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The development of active and stable platinum (Pt)-based oxygen reduction reaction (ORR) electrocatalysts with good resistance to poisoning is a prerequisite for widespread practical application of fuel cells. An effective strategy for enhancing the electrocatalytic performance is to tune or control the physicochemical state of the Pt surface. Herein, we show a general surface-engineering approach to prepare a range of nanostructured Pt alloys by coating with alloy PtBi shells. FePt@PtBi core-shell nanoparticles showed the best ORR performance with a mass activity of 0.96 A mgPt-1 and a specific activity of 2.06 mA cm-2 , respectively 7 times and 11 times those of the corresponding values for benchmark Pt/C. Moreover, FePt@PtBi shows much better tolerance to methanol and carbon monoxide than conventional Pt-based electrocatalysts. The observed comprehensive enhancement in ORR performance of FePt@PtBi can be attributed to the increased compressive strain of the Pt surface due to in-plane shearing resulting from the presence of the large Bi atoms in the surface-structured PtBi overlayers, as well as charge displacement via Pt-Bi bonding which mitigates crossover issues.

Bulk amorphous polymers become stretched and parallel-aligned under loading stress, and their intermolecular cooperation slows down the subsequent stress relaxation process. By means of dynamic Monte Carlo simulations, we employed the linear viscoelastic Maxwell model for stress relaxation of single polymers and investigated their intermolecular cooperation in the stress relaxation process of stretched and parallel-aligned bulk amorphous polymers. We carried out thermal fluctuation analysis on the reproduced Debye relaxation and Arrhenius fluid behaviors of bulk polymers. We found a transient state with stretch-coil coexistence among polymers in the stress relaxation process. Further structure analysis revealed a scenario of local jamming at the transient state, resulting in an entropy barrier for stretch-coil transition of partial polymers. The microscopic mechanism of intermolecular cooperation appears as unique to polymer stress relaxation, which interprets the hydrodynamic interactions as one of essential factors raising a high viscosity in bulk amorphous polymers. Our simulations set up a platform of molecular modeling in the study of polymer stress relaxation, which brought new insights into polymer dynamics and the related mechanical/rheological properties.

Applications of phthalocyanines (Pcs) in electrocatalysis—including the oxygen reduction reaction (ORR), the carbon dioxide reduction reaction (CO2RR), the oxygen evolution reaction (OER), and the hydrogen evolution reaction (HER)—have attracted considerable attention recently. Pcs and their derivatives are more attractive than many other macrocycles as electrocatalysts since, although they are structurally related to natural porphyrin complexes, they offer the advantages of low cost, facile synthesis and good chemical stability. Moreover, their high tailorability and structural diversity mean Pcs have great potential for application in electrochemical devices. Here we review the structure and composition of Pcs, methods of synthesis of Pcs and their analogues, as well as applications of Pc-based heterogeneous electrocatalysts. Optimization strategies for Pc-based materials for electrocatalysis of ORR, CO2RR, OER and HER are proposed, based on the mechanisms of the different electrochemical reactions. We also discuss the structure/composition–catalytic activity relationships for different Pc materials and Pc-based electrocatalysts in order to identify future practical applications. Finally, future opportunities and challenges in the use of molecular Pcs and Pc derivatives as electrocatalysts are discussed.

A rational porous structure can efficiently enhance the electrode reaction process. In this study, we fabricated a type of three-dimensional (3D)-ordered hierarchically porous carbon via a dual-template method to support ruthenium species as efficient cathodes towards the hydrogen evolution reaction (HER). The ordered hierarchical pores comprised of three levels of porous structure, including the inverse opal-structured macroporous carbon skeleton (ca. 150 nm), the internal-ordered mesoporous structure (ca. 5 nm), and abundant microporous structure (

Tailored single-atom catalysts can trigger breakthroughs in the development of high-performance and low-cost energy conversion systems, especially in the case of supported noble metal electrocatalysts. However, the weak interactions between unsaturated metal atoms and supports can result in metal dissolution or aggregation in a harsh electrochemical environment. Here we report a facile yet effective method to stabilize atomic Ru–N sites on boron-doped carbon by mild photo-activation. Owing to the presence of adjacent B/N co-doped pairs, Ru atoms are firmly anchored on Ru–N–B–C centers leading to an enhanced metal–support interaction, with a Gibbs free energy close to zero for adsorption of H*. The resulting highly stabilized atomic Ru has excellent catalytic activity with efficient metal utilization towards the hydrogen evolution reaction in either alkaline or acidic electrolyte (with turnover frequencies of 2.82 and 1.02 H2 per s, respectively), along with good rate capability and anti-reverse-current ability in long-term operation. This work opens a new route to prepare highly robust single-atom catalysts, which have good prospects for practical application in high-performance and low-cost electrochemical energy conversion devices.

As one of the efficient and classic nanoscale catalysts, Pt nanoparticles play predominant roles in multiple energy conversion systems, especially for electrochemical devices involving the oxygen reduction reaction (ORR). It is important to develop a scalable method for synthesis of more efficient Pt-based electrocatalysts with higher activity and stability. In this work, a low-loading Pt-based electrocatalyst (8.0 wt%) is fabricated by the galvanic replacement reaction, presenting well-dispersed Pt nanoparticles adjacent to atomic Ni–N–C complexes (Pt@NiNC). Due to the synergetic effect associated with the nanoscale/atomic scale joint active sites and the strong metal–support interaction, the resulting Pt@NiNC hybrid exhibits better ORR performance and higher mass activity than the benchmark Pt/C, as well as enhanced electrochemical stability. This research not only opens a new route to develop heterogeneous catalysts with multi-scale joint sites but also provides bright prospects for high-performance and low-cost energy conversion and storage.

How to produce expressive molecular representations is a fundamental challenge in artificial intelligence-driven drug discovery. Graph neural network (GNN) has emerged as a powerful technique for modeling molecular data. However, previous supervised approaches usually suffer from the scarcity of labeled data and poor generalization capability. Here, we propose a novel molecular pre-training graph-based deep learning framework, named MPG, that learns molecular representations from large-scale unlabeled molecules. In MPG, we proposed a powerful GNN for modelling molecular graph named MolGNet, and designed an effective self-supervised strategy for pre-training the model at both the node and graph-level. After pre-training on 11 million unlabeled molecules, we revealed that MolGNet can capture valuable chemical insights to produce interpretable representation. The pre-trained MolGNet can be fine-tuned with just one additional output layer to create state-of-the-art models for a wide range of drug discovery tasks, including molecular properties prediction, drug-drug interaction and drug-target interaction, on 14 benchmark datasets. The pre-trained MolGNet in MPG has the potential to become an advanced molecular encoder in the drug discovery pipeline.

Stretching of semicrystalline polymer materials is fundamentally important in their mechanical performance and industrial processing. By means of dynamic Monte Carlo simulations, we compared the parallel stretching processes between the initially bulk amorphous and semicrystalline polymers at various temperatures. In the early stage of stretching, semicrystalline polymers perform local and global melting-recrystallization behaviors at low and high temperatures, while the memory effects occur upon global melting-recrystallization at middle temperatures. However, the final crystallinities, crystalline bond orientations, chain-folding probabilities, residual stresses, and crystallite morphologies at high enough strains appear as the same at each temperature, irrelevant to the initially amorphous and semicrystalline polymers, indicating that the common post-growth melting-reorganization processes determine the final products. In addition, both final products harvest the highest crystallinities in the middle temperature region because the postgrowth stage yields the vast nuclei followed with less extent of crystal growth in the low temperature region and few nuclei followed with large extent of crystal growth in the high temperature region. Our observations imply that a large enough strain can effectively remove the thermal history of polymers, similar to the thermal treatment at a high enough temperature; therefore, the fracture strength of semicrystalline polymers depends upon their final structures in stretching, not related to their nascent semicrystalline structures.

Two-dimensional (2D) conjugated aromatic networks (CAN) have been fabricated by ball milling of polymeric cobalt phthalocyanine precursors edge-functionalized with different aromatic acid anhydride substituents. The optimal CAN, obtained by using tetraphenylphthalic anhydride, consists of uniform and thin (2.9 nm) layers with a high BET surface (92 m2 g-1), resulting in well-defined Co-N4 active sites with a high degree of exposure. Thence, this material exhibits excellent electrocatalytic oxygen reduction reaction (44 mA mgcat.-1). Compared to a benchmark Pt/C catalyst, this value denotes 1.2- and 6.0-fold enhancements, respectively, in terms of the mass of Pt and total Pt/C. When utilized as air electrode catalysts in Zn-air batteries, this material provides a maximum areal power density (137 mW cm-2) and mass power density (0.68 W mgcat.-1), values which also clearly surpass those of benchmark Pt/C catalyst. This support-free and pyrolysis-free strategy developed in this work delivers a novel route for the applications of 2D materials in clean energy conversion and storage.

Developing efficient and low-cost replacements for precious metals as electrocatalysts active in electrochemical reactions-the oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR)-is a top priority in renewable energy technology. In this work a highly active and very stable trifunctional electrocatalyst composed of Co

Two-dimensional conjugated aromatic networks (CAN) with ultra-thin conjugated layers (ca. 3.5 nm) and high single-metal-atom-site density (mass content of 10.7 wt %, and 0.73 metal atoms per nm2 ) are prepared via a facile pyrolysis-free route involving a one-step ball milling of the solid-phase-synthesized polyphthalocyanine. These materials display outstanding oxygen reduction reaction (ORR) mass activity of 47 mA mgcat.-1 represents 1.3- and 6.4-fold enhancements compared to Pt and Pt/C in benchmark Pt/C, respectively. Moreover, the primary Zn-air batteries constructed with CAN as an air electrode demonstrate a mass/volume power density of 880 W gcat.-1 /615 W cmcat.-3 and stable long-term operation for 100 h. This strategy offers a new way to design high-performance electrocatalysts with atomic precision for use in other energy-storage and conversion applications.

Breaking the electroneutrality of sp2 carbon lattice is a viable way for nanocarbon material to modulate the charge delocalization and to further alter the electrocatalytic activity. Positive charge spreadsheeting is preferable for catalyzing the oxygen reduction reaction (ORR) and other electrochemical reactions. Analogously to the case of intramolecular charge transfer by heteroatom doping, electrons in the conjugated carbon lattice can be redistributed by the intermolecular charge transfer from the nanocarbon material to the polyelectrolyte. A copolymeric electrolyte, epichlorohydrin-dimethylamine copolymer (EDC) was synthesized. The EDC-modified carbon nanotube (CNT) hybrid was subsequently fabricated by sonication treatment and served as a metal-free carbonaceous electrocatalyst with remarkable catalytic activity and stability. The resultant hybrid presents positive charge spreadsheeting on CNT as a result of the interfacial electron transfer from CNT to EDC. DFT calculations were further carried out to reveal that the enhancement of the wrapped EDC polyelectrolyte originates from the synergetic effect of the quaternary ammonium-hydroxyl covalently bonded structure. The CNT-EDC hybrid not only provides an atomically precise regulation to modulate nanocarbon materials from inactive carbonaceous materials into efficient metal-free catalysts, but it also opens new avenues to develop metal-free catalysts with well-defined and highly active sites.

How the repeating-unit chemistry dominates polymer viscoelasticity remains as unclear. We employed four-set interaction parameters to represent thermodynamic and kinetic aspects of local intrachain and interchain interactions between monomers, which characterize polymer repeating-unit chemistry. We performed kinetic Monte Carlo simulations of Debye stress relaxation in stretched and parallel-aligned bulk amorphous polymers and evaluated the relative importance of each interactions in the diffusion energy derived from their Arrhenius fluid behaviors. The results demonstrated that, under the same strengths, the kinetic aspects of intrachain and interchain interactions raise much higher diffusion energies than their thermodynamic aspects. We discussed the example case of polyethylene. Our work paves the way towards the prediction of the structure-property relationship of the mechanical properties in bulk amorphous polymers.

NiFe-based materials are excellent electrocatalysts for the oxygen evolution reaction (OER) to promise as replacements for Ru- and Ir-based anode materials for water splitting. In this work, NiFeOx clusters strongly coupled N-doped carbon (NiFeOx©NC) hybrid is prepared by a one-step electrodeposition process in an aqueous solution containing Ni2+, Fe3+, and carbon quantum dots. The highly coupled interface between the sub-nano NiFeOx clusters and N-doped carbon results in the enhanced OER performance superior to the commercial dimensionally stable anode (RuIr-based), as evidenced by its lower overpotential (195 mV at 10 mA cm−2) and faster kinetics (Tafel slope of 33 mV dec−1), along with the excellent long-term durability, rate capability and environmental adaptability. It is believed that the NiFeOx©NC hybrid and electrodeposition–electrocatalysis strategy developed in this work provide new possibilities for the development of clean electrochemical technology.

Developing efficient and low-cost replacements for precious metals as electrocatalysts active in electrochemical reactions-the oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR)-is a top priority in renewable energy technology. In this work a highly active and very stable trifunctional electrocatalyst composed of Co2 P embedded in Co, N, and P multi-doped carbon has been synthesized using zeolitic imidazolate frameworks as precursors. The synergistic effects between Co2 P and the multi-heteroatom-doped carbon substrates afford materials having electrocatalytic activities for HER, OER, and ORR, which are comparable-or even superior to-those of commercial RuO2 or Pt/C catalysts. Density functional theory calculations show that Co2 P has a higher density of states at the Fermi level than Con P (0 < n < 2), which promotes electron transfer and intermediates adsorption in the catalytic process. Zinc-air batteries and water splitting devices assembled using the materials as electrode electrocatalysts show good performance and outstanding stability. This work represents a breakthrough in improving the catalytic performance of non-precious metal electrocatalysts for OER, HER, and ORR, and opens new avenues for clean energy generation.