Interface and defect engineering of hybrid nanostructures toward an efficient HER catalyst

Ultra-Low-Loaded Platinum Bonded Hexagonal Boron Nitride as Stable Electrocatalyst for Hydrogen Generation

Chemical stability of hexagonal boron nitride (hBN) ultrathin layers in harsh electrolytes and the availability of nitrogen site in hBN to stabilize metals like Pt are used here to develop a high intrinsic activity hydrogen evolution reaction (HER) catalyst having low loaded Pt (5 weight% or <1 atomic%). A catalyst having a nonzero oxidation state for Pt (with a Pt-N bonding) is shown to be HER active even with low catalyst loadings (0.114 mgcm-2). Electronic modification of the shear exfoliated hBN sheets is achieved by Au nanoparticle-based surface decoration (hBN_Au), and further anchoring with Pt develops a catalyst (hBN_Au_Pt) with high turnover frequency for HER (∼15). The hBN_Au_Pt is shown to be a highly durable catalyst even after the accelerated durability test for 10000 cycles and temperature annealing at 100 °C. Density functional theory based calculations gave insights in to the electronic modifications of hBN with Au and the catalytic activity of the hBN_Au_Pt system, in line with the experimental studies, indicating the demonstration of a new class of catalyst system devoid of issues such as carbon corrosion and Pt leaching.

Design and multilevel regulation of transition metal phosphides for efficient and industrial water electrolysis

Renewable energy electrolysis of water to produce hydrogen is an effective measure to break the energy dilemma. However, achieving activity and stability at a high current density is still a key problem in water electrolyzers. Transition metal phosphides (TMPs), with high activity and relative inexpensiveness, have become excellent candidates for the production of highly pure green hydrogen for industrial applications. In this mini-review, multilevel regulation strategies including nanoscale control, surface composition and interface structure design of high-performance TMPs for hydrogen evolution are systematically summarized. On this basis, in order to achieve large-scale hydrogen production in industry, the hydrogen evolution performance and stability of TMPs at a high current density are also discussed. Peculiarly, the practical application and requirements in proton exchange membrane (PEM) or anion exchange membrane (AEM) electrolyzers can guide the advanced design of regulatory strategies of TMPs for green hydrogen production from renewable energy. Finally, the challenges and prospects in the future development trend of TMPs for efficient and industrial water electrolysis are given.

Photothermoelectric Synergistic Hydrovoltaic Effect: A Flexible Photothermoelectric Yarn Panel for Multiple Renewable-Energy Harvesting

The human body is in a complex environment affected by body heat, light, and sweat, requiring the development of a wearable multifunctional textile for human utilization. Meanwhile, the traditional thermoelectric yarn is limited by expensive and scarce inorganic thermoelectric materials, which restricts the development of thermoelectric textiles. Therefore, in this paper, photothermoelectric yarns (PPDA-PPy-PEDOT/CuI) using organic poly(3,4-ethylenedioxythiophene) (PEDOT) and inorganic thermoelectric material cuprous iodide (CuI) are used for the thermoelectric layer and poly(pyrrole) (PPy) for the light-absorbing layer. With the introduction of PPy, the temperature difference of the photothermoelectric yarn can be increased for a better voltage output. Subsequently synergizing the photothermoelectric effect with the hydrovoltaic effect to create higher electric potentials, a single wet photothermoelectric yarn obtained by preparation can be irradiated under an infrared lamp at a voltage of up to 0.47 V. Finally, the photothermoelectric yarn PPDA-PPy-PEDOT/CuI was assembled in a series and parallel to obtain a photothermoelectric yarn panel, which was able to output 41.19 mV under an infrared lamp, and the synergistic photothermoelectric and hydrovoltaic effects of the photothermoelectric panel were tested outdoors on human body, and we found that the voltage was able to reach approximately 0.16 V under sunlight. Therefore, the voltage values obtained from the photothermoelectric yarns in this study are competitive and provide a new research idea for the study of photothermoelectric yarns.

Recent Advances in Carbon-Based Electrodes for Energy Storage and Conversion

Carbon-based nanomaterials, including graphene, fullerenes, and carbon nanotubes, are attracting significant attention as promising materials for next-generation energy storage and conversion applications. They possess unique physicochemical properties, such as structural stability and flexibility, high porosity, and tunable physicochemical features, which render them well suited in these hot research fields. Technological advances at atomic and electronic levels are crucial for developing more efficient and durable devices. This comprehensive review provides a state-of-the-art overview of these advanced carbon-based nanomaterials for various energy storage and conversion applications, focusing on supercapacitors, lithium as well as sodium-ion batteries, and hydrogen evolution reactions. Particular emphasis is placed on the strategies employed to enhance performance through nonmetallic elemental doping of N, B, S, and P in either individual doping or codoping, as well as structural modifications such as the creation of defect sites, edge functionalization, and inter-layer distance manipulation, aiming to provide the general guidelines for designing these devices by the above approaches to achieve optimal performance. Furthermore, this review delves into the challenges and future prospects for the advancement of carbon-based electrodes in energy storage and conversion.

Zn and Ni dual hydrogen evolution sites integrated onto CdS for effective photocatalytic hydrogen production

Effective and affordable photocatalysts play an important role in the cost reduction of solar hydrogen production through photocatalytic water splitting. In this research, a Zn²⁺ and Ni²⁺ modified carbon hydrogen evolution cocatalyst (ZnNi-C) were synthesized and immobilized onto the surface of CdS (CdS@ZnNi-C) for photocatalytic hydrogen evolution (PHE). The preparation used an ethylenediaminetetraacetic acid disodium (EDTA)-assisted method. The hydrogen evolution rate and apparent quantum efficiency (AQE) at 420 nm for an optimized CdS@ZnNi-C photocatalyst are15.7 mmol/h/g and 31.4 %, respectively. The rate is 2.4 times and 3.7 times greater than those of Zn²⁺ and Ni²⁺ modified carbon cocatalysts (Zn-C) and (Ni-C) on CdS (CdS@Zn-C) and (CdS@Ni-C), respectively. Density functional theory calculations indicate that the elevated catalytic performance of CdS@ZnNi-C is due to the co-anchored Zn²⁺ and Ni²⁺ in carbon layers that lead to a favorable Gibbs free energy (ΔG_H*) for hydrogen evolution. This approach is valuable for the design of stable and efficient photocatalysts for renewable hydrogen production.

Strain engineering of electrocatalysts for hydrogen evolution reaction

As the key half reaction of water-splitting electrolysis, the hydrogen evolution reaction (HER) that occurs at the cathode directly determines the overall efficiency of hydrogen production. To improve the efficiency of electrochemical water splitting for hydrogen generation, efficient and robust catalysts need to be developed. Strain engineering, which represents an effective and promising category of strategies, can regulate the electronic structures of catalysts by modulating the lattice strain and ultimately optimizing the HER dynamics. This work critically reviews the recent progress of strain engineering in HER and provides future perspectives for this area. The methods and characterization techniques are also introduced in detail. Hopefully this review can provide guidelines for the design and manufacturing of advanced catalysts for HER and other heterogeneous catalysis reactions such as chemical sensing, CO₂ reduction and NH₃ synthesis.

Biomimicry-inspired fish scale-like Ni3N/FeNi3N/NF superhydrophilic/superaerophobic nanoarrays displaying high electrocatalytic performance

The mass transfer efficiency and structural stability of the electrode are critical for industrialized water electrolysis operations. Herein, the biomimicry-inspired design of Ni₃N/FeNi₃N/NF nanoarrays with a fish scale-like structure, which endowed the Ni₃N/FeNi₃N/NF nanoarrays with rapid infiltration of aqueous solution within 60 ms and 169° bubble contact angle, is demonstrated. The optimal Ni₃N/FeNi₃N/NF sample displayed catalytic activity with hydrogen evolution reaction (HER) overpotentials of only 48 mV at 10 mA cm^-2 and 102 mV at 100 mA cm^-2. Similarly, the overpotential of the anodic-coupled urea oxidation reaction (UOR) was only 1.3 V at 10 mA cm^-2 and 1.35 V at 100 mA cm^-2. Besides, the small impact resulting from the rapid bubble extraction within the Ni₃N/FeNi₃N/NF nanoarrays ensured excellent HER cycling stability over 100 h at a current density of 50 mA cm^-2. The further scale-up experiment suggests the industrialization prospects of the prepared Ni₃N/FeNi₃N/NF electrocatalysts.

In Situ Surface Reconstruction of Catalysts for Enhanced Hydrogen Evolution

The in situ surface reconstitution of a catalyst for hydrogen evolution refers to its structure evolution induced by strong interactions with reaction intermediates during the hydrogen evolution reaction (HER), which eventually leads to the self-optimization of active sites. In consideration of the superior performance that can be achieved by in situ surface reconstitution, more and more attention has been paid to the relationship between active site structure evolution and the self-optimization of HER activity. More and more in situ and/or operando techniques have been explored to track the dynamic structural evolution of HER catalysts in order to clarify the underlying mechanism. This review summarizes recent advances in various types of reconstruction such as the reconfiguration of crystallinity, morphological evolution, chemical composition evolution, phase transition refactoring, surface defects, and interface refactoring in the HER process. Finally, different perspectives and outlooks are offered to guide future investigations. This review is expected to provide some new clues for a deeper understanding of in situ surface reconfiguration in hydrogen evolution reactions and the targeted design of catalysts with desirable structures.

Complementary combinative strategy of defect engineering and graphene coupling for efficient energy-functional materials

The synergetic combination of defect engineering and graphene coupling enables to develop an effective way of exploring efficient bifunctional electrocatalyst/electrode materials. Defect-engineered amorphous MoO₂ -reduced graphene oxide (rGO) nanohybrid was synthesized by soft-chemical reduction of K₂ MoO₄ in graphene oxide colloids. Mo K-edge X-ray absorption spectroscopy clearly demonstrates the rutile-type local atomic structure of amorphous MoO₂ with significant oxygen vacancies and intimate electronic coupling with rGO. The defect-introduced MoO₂ -rGO nanohybrid shows excellent bifunctionality as electrocatalyst for hydrogen evolution reaction and electrode for sodium-ion batteries, which are superior to those of crystalline MoO₂ -rGO homologue. The beneficial effect of simultaneous defect control and rGO coupling can be ascribed to the provision of oxygen vacancies acting as active sites, the increase of electrical conductivity, and the improvement of reaction kinetics.

Modulation of electronic structures in two-dimensional electrocatalysts for the hydrogen evolution reaction

The electrocatalytic hydrogen evolution reaction (HER) has attracted substantial attention owing to its important role in realizing economic and sustainable hydrogen production via water electrolysis. Designing two-dimensional (2D) materials with large surface area, highly exposed surface sites and facile charge transport pathways is highly attractive for promoting the HER activity of the earth-abundant catalysts, and conducting rational modulations in the electronic structures is considered to be promising in further optimizing the intrinsic HER activity and thus realizing promoted HER performance. In this Feature Article, we systematically summarize recent progress in the modulation of the electronic structures of 2D HER electrocatalysts via multiple strategies including elemental doping, formation of alloyed structures, defect engineering, facet engineering, phase regulation, interface engineering and hybridization of the nanocatalysts with 2D substrates, and discuss the role of electronic structures in optimizing the intrinsic HER activity of 2D HER catalysts. We anticipate that this Feature Article will offer helpful guidance for oriented design and optimization of efficient electrocatalysts for scalable and economic hydrogen production.

Graphene Supported MoS2 Structures with High Defect Density for an Efficient HER Electrocatalysts

The development of novel efficient and robust electrocatalysts with sufficient active sites is one of the key parameters for hydrogen evolution reactions (HER) catalysis, which plays a key role in hydrogen production for clean energy harvesting. Recently, two-dimensional (2D) materials, especially those based upon transition metal dichalcogenides such as molybdenum disulfide (MoS₂), have gained attention for the catalysis of hydrogen production because of their exceptional properties. Innovative strategies have been developed to engineer these material systems for improvements in their catalytic activity. Toward this aim, the facile growth of MoS₂ clusters by sulfurization of molybdenum dioxide (MoO₂) particles supported on reduced graphene oxide (rGO) foams using the chemical vapor deposition (CVD) method is reported. This approach created various morphologies of MoS₂ with large edges and defect densities on the basal plane of rGO supported MoS₂ structures, which are considered as active sites for HER catalysis. In addition, MoS₂ nanostructures on the surface of the porous rGO network show robust physical interactions, such as van der Waals and π-π interactions between MoS₂ and rGO. These features result in an improved process to yield a suitable HER catalyst. In order to gain a better understanding of the improvement of this MoS₂-based HER catalyst, fully atomistic molecular dynamics (MD) simulations of different defect geometries were also performed.

Defect engineering in two-dimensional electrocatalysts for hydrogen evolution

The electrocatalytic hydrogen evolution reaction (HER) is an efficient and economic pathway to generate clean hydrogen energy in a sustainable manner. To improve the HER activity of Earth-abundant catalysts, reducing the dimension of materials is an effective strategy, and in this context two-dimensional (2D) materials have received substantial research attention owing to their large surface area and 2D charge transport channels. However, the thermodynamically stable basal surface of 2D catalysts is usually inactive in catalysis, which significantly impedes further optimization of the 2D HER catalysts. In this Minireview, we highlight in detail that defect engineering in 2D catalysts could bring multiple benefits in improving the HER activity. From the point of view of kinetics, defect sites could serve as active sites for catalyzing the HER process directly, and the introduction of defect structures may result in the optimization of electronic structures of the catalysts, thereby facilitating the HER process. Besides, for catalytically inert substrate materials, the defect sites could act as anchoring sites for catalyst loading, thus realizing efficient HER performance with the aid of enhanced electric conductivity. We anticipated that this Minireview could provide useful guidance for designing advanced HER catalysts in the future.

In situ modulation of silica-supported MoO2/Mo2C heterojunction for enhanced hydrogen evolution reaction

Hydrogen being a promising source of clean energy, the production of hydrogen using electrocatalysis and the development of carbon-neutral energy conversion technologies are crucial.