N-Doped Mo2C Nanobelts/Graphene Nanosheets Bonded with Hydroxy Nanocellulose as Flexible and Editable Electrode for Hydrogen Evolution Reaction

Advances in Cellulose-Based Composites for Energy Applications

The various forms of cellulose-based materials possess high mechanical and thermal stabilities, as well as three-dimensional open network structures with high aspect ratios capable of incorporating other materials to produce composites for a wide range of applications. Being the most prevalent natural biopolymer on the Earth, cellulose has been used as a renewable replacement for many plastic and metal substrates, in order to diminish pollutant residues in the environment. As a result, the design and development of green technological applications of cellulose and its derivatives has become a key principle of ecological sustainability. Recently, cellulose-based mesoporous structures, flexible thin films, fibers, and three-dimensional networks have been developed for use as substrates in which conductive materials can be loaded for a wide range of energy conversion and energy conservation applications. The present article provides an overview of the recent advancements in the preparation of cellulose-based composites synthesized by combining metal/semiconductor nanoparticles, organic polymers, and metal-organic frameworks with cellulose. To begin, a brief review of cellulosic materials is given, with emphasis on their properties and processing methods. Further sections focus on the integration of cellulose-based flexible substrates or three-dimensional structures into energy conversion devices, such as photovoltaic solar cells, triboelectric generators, piezoelectric generators, thermoelectric generators, as well as sensors. The review also highlights the uses of cellulose-based composites in the separators, electrolytes, binders, and electrodes of energy conservation devices such as lithium-ion batteries. Moreover, the use of cellulose-based electrodes in water splitting for hydrogen generation is discussed. In the final section, we propose the underlying challenges and outlook for the field of cellulose-based composite materials.

Ni-Directed biphase N-doped Mo2C as an efficient hydrogen evolution catalyst in both acidic and alkaline conditions

The development of efficient and low-cost catalysts is of great significance for the future application of the electrocatalytic hydrogen evolution reaction (HER). Herein, a series of Ni,N co-doped Mo₂C nanostructures (Ni_x-Mo₂C/N) with different Ni content levels are fabricated. The phase-directing effect of Ni on Mo₂C/N is observed, which is in charge of the phase transformation of Mo₂C/N from an α- to a β-phase. At the optimized Ni-doping level, biphase Ni₁₅-Mo₂C/N exhibits outstanding HER activity under both acidic and alkaline conditions. In particular, under alkaline conditions, Ni₁₅-Mo₂C/N delivers an overpotential of only 105.0 mV, accompanied by a low Tafel slope of 44.96 mV dec^-1. The performance is comparable to commercial 20% Pt/C and higher than most state-of-the-art Mo₂C-based catalysts as well.

An efficient factor for fast screening of high-performance two-dimensional metal-organic frameworks towards catalyzing oxygen evolution reaction

Two-dimensional (2D) Metal-Organic frameworks (MOFs) are promising materials for catalyzing oxygen evolution reaction (OER) due to abundant exposed active sites and high specific surface area. However, how to fast screen...

Atomically Dispersed Mo Sites Anchored on Multichannel Carbon Nanofibers toward Superior Electrocatalytic Hydrogen Evolution

Developing affordable and efficient electrocatalysts as precious metal alternatives toward the hydrogen evolution reaction (HER) is crucially essential for the substantial progress of sustainable H₂ energy-related technologies. The dual manipulation of coordination chemistry and geometric configuration for single-atom catalysts (SACs) has emerged as a powerful strategy to surmount the thermodynamic and kinetic dilemmas for high-efficiency electrocatalysis. We herein rationally designed N-doped multichannel carbon nanofibers supporting atomically dispersed Mo sites coordinated with C, N, and O triple components (labeled as Mo@NMCNFs hereafter) as a superior HER electrocatalyst. Systematic characterizations revealed that the local coordination microenvironment of Mo is determined to be a Mo-O₁N₁C₂ moiety, which was theoretically probed to be the energetically favorable configuration for H intermediate adsorption by density functional theory calculations. Structurally, the multichannel porous carbon nanofibers with open ends could effectively enlarge the exposure of active sites, facilitate mass diffusion/charge transfer, and accelerate H₂ release, leading to promoted reaction kinetics. Consequently, the optimized Mo@NMCNFs exhibited superior Pt-like HER performance in 0.5 M H₂SO₄ electrolyte with an overpotential of 66 mV at 10 mA cm^-2, a Tafel slope of 48.9 mV dec^-1, and excellent stability, outperforming a vast majority of the previously reported nonprecious HER electrocatalysts. The concept of both geometric and electronic engineering of SACs in this work may provide guidance for the design of high-efficiency molecule-like heterogeneous catalysts for a myriad of energy technologies.

Laser ablation in air and its application in catalytic water splitting and Li-ion battery

Pulse laser has been widely used in both fundamental science and practical technologies. In this perspective, we highlight the employment of pulse laser ablation in air (LAA) in energy-related catalytic reactions. With LAA, samples are directly ablated in ambient air, which makes this technology facile to conduct. Materials can be modified by LAA in multiple aspects, such as morphology modulation, heterojunction fabrication, or defects engineering, which are desired features for energy-related catalytic reactions. We begin this perspective with a brief introduction of this technology, including the mechanism, the experimental setup, and the characteristic of laser-ablated materials. The recent works utilizing LAA are then summarized to prove the promising prospects of LAA in the energy field. Finally, several opportunities about the future usage of LAA are proposed and discussed.

Non-thermal radiation heating synthesis of nanomaterials

The nanoscale effect enables the unique magnetic, optical, thermal and electrical properties of nanostructured materials and has attracted extensive investigation for applications in catalysis, biomedicine, sensors, and energy storage and conversion. The widely used synthesis methods, such as traditional hydrothermal reaction and calcination, are bulk heating processes based on thermal radiation. Differing from traditional heating methods, non-thermal radiation heating technique is a local heating mode. In this regard, this review summarizes various non-thermal radiation heating methods for synthesis of nanomaterials, including microwave heating, induction heating, Joule heating, laser heating and electron beam heating. The advantages and disadvantages of these non-thermal radiation heating methods for the synthesis of nanomaterials are compared and discussed. Finally, the future development and challenges of non-thermal radiation heating method for potential synthesis of nanomaterials are discussed.

Biomass-Derived Bilayer Solar Evaporator with Enhanced Energy Utilization for High-Efficiency Water Generation

Solar-driven evaporation has been recognized as a promising approach to address global crises of drinking water via virtue of abundant and green solar energy. However, a great challenge still exists for achieving efficient usage of solar energy combined with fast water evaporation. Here, a double-structural solar evaporator consists of an upper copper sulfide (CuS) agar-based aerogel and a bottom molybdenum carbide/carbon (MoCC) composite of cotton fibers-derived aerogel (CuSAA/MoCCFA), which is constructed for solar evaporation. The CuS layer performs as a solar-thermal converter with efficient light adsorption and prominent thermally localized ability, while the bottom layer (superhydrophilic porous aerogel) guarantees sufficient water transportation and excellent thermal insulation. The fully integrative solar evaporator has an attractive water evaporation rate of 2.44 kg m^-2 h^-1 with a superb solar-thermal conversion efficiency of 92.77% under 1 sun illumination. More notably, the bilayer aerogel exhibits long-term durability in high-salinity media during solar-driven desalination. In addition, a solar absorber assisted with low-temperature phase change materials comprise the solar evaporation system, which is aimed at solar-thermal energy storage and reutilization for conquering solar intermittence. Such superior performance of a comprehensive solar desalination system provides a new avenue for highly efficient and suitable clean water production under natural sunlight conditions.

Charge Redistribution Caused by S,P Synergistically Active Ru Endows an Ultrahigh Hydrogen Evolution Activity of S-Doped RuP Embedded in N,P,S-Doped Carbon

Water splitting for production of hydrogen as a clean energy alternative to fossil fuel has received much attention, but it is still a tough challenge to synthesize electrocatalysts with controllable bonding and charge distribution. In this work, ultrafine S-doped RuP nanoparticles homogeneously embedded in a N, P, and S-codoped carbon sheet (S-RuP@NPSC) is synthesized by pyrolysis of poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol) (PZS) as the source of C/N/S/P. The bondings between Ru and N, P, S in PZS are regulated to synthesize RuS2 (800 °C) and S-RuP (900 °C) by different calcination temperatures. The S-RuP@NPSC with low Ru loading of 0.8 wt% with abundant active catalytic sites possesses high utilization of Ru, the mass catalytic activity is 22.88 times than 20 wt% Pt/C with the overpotential of 250 mV. Density functional theory calculation confirms that the surface Ru (-0.18 eV) and P (0.05 eV) are catalytic active sites for the hydrogen evolution reaction (HER), and the according charge redistribution of Ru is regulated by S and P with reverse electronegativity and electron-donor property to induce a synergistically enhanced reactivity toward the HER. This work provides a rational method to regulate the bonding and charge distribution of Ru-based electrocatalysts by reacting macromolecules with multielement of C/N/S/P with Ru.

Phosphorus-Doped Iron Nitride Nanoparticles Encapsulated by Nitrogen-Doped Carbon Nanosheets on Iron Foam In Situ Derived from Saccharomycetes Cerevisiae for Electrocatalytic Overall Water Splitting

It is vitally essential to propose a novel, economical, and safe preparation method to design highly efficient electrocatalysts. Herein, phosphorus-doped iron nitride nanoparticles encapsulated by nitrogen-doped carbon nanosheets are grown directly on the iron foam substrate (P-Fe₃ N@NC NSs/IF) by in situ deriving from Saccharomycetes cerevisiae (S. cerevisiae), where anion elements of C, N, and P all from S. cerevisiae replace the hazardous CH₄ , NH₃ , and H₃ P. The diffusion pattern of N, P in S. cerevisiae and contact form between metal and S. cerevisiae observably affect the composition and phase of the product during high-temperature calcination. The obtained P-Fe₃ N@NC NSs/IF demonstrates superior electrocatalytic performance for the hydrogen evolution reaction and oxygen evolution reaction, also satisfying durability. Theoretical calculation confirms that Fe sites of P-Fe₃ N serve as the active center, and N sites and P doping regulate the hydrogen binding strength to enhance catalytic ability. Additionally, the two-electrode electrolyzer assembled by P-Fe₃ N@NC NSs/IF as both anode and cathode electrodes needs only 1.61 V to reach 10 mA cm^-2 for overall water splitting with a superb stability. The S. cerevisiae-based process presents a feasible approach for synthesis of nitrides, carbides, phosphides, and electrocatalytic applications.

Applications of Nanocellulose/Nanocarbon Composites: Focus on Biotechnology and Medicine

Nanocellulose/nanocarbon composites are newly emerging smart hybrid materials containing cellulose nanoparticles, such as nanofibrils and nanocrystals, and carbon nanoparticles, such as "classical" carbon allotropes (fullerenes, graphene, nanotubes and nanodiamonds), or other carbon nanostructures (carbon nanofibers, carbon quantum dots, activated carbon and carbon black). The nanocellulose component acts as a dispersing agent and homogeneously distributes the carbon nanoparticles in an aqueous environment. Nanocellulose/nanocarbon composites can be prepared with many advantageous properties, such as high mechanical strength, flexibility, stretchability, tunable thermal and electrical conductivity, tunable optical transparency, photodynamic and photothermal activity, nanoporous character and high adsorption capacity. They are therefore promising for a wide range of industrial applications, such as energy generation, storage and conversion, water purification, food packaging, construction of fire retardants and shape memory devices. They also hold great promise for biomedical applications, such as radical scavenging, photodynamic and photothermal therapy of tumors and microbial infections, drug delivery, biosensorics, isolation of various biomolecules, electrical stimulation of damaged tissues (e.g., cardiac, neural), neural and bone tissue engineering, engineering of blood vessels and advanced wound dressing, e.g., with antimicrobial and antitumor activity. However, the potential cytotoxicity and immunogenicity of the composites and their components must also be taken into account.