Bimetallic Nanoalloy Catalysts for Green Energy Production: Advances in Synthesis Routes and Characterization Techniques

Bimetallic Nanoalloy catalysts have diverse uses in clean energy, sensing, catalysis, biomedicine, and energy storage, with some supported and unsupported catalysts. Conventional synthetic methods for producing bimetallic alloy nanoparticles often produce unalloyed and bulky particles that do not exhibit desired characteristics. Alloys, when prepared with advanced nanoscale methods, give higher surface area, activity, and selectivity than individual metals due to changes in their electronic properties and reduced size. This review demonstrates the synthesis methods and principles to produce and characterize highly dispersed, well-alloyed bimetallic nanoalloy particles in relatively simple, effective, and generalized approaches and the overall existence of conventional synthetic methods with modifications to prepare bimetallic alloy catalysts. The basic concepts and mechanistic understanding are represented with purposely selected examples. Herein, the enthralling properties with widespread applications of nanoalloy catalysts in heterogeneous catalysis are also presented, especially for Hydrogen Evolution Reaction (HER), Oxidation Reduction Reaction (ORR), Oxygen Evolution Reaction (OER), and alcohol oxidation with a particular focus on Pt and Pd-based bimetallic nanoalloys and their numerous fields of applications. The high entropy alloy is described as a complicated subject with an emphasis on laser-based green synthesis of nanoparticles and, in conclusion, the forecasts and contemporary challenges for the controlled synthesis of nanoalloys are addressed.

Noble metal nanodendrites: growth mechanisms, synthesis strategies and applications

Inorganic nanodendrites (NDs) have become a kind of advanced nanomaterials with broad application prospects because of their unique branched architecture. The structural characteristics of nanodendrites include highly branched morphology, abundant tips/edges and high-index crystal planes, and a high atomic utilization rate, which give them great potential for usage in the fields of electrocatalysis, sensing, and therapeutics. Therefore, the rational design and controlled synthesis of inorganic (especially noble metals) nanodendrites have attracted widespread attention nowadays. The development of synthesis strategies and characterization methodology provides unprecedented opportunities for the preparation of abundant nanodendrites with interesting crystallographic structures, morphologies, and application performances. In this review, we systematically summarize the formation mechanisms of noble metal nanodendrites reported in recent years, with a special focus on surfactant-mediated mechanisms. Some typical examples obtained by innovative synthetic methods are then highlighted and recent advances in the application of noble metal nanodendrites are carefully discussed. Finally, we conclude and present the prospects for the future development of nanodendrites. This review helps to deeply understand the synthesis and application of noble metal nanodendrites and may provide some inspiration to develop novel functional nanomaterials (especially electrocatalysts) with enhanced performance.

Compositional dependence of structures and hydrogen evolution reaction activity of platinum-group-metal quinary RuRhPdIrPt alloy nanoparticles

Platinum-group-metal quinary RuRhPdIrPt alloy nanoparticles were synthesised with compositions slightly away from equimolar, and their crystal and electronic structures were investigated. Their lattice constant changed linearly with composition, while the d-band centre changed nonlinearly. Their catalytic activities for the hydrogen evolution reaction were not correlated with their d-band centre.

Solid-state synthesis of CdFe2O4 binary catalyst for potential application in renewable hydrogen fuel generation

Clean energy is highly needed at this time when the energy requirements are rapidly increasing. The observed increasing energy requirement are largely due to continued industrialization and global population explosion. The current means of energy source is not sustainable because of several reasons, most importantly, environmental pollution and human health deterioration due to burning of fossil fuels. Therefore, this study develops a new catalyst for hydrogen and oxygen evolution by water splitting as a potential energy vector. The binary metal oxide catalyst CdFe₂O₄ was synthesized by the solventless solid-mechanical alloying method. The as-prepared catalyst was well characterized by several methods including field emission scanning electron microscopy (FESEM), X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), Fourier Transform infrared red spectroscopy (FTIR), energy dispersive X-ray spectroscopy (XEDS). The as-prepared catalyst, CdFe₂O₄ was successfully applied for water electrolysis at a moderate overpotential (470 mV). Specifically, the onset potential for the oxygen and hydrogen evolution reactions (OER and HER) were 1.6 V_/RHE and 0.2 V_/RHE respectively (vs. the reversible hydrogen electrode). The electrode potential required to reach 10 mA/cm^-2 for OER (in alkaline medium) and HER (in acidic medium) was 1.70 V_/RHE (corresponding to overpotential η = 0.47 and − 0.30 V_/RHE (η = − 0.30 V) respectively. Similarly, the developed OER and HER catalyst displayed high current and potential stability for a period of 12 h. This approach is seen as the right track of making water electrolysis for hydrogen energy feasible through provision of low-energy requirement for the electrolytic process. Therefore, CdFe₂O₄ is a potential water splitting catalyst for hydrogen evolution which is a clean fuel and an antidote for world dependence on fossil fuel for energy generation.

Recent Advances in Layered-Double-Hydroxides Based Noble Metal Nanoparticles Efficient Electrocatalysts

With the energy crisis and environmental pollution becoming more and more serious, it is urgent to develop renewable and clean energy. Hydrogen production from electrolyzed water is of great significance to solve the energy crisis and environmental problems in the future. Recently, layered double hydroxides (LDHs) materials have been widely studied in the electrocatalysis field, due to their unique layered structure, tunable metal species and highly dispersed active sites. Moreover, the LDHs supporting noble metal catalysts obtained through the topotactic transformation of LDHs precursors significantly reduce the energy barrier of electrolyzing water, showing remarkable catalytic activity, good conductivity and excellent durability. In this review, we give an overview of recent advances on LDHs supporting noble metal catalysts, from a brief introduction, to their preparation and modification methods, to an overview of their application in the electrocatalysis field, as well as the challenges and outlooks in this promising field on the basis of current development.

Ruthenium nanodendrites on reduced graphene oxide: an efficient water and 4-nitrophenol reduction catalyst

A green and efficient protocol is reported for the elegant design of reduced graphene oxide (rGO)-supported Ru nanodendrites for promotion of electrochemical water reduction in a wide pH range as well as for environmental remediation.

Cyanogroup functionalized sub-2 nm ultrafine Pt nanonetworks reinforce electrocatalytic hydrogen evolution in a broad pH range

Cyanogroup functionalized Pt ultrafine nanonetworks are synthesized via a facile one-pot oil bath heating method, and exhibit excellent HER performance in a broad pH range.