metals, such as Pt and Ir, in traditional catalysts. This review highlights recent advances in the design and optimization of electrocatalysts, focusing on density functional theory (DFT) as a key tool for understanding and improving catalytic performance in the HER and OER. We begin by exploring DFT-based approaches for evaluating catalytic activity under both acidic and alkaline conditions. The review then shifts to a material-oriented perspective, showcasing key catalyst materials and the theoretical strategies employed to enhance their performance. In addition, we discuss scaling relationships that exist between binding energies and electronic structures through the use of charge-density analysis and d-band theory. Advanced concepts, such as the effects of adsorbate coverage, solvation, and applied potential on catalytic behavior, are also discussed. We finally focus on integrating machine learning (ML) with DFT to enable high-throughput screening and accelerate the discovery of novel water-splitting catalysts. This comprehensive review underscores the pivotal role that DFT plays in advancing electrocatalyst design and highlights its potential for shaping the future of sustainable hydrogen production.

Recent Advances in Wide-Range Temperature Metal-CO2 Batteries: A Mini Review

The metal-carbon dioxide batteries, emerging as high-energy-density energy storage devices, enable direct CO2 utilization, offering promising prospects for CO2 capture and utilization, energy conversion, and storage. However, the electrochemical performance of M-CO2 batteries faces significant challenges, particularly at extreme temperatures. Issues such as high overpotential, poor charge reversibility, and cycling capacity decay arise from complex reaction interfaces, sluggish oxidation kinetics, inefficient catalysts, dendrite growth, and unstable electrolytes. Despite significant advancements at room temperature, limited research has focused on the performance of M-CO2 batteries across a wide-temperature range. This review examines the effects of low and high temperatures on M-CO2 battery components and their reaction mechanism, as well as the advancements made in extending operational ranges from room temperature to extremely low and high temperatures. It discusses strategies to enhance electrochemical performance at extreme temperatures and outlines opportunities, challenges, and future directions for the development of M-CO2 batteries.

Porous carbon-nanostructured electrocatalysts for zinc-air batteries: from materials design to applications

Zinc-air batteries (ZABs) are pivotal in the evolution of sustainable energy storage solutions, distinguished by their high energy density and minimal environmental footprint. The oxygen electrode, which relies on sophisticated porous carbon materials, is critical to operational efficiency. This review scrutinizes oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) processes in ZABs through advanced porous carbon applications. It delves into innovative synthesis techniques such as templating, chemical vapor deposition, and self-assembly that tailor pore structures for peak performance. The interactions between catalytic sites and carbon nanostructures, which significantly boost electrochemical performance, are highlighted. The manuscript discusses future strategies for overcoming current challenges by advancing catalytic efficiency and electrode design, emphasizing the integration of nano-engineering and materials science to foster ZABs with superior energy capacity and adaptability. Additionally, the review projects how ongoing research into carbon material properties could unlock new applications in other energy systems, potentially broadening the scope of ZAB technology. This paper integrates recent advancements in porous carbon materials, offering pivotal insights for next-generation high-performance ZAB development.

Atomically modulated Cu single-atom catalysts for oxygen reduction reactions towards high-power density Zn- and Al-air batteries

Herein, Cu single-atom-encapsulated hollow carbon-nitrogen spheres (CuSA@CNS) are fabricated through a solution process, confining optimal electronic structures reinforcing Cu-N4 active sites. CuSA@CNS demonstrate a remarkable half-wave potential of 0.95 V, mass activity, and a durability of 5000 cycles. Accordingly, CuSA@CNS present record-high power densities of 371 and 289 mW cm-2 for Zn- and Al-air batteries. The rechargeable Zn-air battery demonstrates an unprecedented small charge-discharge voltage and stable cycling for harsh operations at 50 mA cm-2, outperforming Pt/C.

Proton-Coupled Electron Transfer on Cu2O/Ti3C2Tx MXene for Propane (C3H8) Synthesis from Electrochemical CO2 Reduction

Electrochemical CO2 reduction reaction (CO2RR) to produce value-added multi-carbon chemicals has been an appealing approach to achieving environmentally friendly carbon neutrality in recent years. Despite extensive research focusing on the use of CO2 to produce high-value chemicals like high-energy-density hydrocarbons, there have been few reports on the production of propane (C3H8), which requires carbon chain elongation and protonation. A rationally designed 0D/2D hybrid Cu2O anchored-Ti3C2Tx MXene catalyst (Cu2O/MXene) is demonstrated with efficient CO2RR activity in an aqueous electrolyte to produce C3H8. As a result, a significantly high Faradaic efficiency (FE) of 3.3% is achieved for the synthesis of C3H8 via the CO2RR with Cu2O/MXene, which is ≈26 times higher than that of Cu/MXene prepared by the same hydrothermal process without NH4OH solution. Based on in-situ attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and density functional theory (DFT) calculations, it is proposed that the significant electrocatalytic conversion originated from the synergistic behavior of the Cu2O nanoparticles, which bound the *C2 intermediates, and the MXene that bound the *CO coupling to the C3 intermediate. The results disclose that the rationally designed MXene-based hybrid catalyst facilitates multi-carbon coupling as well as protonation, thereby manipulating the CO2RR pathway.

Modulating the Energy Barrier via the Synergism of Cu3P and CoP to Accelerate Kinetics for Bolstering Oxygen Electrocatalysis in Zn-Air Batteries

Modulating the energy barrier of reaction intermediates to surmount sluggish kinetics is an utterly intriguing strategy for amplifying the oxygen reduction reaction. Herein, a Cu3P/CoP hybrid is incorporated on hollow porous N-doped carbon nanospheres via dopamine self-polymerization and high-temperature treatment. The resultant Cu3P/CoP@NC showcases a favorable mass activity of 4.41 mA mg-1 and a kinetic current density of 2.38 mA cm-2. Strikingly, the catalyst endows the aqueous Zn-air battery (ZAB) with a large power density of 209.0 mW cm-2, superb cyclability over 317 h, and promising application prospects in flexible ZAB. Theoretical simulations reveal that Cu functions as a modulator to modify the free energy of intermediates and adsorbs the O2 on the Co sites, hence rushing the reaction kinetics. The open and hydrophilic hollow spherical mesoporous structure provides unimpeded channels for reactant diffusion and electrolyte penetration, whereas the exposed inner and outer surfaces can confer a plethora of accessible actives sites. This research establishes a feasible design concept to tune catalytic activity for non-noble metal materials by construction of a rational nanoframework.

Machine Learning-Assisted Study of RENxC6-x-Doped Graphene as Potential Electrocatalysts for Oxygen Electrode Reactions

In the application of renewable energy, the oxidation-reduction reaction (ORR) and oxygen evolution reaction (OER) are two crucial reactions. Single-atom catalysts (SACs) based on metal-doped graphene have been widely employed due to their high activity and high atom utilization efficiency. However, the catalytic activity is significantly influenced by different metals and local coordination, making it challenging to efficiently screen through either experimental or density functional theory (DFT) calculations. To address this issue, this study employed a combination of DFT calculations and machine learning (DFT-ML) to investigate rare earth-modified carbon-based (RENxC6-x) electrocatalysts. Based on computational data from 75 catalysts, we trained two ML models to capture the underlying patterns of physical properties and overpotential. Subsequently, the candidate catalysts were screened, leading to the discovery of four ORR catalysts, nine OER catalysts, and five bifunctional electrocatalysts, all of which were thoroughly validated for their stability. Lastly, by integrating the ML models with the SHAP analysis framework, we revealed the influence of atomic radius, Pauling electronegativity, and other features on the catalytic activity. Additionally, we analyzed the physicochemical properties of potential catalysts through DFT calculations. The revolutionary DFT-ML approach provides a crucial driving force for the design and synthesis of potential catalysts in subsequent studies.

Li, Na, K, Mg, Zn, Al, and Ca Anode Interface Chemistries Developed by Solid-State Electrolytes

Solid-state batteries (SSBs) have received significant attention due to their high energy density, reversible cycle life, and safe operations relative to commercial Li-ion batteries using flammable liquid electrolytes. This review presents the fundamentals, structures, thermodynamics, chemistries, and electrochemical kinetics of desirable solid electrolyte interphase (SEI) required to meet the practical requirements of reversible anodes. Theoretical and experimental insights for metal nucleation, deposition, and stripping for the reversible cycling of metal anodes are provided. Ion transport mechanisms and state-of-the-art solid-state electrolytes (SEs) are discussed for realizing high-performance cells. The interface challenges and strategies are also concerned with the integration of SEs, anodes, and cathodes for large-scale SSBs in terms of physical/chemical contacts, space-charge layer, interdiffusion, lattice-mismatch, dendritic growth, chemical reactivity of SEI, current collectors, and thermal instability. The recent innovations for anode interface chemistries developed by SEs are highlighted with monovalent (lithium (Li+ ), sodium (Na+ ), potassium (K+ )) and multivalent (magnesium (Mg2+ ), zinc (Zn2+ ), aluminum (Al3+ ), calcium (Ca2+ )) cation carriers (i.e., lithium-metal, lithium-sulfur, sodium-metal, potassium-ion, magnesium-ion, zinc-metal, aluminum-ion, and calcium-ion batteries) compared to those of liquid counterparts.

Heterointerface promoted trifunctional electrocatalysts for all temperature high-performance rechargeable Zn-air batteries

The rational design of wide-temperature operating Zn-air batteries is crucial for their practical applications. However, the fundamental challenges remain; the limitation of the sluggish oxygen redox kinetics, insufficient active sites, and poor efficiency/cycle lifespan. Here we present heterointerface-promoted sulfur-deficient cobalt-tin-sulfur (CoS_1-δ/SnS_2-δ) trifunctional electrocatalysts by a facile solvothermal solution-phase approach. The CoS_1-δ/SnS_2-δ displays superb trifunctional activities, precisely a record-level oxygen bifunctional activity of 0.57 V (E_1/2 = 0.90 V and E_j=10 = 1.47 V) and a hydrogen evolution overpotential (41 mV), outperforming those of Pt/C and RuO₂. Theoretical calculations reveal the modulation of the electronic structures and d-band centers that endorse fast electron/proton transport for the hetero-interface and avoid the strong adsorption of intermediate species. The alkaline Zn-air batteries with CoS_1-δ/SnS_2-δ manifest record-high power density of 249 mW cm^-2 and long-cycle life for >1000 cycles under harsh operations of 20 mA cm^-2, surpassing those of Pt/C + RuO₂ and previous state-of-the-art catalysts. Furthermore, the solid-state flexible Zn-air battery also displays remarkable performance with an energy density of 1077 Wh kg^-1, >690 cycles for 50 mA cm^-2, and a wide operating temperature from +80 to -40 °C with 85% capacity retention, which provides insights for practical Zn-air batteries.

Flexible Solid-State Metal-Air Batteries: The Booming of Portable Energy Supplies

The rapid development of portable and wearable electronics has given rise to new challenges and provoked research in flexible, lightweight, and affordable energy storage devices. Flexible solid-state metal-air batteries (FSSMABs) are considered promising candidates, owing to their large energy density, mechanical flexibility, and durability. However, the practical applications of FSSMABs require further improvement to meet the demands of long-term stability, high power density, and large operating voltage. This Review presents a detailed discussion of innovative electrocatalysts for the air cathode, followed by a sequential overview of high-performance solid-state electrolytes and metal anodes, and a summary of the current challenges and future perspectives of FSSMABs to promote practical application and large-scale commercialization in the near future.

An Air-Rechargeable Zn Battery Enabled by Organic-Inorganic Hybrid Cathode

Self-charging power systems collecting energy harvesting technology and batteries are attracting extensive attention. To solve the disadvantages of the traditional integrated system, such as highly dependent on energy supply and complex structure, an air-rechargeable Zn battery based on MoS2/PANI cathode is reported. Benefited from the excellent conductivity desolvation shield of PANI, the MoS2/PANI cathode exhibits ultra-high capacity (304.98 mAh g-1 in N2 and 351.25 mAh g-1 in air). In particular, this battery has the ability to collect, convert and store energy simultaneously by an air-rechargeable process of the spontaneous redox reaction between the discharged cathode and O2 from air. The air-rechargeable Zn batteries display a high open-circuit voltage (1.15 V), an unforgettable discharge capacity (316.09 mAh g-1 and the air-rechargeable depth is 89.99%) and good air-recharging stability (291.22 mAh g-1 after 50 air recharging/galvanostatic current discharge cycle). Most importantly, both our quasi-solid zinc ion batteries and batteries modules have excellent performance and practicability. This work will provide a promising research direction for the material design and device assembly of the next-generation self-powered system.