Mesoporous Pd@Ru Core-Shell Nanorods for Hydrogen Evolution Reaction in Alkaline Solution

Exploring the properties, types, and performance of atomic site catalysts in electrochemical hydrogen evolution reactions

Atomic site catalysts (ASCs) have recently gained prominence for their potential in the electrochemical hydrogen evolution reaction (HER) due to their exceptional activity, selectivity, and stability. ASCs with individual atoms dispersed on a support material, offer expanded surface areas and increased mass efficiency. This is because each atom in these catalysts serves as an active site, which enhances their catalytic activity. This review is focused on providing a detailed analysis of ASCs in the context of the HER. It will delve into their properties, types, and performance to provide a comprehensive understanding of their role in electrochemical HER processes. The introduction part underscores HER's significance in transitioning to sustainable energy sources and emphasizes the need for innovative catalysts like ASCs. The fundamentals of the HER section emphasizes the importance of understanding the HER and highlights the key role that catalysts play in HER. The review also explores the properties of ASCs with a specific emphasis on their atomic structure and categorizes the types based on their composition and structure. Within each category of ASCs, the review discusses their potential as catalysts for the HER. The performance section focuses on a thorough evaluation of ASCs in terms of their activity, selectivity, and stability in HER. The performance section assesses ASCs in terms of activity, selectivity, and stability, delving into reaction mechanisms via experimental and theoretical approaches, including density functional theory (DFT) studies. The review concludes by addressing ASC-related challenges in HER and proposing future research directions, aiming to inspire further innovation in sustainable catalysts for electrochemical HER.

Mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowire electrocatalyst for efficient oxygen reduction

The design of Pt-based nanoarchitectures with controllable compositions and morphologies is necessary to enhance their electrocatalytic activity. Herein, we report a rational design and synthesis of anisotropic mesoporous Pt@Pt-skin Pt₃Ni core-shell framework nanowires for high-efficient electrocatalysis. The catalyst has a uniform core-shell structure with an ultrathin atomic-jagged Pt nanowire core and a mesoporous Pt-skin Pt₃Ni framework shell, possessing high electrocatalytic activity, stability and Pt utilisation efficiency. For the oxygen reduction reaction, the anisotropic mesoporous Pt@Pt-skin Pt₃Ni core-shell framework nanowires demonstrated exceptional mass and specific activities of 6.69 A/mg_pt and 8.42 mA/cm² (at 0.9 V versus reversible hydrogen electrode), and the catalyst exhibited high stability with negligible activity decay after 50,000 cycles. The mesoporous Pt@Pt-skin Pt₃Ni core-shell framework nanowire configuration combines the advantages of three-dimensional open mesopore molecular accessibility and compressive Pt-skin surface strains, which results in more catalytically active sites and weakened chemisorption of oxygenated species, thus boosting its catalytic activity and stability towards electrocatalysis.

Alloying at a Subnanoscale Maximizes the Synergistic Effect on the Electrocatalytic Hydrogen Evolution

Bonding dissimilar elements to provide synergistic effects is an effective way to improve the performance of metal catalysts. However, as the properties become more dissimilar, achieving synergistic effects effectively becomes more difficult due to phase separation. Here we describe a comprehensive study on how subnanoscale alloying is always effective for inter-elemental synergy. Thirty-six combinations of both bimetallic subnanoparticles (SNPs) and nanoparticles (NPs) were studied systematically using atomic-resolution imaging and catalyst benchmarking based on the hydrogen evolution reaction (HER). Results revealed that SNPs always produce greater synergistic effects than NPs, the greatest synergistic effect was found for the combination of Pt and Zr. The atomic-scale miscibility and the associated modulation of electronic states at the subnanoscale were much different from those at the nanoscale, which was observed by annular-dark-field scanning transmission electron microscopy (ADF-STEM) and X-ray photoelectron spectroscopy (XPS), respectively.

Ordered micropattern arrays fabricated by lung-derived dECM hydrogels for chemotherapeutic drug screening

AIMS

This study aims to evaluate ECM-coated micropattern arrays derived from decellularization of native porcine lungs as a novel three-dimensional cell culture platform.

METHODS

ECM derived from decellularization of native porcine lungs was exploited to prepare hydrogels. Then, dECM-coated micropattern arrays were fabricated at four different diameters (50, 100, 150 and 200 ​μm) using polydimethylsiloxane (PDMS). Two lung cancer cell lines, A549 and H1299, were tested on a dECM-coated micropattern array as a novel culture platform for cell adhesion, distribution, proliferation, viability, phenotype expression, and drug screening to evaluate the cytotoxicity of paclitaxel, doxorubicin and cisplatin.

RESULTS

The ECM derived from decellularization of native porcine lungs supported cell adhesion, distribution, viability and proliferation better than collagen I and Matrigel as the coated matrix on the surface. Moreover, the optimal diameter of the micropattern arrays was 100-150 ​μm, as determined by measuring the morphology, viability, proliferation and phenotype of the cancer cell spheroids. Cell spheroids of A549 and H1299 on dECM-coated micropattern arrays showed chemoresistance to anticancer drugs compared to that of the monolayer. The different distributions of HIF-1α, MCL-1 (in the center) and Ki-67 and MRP2 (in the periphery) of the spheroids demonstrated the good establishment of basal-lateral polarity and explained the chemoresistance phenomenon of spheroids.

CONCLUSIONS

This novel three-dimensional cell culture platform is stable and reliable for anticancer drug testing. Drug screening in dECM-coated micropattern arrays provides a powerful alternative to existing methods for drug testing and metabolic profiling in the drug discovery process.

Amorphous materials for elementary-gas-involved electrocatalysis: an overview

Given the critical demands on energy conversion, storage, and transportation, tremendous interest has been devoted to the field of material development related to energy harvesting, recently. As the only route towards energy utilization, the carriers with the characteristics of low carbon are regarded as the future choice, e.g., hydrogen and ammonia. To this end, electrocatalysis provides a green way to access these substances. However, the unfulfilled conversion efficiency is the bottleneck for practical application. In this review, the promising characteristics of amorphous materials and the amorphous-induced electrocatalytic enhancement (AIEE) were emphasized. In the beginning, the characteristics of amorphous materials are briefly summarized. The basic mechanism of heterogeneous electrocatalytic reactions is illustrated, including the hydrogen/oxygen evolution and oxygen/nitrogen reduction. In the third part, the electrocatalytic performance of amorphous materials is discussed in detail, and the mechanism of AIEE is highlighted. In the last section of this review, the challenges and outlook for the development of amorphous enhanced electrocatalysis are presented.

Highly efficient sub-nanometer RuxCuyP2 nanoclusters designed for hydrogen evolution under alkaline media

Design of highly active and stable non-precious electrocatalysts towards hydrogen evolution reaction (HER) is a hot research topic in low cost, clean and sustainable hydrogen energy field, yet remaining the important challenge caused by the sluggish reaction kinetics for water-alkali electrolyzers. Herein, a robust electrocatalyst is proposed by designing a novel sub-nanometer of copper and ruthenium bimetallic phosphide nanoclusters (Ru_xCu_yP₂) supported on a graphited carbon nanofibers (CNF). Uniform Ru_xCu_yP₂ (~1.90 nm) on the surface of CNF are obtained by introducing the dispersed Ru, thereby improving the intrinsic activity for HER. On optimizing the Ru ratio, the (x = y = 1) RuCuP₂/CNF catalyst exhibits an excellent HER electroactivity with an overpotential of 10 mV in 1.0 M NaOH electrolyte to produce 10 mA cm^-2 current density, which is lower than commercial 20% Pt/C in alkaline solution. Moreover, the kinetic study demonstrated that electrochemical activation energies for HER of RuCuP₂/CNF is 20.7 kJ mol^-1 highest among different ratio bimetallic phosphide. This simple, cost-effective, and environmentally friendly methodology can pave the way for exploitation of bimetallic phosphide nanoclusters for catalyst design.

Low content Ru-incorporated Pd nanowires for bifunctional electrocatalysis

This paper reports the facile synthesis and characterization of carbon supported Pd nanowires with low Ru contents (nRuPd/C). An anti-galvanic replacement reaction involving the reduction of Ru(iii) ions by nanoporous Pd nanowires to form nRuPd alloy nanowires was observed. A series of nRuPd/C materials with various Ru/Pd ratios were prepared by the spontaneous deposition of a Ru cluster on a Pd nanowire core using different Ru precursor concentrations (RuCl₃ = 0.5, 1.0, 5.0 mM). The successful formation of low content Ru-incorporated Pd nanowires without individual Ru clusters were confirmed using physicochemical characterization. The electrocatalytic activity of the nRuPd/C for the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) in alkaline media was measured by RDE polarization experiments. The electrocatalytic activity varied greatly depending on the Ru content on the Pd nanowires. Among the catalysts, the prepared Pd nanowires incorporated with a very small amount of Ru (ca. 1.4 wt%) exhibited excellent electrocatalytic activity toward the ORR and HER: positive ORR/HER onset and E_1/2 potentials, higher n value, and lower Tafel slope.

The catalytic activity of Pd nanowires with low Ru contents showed superior bifunctional electrocatalytic performance towards both ORR and HER compared to the benchmarking Pt/C.

Fragment-interconnected nitrogen-doped porous carbon nanosheets loaded with platinum group metals for highly boosted hydrogen evolution reaction in alkaline solution

The rational design and preparation of advanced electrocatalysts for the hydrogen evolution reaction (HER) under alkaline conditions is the key to achieving sustainable hydrogen production. Herein, a new type of nitrogen-doped porous carbon nanosheets (NPCN) loaded with platinum group metals (Pd, Pt or Ru) were prepared. The introduction of melamine not only realized the doping of N-species, but also optimized the morphology and surface functional groups of the prepared catalysts. The prepared Pd-NPCN, Pt-NPCN and Ru-NPCN with a metal loading of about 10 wt% showed outstanding HER activity (21, 9 and 11 mv at 10 mA cm^-2 current density), small Tafel slopes (49, 30 and 30 mV dec^-1) and good stability in 1.0 M KOH. In addition, the mechanism of the introduction of melamine to improve the catalytic performance of HER was also discussed. Therefore, this work provides promising alternatives to traditional Pt-based catalysts, and is instructive for the design of high-efficiency alkaline HER catalysts.

Strong electrostatic adsorption-engaged fabrication of sub-3.0 nm PtRu alloy nanoparticles as synergistic electrocatalysts toward hydrogen evolution

Alloying of Pt with Ru to form ultrafine and well-defined PtRu alloy nanoparticles (NPs) for synergistically electrocatalytic hydrogen evolution is highly desirable but remains a synthetic challenge. Here, we report a strong electrostatic adsorption (SEA)-assisted fabrication of ultrafine and homogeneously distributed PtRu alloy NPs using ethylenediaminetetraacetic acid tetrasodium-derived carbon (EC) as a matrix. The O, N-rich EC with a hierarchically macro/meso/microporous structure and the SEA-assisted formation of the [Ru(bpy)₃][PtCl₆] complex ensure the successful generation of ultrasmall PtRu alloy NPs (2.93 nm in diameter) with high dispersion. The optimal PtRu/EC-700 delivers excellent electrocatalytic properties with an ultralow overpotential (η₁₀ = 18 mV), robust durability and good long-term stability for the alkaline hydrogen evolution reaction (HER). The ultrasmall PtRu alloy NPs with rich surface sites, the synergistic catalysis effect between Pt and Ru and the hierarchically macro/meso/microporous structure of O, N-rich EC cooperatively enhance the HER performance of PtRu/EC-700. This study provides an easy but effective way to construct metal alloy NPs with an ultrafine size and high dispersity for catalytic applications.

Mesoporous RhRu Nanosponges with Enhanced Water Dissociation toward Efficient Alkaline Hydrogen Evolution

Lowering the energy barrier of water dissociation is critical to achieving highly efficient hydrogen evolution in alkaline conditions. Herein, we reported mesoporous RhRu nanosponges with enhanced water dissociation behavior as a new class of high-performance electrocatalysts for alkaline hydrogen evolution reaction (HER). The obtained nanosponges have a binary alloy structure (fcc) and a highly porous structure with high surface area. Our RhRu catalyst displayed an outstanding HER activity with an overpotential of 25 mV at 10 mA cm^-2 and a Tafel slope of 47.5 mV dec^-1 in 1.0 M KOH, which significantly outperformed that of commercial Pt/C catalyst and was even comparable to the classic Pt/metal (hydro)oxide catalysts. Density functional theory (DFT) calculations disclosed that charge redistribution on the RhRu alloy surface enabled tuning of the Ru d-band center and then promoted the adsorption and dissociation of water molecules. Based on the experimental results and theoretical modeling, a bifunctional mechanism contributed to the remarkable alkaline HER activity on the RhRu catalyst surface.

Pd-Ru nanocatalysts derived from a Pd-induced aerogel for dramatic boosting of hydrogen release

Alloyed bimetallic Pd-Ru nanocatalysts prepared by in situ reduction of a mixture of a Ru(iii) source and a Pd(ii)@alkyne-PVA aerogel and characterized by TEM and XPS exhibit very highly catalytic activity towards hydrogen release from ammonia borane hydrolysis with a TOF value of 578.2 mol_H2 mol_cat^-1 min^-1.

Hollow Nanotube Ru/Cu2+1 O Supported on Copper Foam as a Bifunctional Catalyst for Overall Water Splitting

Hydrogen energy is considered as one of the ideal clean energies for solving the energy shortage and environmental issues, and developing highly efficient electrocatalysts for overall water splitting to produce hydrogen is still a huge challenge. Herein, for the first time, Ru-doped Cu₂₊₁ O vertically arranged nanotube arrays in situ grown on Cu foam (Ru/Cu₂₊₁ O NT/CuF) are reported and further investigated for their catalytic properties for overall water splitting. The Ru/Cu₂₊₁ O NT/CuF presents ultrahigh catalytic activities for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline conditions, and it exhibits a small overpotential of 32 mV at 10 mA cm^-2 in the HER, and only needs 210 mV overpotential to achieve a current density of 10 mA cm^-2 in the OER. Importantly, the alkaline electrolyzer using Ru/Cu₂₊₁ O NT/CuF as a bifunctional electrocatalyst only needs 1.53 V voltage to deliver a current density of 10 mA cm^-2 , which is much lower than the benchmark of IrO₂ (+)/Pt(-) counterpart (1.64 V at 10 mA cm^-2 ). The excellent performance of the Ru/Cu₂₊₁ O NT/CuF catalyst is attributed to its high conductive substrate and special Ru-doped nanotube structure, which provides a high electrochemical active surface area and 3D gas diffusion channel.

Atomically Dispersed Pt on Screw-like Pd/Au Core-shell Nanowires for Enhanced Electrocatalysis

Engineering noble metal nanostructures at the atomic level can significantly optimize their electrocatalytic performance and remarkably reduce their usage. We report the synthesis of atomically dispersed Pt on screw-like Pd/Au nanowires by using ultrafine Pd nanowires as seeds. Au can selectively grow on the surface of Pd nanowires by an island growth pattern to fabricate surface defect sites to load atomically dispersed Pt, which can be confirmed by X-ray absorption fine structure measurements and aberration corrected HRTEM images. The nanowires with 2.74 at % Pt exhibit superior HER properties in acidic solution with an overpotential of 20.6 mV at 10 mA cm^-2 and enhanced alkaline ORR performance with a mass activity over 15 times greater than the commercial platinum/carbon (Pt/C) catalysts.

Topological Formation of a Mo-Ni-Based Hollow Structure as a Highly Efficient Electrocatalyst for the Hydrogen Evolution Reaction in Alkaline Solutions

A Mo-Ni alloy has been demonstrated to be a benchmark noble-metal-free catalyst for the hydrogen evolution reaction (HER) in alkaline solutions. Nevertheless, further improvement on its catalytic activity is desired to meet industrial requirements. In this study, Mo-Ni-based hollow structures (MoNi-HS), backboned by MoO_{3- x} nanosheets and decorated with metallic MoNi₄ nanoparticles, were obtained via a topological transformation process by annealing MoNi-oxide hollow precursors in a reducing atmosphere. This hollow structure allowed for a large proportion of catalytic surface exposed in the electrolyte, leading to highly efficient utilization of active sites in the catalyst. As a result, robust catalytic activity toward HER was recorded in 1 M KOH electrolyte: a low overpotential of 38 mV to deliver a current density of 10 mA/cm² and a very small Tafel slope of 31.4 mV per dec. Such a remarkable performance of MoNi-HS even outperformed the catalytic activity of the commercial Pt/C electrocatalyst, addressing an effective strategy to promote the catalytic performance of noble-metal-free catalysts.

Ultrathin Rh nanosheets as a highly efficient bifunctional electrocatalyst for isopropanol-assisted overall water splitting

In this work, we synthesized ultrathin Rh nanosheets (Rh-NSs) with atomic thickness, which revealed excellent activity for the hydrogen evolution reaction (HER) and super activity and extraordinary selectivity for the isopropanol oxidation reaction (IOR) in alkaline medium. When using Rh-NSs as a bifunctional electrocatalyst for water electrolysis in the presence of isopropanol, a voltage of only 0.4 V was required for H2 production, accompanied by the production of valuable acetone at the anode.

One-pot aqueous synthesis of two-dimensional porous bimetallic PtPd alloyed nanosheets as highly active and durable electrocatalyst for boosting oxygen reduction and hydrogen evolution

Recently, two-dimensional materials have gained increasing research attention due to their large surface area, high physical and chemical stability, and excellent electrocatalytic performances. Herein, we reported a simple and fast one-pot aqueous method for synthesis of two-dimensional porous bimetallic PtPd alloyed nanosheets (NSs) using benzyldimethylhexadecylammonium chloride (HDBAC) as the capping agent and stabilizer. The formation mechanism involved the oriented attachment and self-assembly. The PtPd NSs exhibited excellent oxygen reduction reaction (ORR) activity with the positive shift (c.a. 43 mV) of the half-wave potential in 0.1 M KOH solution, clearly outperforming that of commercial Pt/C (50 wt%). Moreover, the as-prepared catalyst displayed 2.4 times enlargement in mass activity (MA, 382.10 mA mg^-1) and 3.5 times enhancement in specific activity (SA, 0.95 mA cm^-2) relative to those of Pt/C at 0.80 V. Meanwhile, the as-obtained catalyst demonstrated highly boosted hydrogen evolution reaction (HER) in 0.5 M H₂SO₄ electrolyte, surpassing that of Pt/C. These results reveal the practical applications of the catalyst in energy storage and conversion.

Shaping well-defined noble-metal-based nanostructures for fabricating high-performance electrocatalysts: advances and perspectives

This review highlights recent advances in shaping protocols and structure-activity relationships of noble-metal-based catalysts with well-defined nanostructures in electrochemical reactions.

Fabrication of uniform Ru-doped NiFe2O4 nanosheets as an efficient hydrogen evolution electrocatalyst

Ru-doped NiFe₂O₄ nanosheets exhibit outstanding electrocatalytic hydrogen evolution activity and stability.