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A facile three-step approach for tubular CoP preparation and its catalytic activity for HER and OER are reported. The CoP microtubes show superior HER performance in a wide pH range with low overpotentials of 91, 101 and 113 mV at 10 mA cm−2 in 0.5 M H2SO4, 1 M KOH and 1 M PBS, respectively. Additionally, it also depicts superior OER performance with an overpotential of 300 mV at 10 mA cm−2, which is lower than reported precious metal oxides. The improved electrocatalytic performance of tubular CoP is likely attributed to the porous tube-like structural features, which not only afford rich exposed active sites, but also accelerate the charge or mass transfer efficiency, and thus efficiently promote the HER performance. The synthesis of tubular CoP confirms the importance of morphology features and provides a new insight to rationally design and synthesize highly effective non-noble metal phosphide-based pH-universal electrocatalysts for HER.

Proton exchange membrane (PEM) water electrolyzers are a key technology in decarbonizing hydrogen production. Though the market for PEM electrolyzer systems is growing, there are concerns that the ...

Maximizing atomic utilization of precious metal-based catalysts is of great significance in heterogeneous catalysis, also becoming a useful strategy to develop efficient electrocatalysts for hydrog...

The design and development of strategies and catalysts are essential for sustainable energy production, particularly for the hydrogen evolution reaction (HER). Precious Pt/C catalyst is known to de...

The key challenge for scalable production of hydrogen from water lies in the rational design and preparation of high-performance and earth-abundant electrocatalysts to replace precious metal Pt and IrO2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Although atomic M-N-C materials have been extensively studied in heterogeneous catalysis field, the insufficient antioxidant capacity of carbonous substrates hinders their practical application in OER. Developing highly active and stable OER electrocatalysts is the key for electrochemical water splitting. This review presents feasible design strategies for fabricating carbon-free single-site catalysts and their applications in HER/OER and overall water splitting. The constitutive relationships between structure, composition, and catalytic performance for HER and OER are detailly discussed, providing ponderable insights into rationally constructing high-performance HER and OER electrocatalysts. The perspectives on the challenges and future research orientations in single-site catalysts for electrochemical water splitting are suggested.

The first-row transition metal catalysis often serves as a complementary strategy to traditional precious metal catalysis. Other than their advantages in abundance and sustainability, their unique electronic properties often give rise to more complicated reactivities. Co-catalyzed hydrogenation is an example of these relatively underexplored first-row transition metal catalysis. In this work, we will focus on an example of Co-catalyzed hydrogenation, which was reported to be able to selectively hydrogenate C=C but not C=O. We have performed DFT calculations on the model reactions, accompanied by a series of structure and bonding analysis, to investigate the underlying reason for the observed selectivity. We have identified the predominant σ-donating nature of phosphine and the π-accepting nature of C=C/C=O fragments upon interaction with Co(I) center, and we have also analyzed why these differences would lead to different coordination geometry, stability, and reactivity. We anticipate that all these analyses would advance our understanding in Co(I) catalysis and are beneficial for future Co-based catalyst design.

Electrocatalytic water splitting for hydrogen production plays a vital role in the development of new energy field, but there is still a lack of low-content precious metal or cost-effective non-noble metal catalysts for the hydrogen evolution reaction (HER). Therefore, how to develop the catalysts with a smaller amount of precious metal to achieve higher performance is still a major challenge. Herein, we have fabricated Ru–Ni2P@Ni(OH)2/NF-2 heterostructure by phosphating Ni(OH)2/NF and then anchoring Ru on the surface through wet chemical strategy. Benefiting from its optimal ΔGH∗ and synergistic effect, this Ru–Ni2P@Ni(OH)2/NF-2 catalyst shows superior electrocatalytic HER kinetics in alkaline electrolyte. A small overpotential of 31 mV is needed for this electrocatalyst to obtain the current densities of 10 mA cm−2 with remarkable durability over 24 h. This work provides a new strategy for the preparation of effective HER electrocatalyst with a low precious metal content.

Electrochemical water splitting for hydrogen production has sparked intensive interests because it provides a new approach for sustainable energy resources and the avoidance of environmental problems. The precious metal‐based single atomic catalysts (PMSACs) have been widely employed in water splitting catalysis by virtue of their maximum atom utilization and unique electronic structure, which can reduce metal amounts and remain high catalytic performance simultaneously. In this review, we will summarize recent research efforts toward developing SACs based on precious metals with excellent performance for electrochemical water splitting catalysis. First, the synthesis strategies for PMSACs will be classified and introduced including high‐temperature pyrolysis, electrochemical method, photochemical reduction, wet chemistry method, etc. Then, a short description of characterization techniques for SACs will be given, which mainly involves the aberration‐corrected scanning‐transmission electron microscopy (AC‐STEM) and X‐ray absorption spectroscopy (XAS). In particular, the relationship between the electronic structure of the precious metal atomic sites and performance for water splitting will be discussed according to the theoretical and experimental results. Finally, a brief perspective will be provided to highlight the challenges and opportunities for the development of novel PMSACs suitable for electrochemical water splitting applications.

Electrooxidation of NH3 has gained extensive attention for energy and environmental applications such as fuel cells and water purification. Pt-based precious metal alloy catalysts have been intensi...

Manganese complexes have been considered as a cheap and readily available alternative to commonly used precious metal catalysts in C–C bond coupling reactions. Although high-valent Mn aryl intermediates have been proposed in such reactions, a mechanistic understanding of possible organometallic intermediates in Mn-mediated C–C coupling is still lacking due to their high reactivity. We report the synthesis of stable, isolable Mn(III) aryl complexes obtained by oxidative addition of aryl bromide or aryl chloride. These complexes react with a range of organometallic alkylating or arylating reagents (alkyl and aryl Grignard reagents, MeLi, ZnMe2) to undergo C(sp2)–C(sp3) or C(sp2)–C(sp2) bond coupling, and a preliminary catalytic system could be demonstrated. The reagent scope and yield of the C(sp2)–C(sp3) coupled product can further be increased by addition of TEMPO as an oxidant, generating alkyl radicals.

Developing alternatives to noble-metal-based catalysts toward the oxygen reduction reaction (ORR) process plays a key role in the application of low-temperature fuel cells. Carbon-based, precious-metal-free electrocatalysts are of great interest due to their low cost, abundant sources, active catalytic performance, and long-term stability. They are also supposed to feature intrinsically high activity and highly dense catalytic sites along with their sufficient exposure, high conductivity, and high chemical stability, as well as effective mass transfer pathways. In this Review, we focus on carbon-based, precious-metal-free nanocatalysts with synergistic modulation of active-site species and their exposure, mass transfer, and charge transport during the electrochemical process. With this knowledge, perspectives on synergistic modulation strategies are proposed to push forward the development of Pt-free ORR catalysts and the wide application of fuel cells.

In this article, we describe the development of a new aerobic C–H oxidation methodology catalyzed by a precious metal-free LaMnO3 perovskite catalyst. Molecular oxygen is used as the sole oxidant in this approach, obviating the need for other expensive and/or environmentally hazardous stoichiometric oxidants. The electronic and structural properties of the LaMnO3 catalysts were systematically optimized, and a reductive pretreatment protocol was proved to be essential for acquiring the observed high catalytic activities. It is demonstrated that this newly developed method was extremely effective for the oxidation of alkylarenes to ketones as well as for the oxidative dimerization of 2-naphthol to 1,1-binaphthyl-2,2-diol (BINOL), a particularly important scaffold for asymmetric catalysis. Detailed spectroscopic and mechanistic studies provided valuable insights into the structural aspects of the active catalyst and the reaction mechanism.

Transition metal-based catalysts are the next most efficient catalysts for hydrogen generation in alkaline media, after Pt-group metal catalysts. Research employing transition metal-based catalysts has progressed exponentially in recent years, resulting in catalysts with excellent activity and stability. Compared to other neighbour d-metals (Ni, Fe, Co, Cu) which receive proper preference, research on Zn, Mn, and Cr containing electrocatalysts for water electrolysis is limited. Chromium in general has received limited consideration but has begun to attract the attention of researchers in the past few years. This review provides a brief discussion and evaluation of different catalysts (oxides, hydroxides, nitrides, phosphides, sulphides, carbides, etc.) incorporating different phases of the Cr component, together with a perspective on the catalytic significance of using Cr as a co-catalyst for hydrogen evolution in alkaline media. With advancements in catalysis research, electroactivity and stability showcased by Cr-based catalysts, some even competitive against precious metal catalysts, can be lucrative solutions for H2 generation.

Hydrogen generation via water electroreduction is pivotal for exploiting clean-energy skills. Nevertheless, developing a low price and high-performance catalytic activity substance to take the place of expensive precious metal currently in use is still a precedent condition for technology commercialization. In this study, large-scale hierarchical few-layer MoSe2 nanosheets were successfully grown on the surface of sodium sulfide crystals. The water solubility of sodium sulfide makes it advantageous to generate MoSe2 nanolayers via a simple and inexpensive means. The micron-level sodium sulfide crystal surface has a very critical function in the nucleus formation and development of few-layer MoSe2. The ultrathin hierarchical MoSe2 nanolayers obtained using the proposed approach have preferable hydrogen evolution reaction. Furthermore, it is a fascinating technique that the template can be reused without environmental pollution. This research can be used to manufacture other ultrathin hierarchical transition-metal dichalcogenide nanolayers for high-performance many-sided applications.

(Ce,Zr,La)O2-Supported Pt, Pd and Pt–Pd bimetallic catalysts for NOx, HC and CO elimination were synthesized. It is found that the Pt–Pd bimetallic catalysts all exhibit an atomic-level alloy structure, and the surplus precious metals are present as isolated PMOx (precious metal oxides) species on the Pt–Pd alloy or the surface of the CZL supports. The closer interaction between the support and separate PMOx particles highly dispersed on the surface could stabilize the precious metals and promote the dynamic oxygen storage/release capacity (DOSC) and oxygen mobility, which increases the concentration of surface-active oxygen species, thereby resulting in superior catalytic performance for HC and NOx elimination and the broadening of the dynamic operation window. The formation of the Pt–Pd alloy also obviously improves the thermodynamics of the samples. The Pt0.8Pd0.2/CZL catalyst exhibits the best catalytic activity for NO and HC conversions among all the catalysts, which could be attributed to the larger DOSC values and the enhanced activation of surface oxygen. Moreover, the presence of H2O and CO2 has little influence on the catalytic performance of Pt0.8Pd0.2/CZL.

Recently, single-atom catalysts (SACs) are of great interest in the field of catalysis. Current research shows that it is a potential and feasible development direction for precious metal materials to be made into SACs. Reducing the metal content as much as possible gives the single atom catalyst an obvious cost advantage. However, very low metal loading does not always provide sufficient catalytic activity for SACs. In some catalytic reactions, the deficiency of low catalyst loading can be offset by the increase in catalyst usage. But the excessive use of a catalyst may lead to the loss of mass transport and then the power density. The single atom and high loading might seem like a paradoxical concept but for catalysts, the sufficiently high specific catalytic activity evolves into a most critical parameter for SACs. Synthesizing high loading SACs under control will be an important direction in the next stage of development. In this review, we focus on the progress of precursor selection, material synthesis, content of single-atom, and some possible solutions for high loading SACs. Meanwhile, we also propose a single atom aerogel catalyst with high loading, which provides more possibility for the future development of catalysts.

High-performance electrocatalysts play a vital role in various sustainable energy conversion and storage technologies. Although enormous carbon-based materials have been developed and exhibited efficient electrocatalytic ability comparable to precious metal catalysts, the obtained blurry structure seriously hampered the understanding of the nature of electrocatalysis. Pyrolysis-free polymers are a competitive type of materials owing to their high-density uniform building units, tailorable chemical structure and diverse topology structure, which demonstrate promising catalytic performances for multifarious important reactions. In particular, the absence of a pyrolysis process promises well-preserved active sites, laying a solid foundation for mechanism research. In this review, the recent developments of pyrolysis-free polymers including porous organic polymers, metal organic frameworks, and linear conjugated polymers for oxygen electrocatalysis are summarized. The engineering strategies and their influence on boosting the electrocatalytic performance are concluded, particularly the impact of electronic structure engineering and hybrid synergistic effect. Finally, we further discuss current challenges and future directions for maximizing the advantages of polymer-based electrocatalysts without pyrolysis. This review aims to highlight the importance of pyrolysis-free polymer-based electrocatalysts and their potential to become the guideline for preparing high practical value catalysts by virtue of their clear structure–activity relationship.

Most better performing water splitting electrocatalysts are scarce, and their use increases the cost of production of H2via electrolysis. Among the best performing noble/precious metal electrocatalysts, Ru is most notable because it acts as an excellent electrocatalyst for both oxidation and reduction reactions of water responsible for the H2 production. In fact, Ru outperforms Pt/C as the state-of-the-art water reduction electrocatalyst in alkali. However, the cost-wise more expensive Ru (than Pt and Ir) could not be extensively used in water electrolysis to avoid further increase in the cost of H2 production. Recently, there has been a renewed interest in Ru and is being intensively investigated with various structural and chemical modifications at the nano-level for catalytic water electrolysis with and without other materials. However, there is no comprehensive review that summarizes and analyzes recent developments in water splitting electrocatalysts that are modulated with Ru. Hence, this review is devoted to bringing out the strategies involved in harvesting the best of water splitting electrocatalysts by Ru-tweaking. The same is also benchmarked against their performance at different conditions. Besides, a detailed note on water splitting electrocatalysis and mechanisms involving Ru are given with insights on the phenomena that make it an active interface for water electrolysis.

The performance and cost of electrocatalysts play an important role in the development and application prospects of energy conversion technology. Single-atom catalysts (SACs) have constituted a new frontier in the field of catalytic science in recent years. As a non-precious metal, iron (Fe)-SACs show great potential in the field of electrocatalysis, which is comparable to or even better than the performance of precious metal catalysts. However, a robust, generic synthetic strategy toward atomically dispersed Fe catalysts is still lacking, which is still a formidable challenge to maintain the dispersion of Fe atoms at high temperatures and to obtain high catalytic activity. In this review, the latest progress in the synthesis of Fe-SACs is introduced and summarized, and the electrochemical applications of Fe-SACs are further summarized and discussed. Herein, the relationship between the structural characteristics and performance of Fe-SACs is further introduced and discussed. Finally, the existing problems and development prospects of Fe-SACs are discussed.

Ultra low PtPd alloy deposited on Ni12P5 nanostructures (PtPd/Ni12P5) exhibited enhanced ORR activity (onset: 1.003 V and E1/2:0.95 V) on par with commercial Pt/C and superior OER activity with 81% reduction of the precious metal compared to the commercial catalyst.

Precious metal nanometric catalysts are widely used in the removal of harmful substances. In the process of synthesis and catalytic reaction, it is particularly important to study green and simple synthesis methods and high catalytic efficiency. In this paper, a green one-step method was used to synthesize the Fe(OH)3/Fe2O3@Au composite catalyst, in which Au was single atom-dispersed. The removal of 4-nitrophenol (4-NP), a typical dangerous chemical widely existing in factory waste gas, waste water and automobile exhaust gas, was catalysed by Fe(OH)3/Fe2O3@Au. The catalytic performance of Fe(OH)3/Fe2O3@Au with different synthesis conditions (different amounts of MES, NaBH4, FeSO4, Au and Pt) on the 4-NP reduction reaction were systematically studied. Finally, the stability and recyclability of Fe(OH)3/Fe2O3@Au composite nanocatalyst were investigated thoroughly.

Heterobinuclear catalysts capable of bimetallic cooperative bond activation provide an alternative pathway to approach the discovery of novel and unique reactivity and selectivity in catalytic transformations, complementing more traditional mononuclear precious metal catalysts. This review summarizes recent advances in homogenous catalysis using heterobimetallic carbonyl catalysts with polar metal–metal interactions.1 Introduction2 Hydrogenation and Hydrofunctionalization3 Carbonylation and Carboxylation4 Oxidative Transformations5 Conclusion and Outlook

To meet the sharp increase in demand for clean and renewable energy, it is necessary to develop new energy-conversion and storage technologies, such as proton exchange membrane fuel cells (PEMFCs) and metal-air/oxygen batteries (MABs). Due to the sluggish reaction kinetics of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) in the cathodes of PEMFCs and MABs, significant amounts of precious metal catalysts need to be used, driving up the cost of fuel cells and MABs and thereby hindering their commercialization on a large scale. Transition metal and nitrogen co-doped carbonaceous catalysts (M/N/C) have high catalytic activity towards the ORR and OER once the catalysts are modified with certain promoters/additives. In addition, M/N/C catalysts can be prepared from abundant, inexpensive materials, making their cost negligible compared with precious metal catalysts, a development that would efficiently decrease the cost of PEMFCs and MABs. In last decade, numerous researchers have attempted to realize these applications of M/N/C catalysts, and some exciting results have been achieved, making these promising replacements for precious metal catalysts. However, some serious problems and significant challenges remain. In this paper, we review the research on the application of M/N/C analogue catalysts in PEMFCs and MABs in the last 10 years, indicate the remaining challenges, and suggest the future research directions.

The typically the Haber-Bosch process of nitrogen (N2 ) reduction to ammonia (NH3 ) production, expends a lot of energy, resulting in severe environmental issues. Electro-catalytic N2 reduction to NH3 formation by renewable resources is one of the effective ways to settle the issue. However, the electro-catalytic performances and selectivity of catalysts for electrochemical nitrogen reduction reaction (NRR) are very low. Therefore, it is of great significance to develop more efficient electro-catalysts to satisfy the needs of practical use. Among the reported catalysts, those based on Group VIII noble metals heterogeneous catalysts display excellent NRR activities and high selectivity because of their good conductivity, rich active surface area, unfilled d-orbitals, and the abilities with easy adsorption of reactants and stable reaction intermediates. Herein, we will introduce the progress of Group VIII precious metals heterogeneous catalysts applied in the electrocatalytic N2 reduction reaction. Then single precious metal electrocatalysts, precious metal alloy electrocatalysts, heterojunction structure electrocatalysts, and precious metal compounds based on the strategies of morphology engineering, crystal facet engineering, defect engineering, heteroatom doping, and synergetic interface engineering will be discussed. Finally, the challenges and prospects of the NH3 synthesis have been put forward. In the review, we will provide helpful direction to the development of effective electro-catalysts for catalytic N2 reduction reaction.

Ammonia (NH3) is mainly produced through the traditional Haber–Bosch process under harsh conditions with huge energy consumption and massive carbon dioxide (CO2) emission. The nitrogen electroreduction reaction (NERR), as an energy-efficient and environment-friendly process of converting nitrogen (N2) to NH3 under ambient conditions, has been regarded as a promising alternative to the Haber–Bosch process and has received enormous interest in recent years. Although some exciting progress has been made, considerable scientific and technical challenges still exist in improving the NH3 yield rate and Faradic efficiency, understanding the mechanism of the reaction and promoting the wide commercialization of NERR. Single-atom catalysts (SACs) have emerged as promising catalysts because of their atomically dispersed activity sites and maximized atom efficiency, unsaturated coordination environment, and unique electronic structure, which could significantly improve the rate of reaction and yield rate of NH3. In this review, we briefly introduce the unique structural and electronic features of SACs, which contributes to comprehensively understand the reaction mechanism owing to their structural simplicity and diversity, and in turn, expedite the rational design of fantastic catalysts at the atomic scale. Then, we summarize the most recent experimental and computational efforts on developing novel SACs with excellent NERR performance, including precious metal-, nonprecious metal- and nonmetal-based SACs. Finally, we present challenges and perspectives of SACs on NERR, as well as some potential means for advanced NERR catalyst.

A new facile method for preparing highly dispersed precious metal catalysts was proposed in this work. Highly dispersed Pt supported on LaNiO3/SiO2 were prepared by using LaNi1-xPtxO3 perovskite as precursors. The catalytic performances of CO oxidation over the prepared catalytsts were investigated. The structural features of the catalysts were characterized by N2 adsorption-desorption, XRD, H2-TPR, TEM, EXAFS, CO-TPD and O2-TPD techniques. The result indicated that nanocrystalline of LaNi1-xPtxO3 was supported on SiO2. Reducing LaNi1-xPtxO3/SiO2 could make Pt from the interior of the perovskite crystal lattice onto the surface and then form highly dispersed Pt on the support of LaNiO3/SiO2. As the platinum content was 0.5% or less, platinum atoms could distribute highly even maybe in single atoms. The catalytic test revealed that LaNi0.95Pt0.05O3/SiO2 exhibited a significant activity and stability for CO oxidation, as well as excellent performance in the presence of both 15 vol.% H2O and 12.5 vol.% CO2. It has been demonstrated that the highly dispersed Pt, the easy reducibility, and sufficient surface oxygen species were responsible for the high catalytic activity of LaNi0.95Pt0.05O3/SiO2 catalyst.

The replacement of precious metal catalysts with pyridinic and graphitic-N sites that are earth-abundant and of low-cost and enriched with a high concentration for oxygen reduction reaction (ORR) i...

The use of precious metals in many areas, such as printed circuit boards, catalysts, and targeted drugs, is increasing due to their unique physical and chemical properties, but their recovery remains a great challenge. Here, we report a sandwiched Ti3C2Tx MXene/carbon nanotube (CNT) hybrid membrane, where the CNT isolates and supports the MXene sheets, which act as a reducing agent. The hybrid membrane shows excellent ability to capture precious metal ions in solution with a high flux. The water permeability of the membrane reaches 437.6 L m-2 h-1 bar-1 (2.46 × 10-18 m2), about 202 times higher than that of a pure Ti3C2Tx membrane, and captures 99.8% Au(III) from a solution with an extremely low concentration of 20 ppm. The desirable precious metal trapping capability of the Ti3C2Tx-CNT film is due to the high redox activity of C-Ti-OH. This work provides an efficient way for the recovery of precious metal ions from wastewater.

Hydrosilylation of multiple carbon–carbon bonds is a well-known process for the construction of organosilicon compounds. Nowadays, precious metal catalysts, especially platinum complexes, still occupy dominant positions in such processes. However, one important member of the precious metal family, iridium, is less used in this field. As early research mainly focused on developing stable and effective iridium catalysts, recent advances have disclosed the specific efficiency of simple iridium catalytic systems in the synthesis of functional organo­silicon compounds. This short review summarizes the utilization of iridium complexes for the hydrosilylation of alkenes and alkynes, with an emphasis on the recent advances published in the last decade.1 Introduction2 Iridium-Catalyzed Hydrosilylation of Alkenes3 Iridium-Catalyzed Hydrosilylation of Alkynes4 Conclusions and Perspectives

Significant reduction of the precious metal catalyst loading is one of the key challenges for the commercialization of proton-exchange membrane water electrolyzers. In this work we combine IrOx nanofibers with a conventional nanoparticle-based IrOx anode catalyst layer. With this hybrid design we can reduce the iridium loading by more than 80% while maintaining performance. In spite of an ultralow overall catalyst loading of 0.2 mg(Ir)/cm(2), a cell with a hybrid layer shows similar performance compared to a state-of-the-art cell with a catalyst loading of 1.2 mg(Ir)/cm(2) and clearly outperforms identically loaded reference cells with pure IrOx nanoparticle and pure nanofiber anodes. The improved performance is attributed to a combination of good electric contact and high porosity of the IrOx nanofibers with high surface area of the IrOx nanoparticles. Besides the improved performance, the hybrid layer also shows better stability in a potential cycling and a 150 h constant current test compared to an identically loaded nanoparticle reference.

Urban mining of precious metals from electronic waste, such as printed circuit boards (PCB), is not yet feasible because of the lengthy isolation process, health risks, and environmental impact. Although porous polymers are particularly effective toward the capture of metal contaminants, those with porphyrin linkers have not yet been considered for precious metal recovery, despite their potential. Here, we report a porous porphyrin polymer that captures precious metals quantitatively from PCB leachate even in the presence of 63 elements from the Periodic Table. The nanoporous polymer is synthesized in two steps from widely available monomers without the need for costly catalysts and can be scaled up without loss of activity. Through a reductive capture mechanism, gold is recovered with 10 times the theoretical limit, reaching a record 1.62 g/g. With 99% uptake taking place in the first 30 min, the metal adsorbed to the porous polymer can be desorbed rapidly and reused for repetitive batches. Density functional theory (DFT) calculations indicate that energetically favorable multinuclear-Au binding enhances adsorption as clusters, leading to rapid capture, while Pt capture remains predominantly at single porphyrin sites.

This review article summarizes the key published research on the topic of bio-oil upgrading using catalytic and non-catalytic supercritical fluid (SCF) conditions. The precious metal catalysts Pd, Ru and Pt on various supports are frequently chosen for catalytic bio-oil upgrading in SCFs. This is reportedly due to their favourable catalytic activity during the process including hydrotreating, hydrocracking, and esterification, which leads to improvements in liquid yield, heating value, and pH of the upgraded bio-oil. Due to the costs associated with precious metal catalysts, some researchers have opted for non-precious metal catalysts such as acidic HZSM-5 which can promote esterification in supercritical ethanol. On the other hand, SCFs have been effectively used to upgrade crude bio-oil without a catalyst. Supercritical methanol, ethanol, and water are most commonly used and demonstrate catalyst like activities such as facilitating esterification reactions and reducing solid yield by alcoholysis and hydrolysis, respectively.

Recently, nitrogen-doped porous carbon supported single atom catalysts (SACs) have become one of the most promising alternatives to precious metal catalysts in oxygen reduction reaction (ORR) due to their outstanding performance, especially those derived from porphyrin-based materials. However, most of them involve other metal residuals, which would cause the tedious pre- and/or post-treatment, even mislead the mechanistic investigations and active-site identification. Herein, we report a precursor-dilution strategy to synthesize Fe SACs through the Schiff-based reaction via co-polycondensation of amino-metalloporphyrin, followed by pyrolysis at high temperature. Systematic characterization results provide the compelling evidence of the dominant presence of atomically dispersed Fe-N x species. Our catalyst shows superior ORR performance with positive half-wave potential ( E 1/2= 0.85 V vs. RHE) in alkaline condition and moderate activity ( E 1/2= 0.68 V vs. RHE) under the acidic condition, excellent methanol tolerance and good long-term stability. All the results indicate Fe SACs would be a promising candidate for replacing the precious Pt in metal-air batteries and fuel cells.

The replacement of precious metal electrocatalysts by highly active and cost-efficient alternatives for complete water splitting at low voltage has recently attracted a growing attention. In this work, it is reported how semigraphitized carbons are transformed into highly active electrocatalysts for hydrogen evolution reaction. Moreover, heat treatment at 400 °C under certain conditions can be a simple and cheaper approach to perform surface modification of low-graphitized carbons. This leads to a remarkable modulation on their catalytic activity. These materials can offer promising low-cost catalysts for water decomposition.

A passive catalytic reactor without heating is required to enhance the safety of a fusion facility. A precious metal catalyst without heating is not suitable to oxidize tritium under conditions of ...

Palladium is a precious metal, which has been widely used for various organic transformations in the past decades. Currently, the palladium-catalyzed direct activation of the aromatic ring C–H bonds is one of the frontier areas in organic chemistry, and the progress of research in this field is very rapid. Compared with other transition metals, palladium has the advantages of high catalytic activity and strong selectivity. Combining the domestic and foreign scholars' research on this aspect, this paper summarizes the research progress of the palladium-catalyzed activation of aromatic ring C–H bonds in the past ten years. Keywords: Aromatic ring C–H bonds, Palladium catalyst, Direct conversion

The incorporation of donor-type substituents on the allene core opens up the possibility of coordination complexes in which the metal is bonded to the donor groups, with or without interaction with the double bond system. Despite the challenges in the synthesis of such allene-containing metal complexes, their unique 3D environments and dual functionality (allene and metal) could facilitate catalysis and interaction with chemical and biological systems. Bis(pyridyl)allenes are presented here as robust ligands for novel Pd(II), Pt(IV) and Au(III) complexes. Their synthesis, characterisation and first application as catalysts of benchmark reactions for Pd, Pt and Au are presented with interesting reactivity and selectivities. The complexes have also been probed as antimicrobial and anticancer agents with promising activities, and the first studies on their unusual interaction with several DNA structures will open new avenues for research in the area of metallodrugs with new mechanisms of action.

Colloidal syntheses of nanoparticles (NPs) are one of the preferred approaches to prepare precious metal catalysts. Unfortunately, most colloidal syntheses developed require stabilizing agents to avoid NP agglomeration and/or control NP size and morphology. While these surfactants can bring positive features, they typically block catalytically active sites on the NP surface. As a consequence, these additives often need to be removed by energy and/or time consuming steps, at the risk of complicating the synthesis, introducing irreproducibility and negatively altering the structure and properties of the prepared catalysts. Fortunately, several surfactant-free colloidal syntheses have been reported and are being developed. This Mini Review addresses the challenges in defining a surfactant-free colloidal synthesis of NPs and survey established and emerging strategies to obtain surfactant-free colloidal precious metal NPs. A focus is given to approaches that show promising features to bridge the gap between fundamental and applied research towards industrial applications.

Metal-gas batteries draw a lot of attention due to their superiorities in high energy density and stable performance. However, the sluggish electrochemical reactions and associated side reactions in metal-gas batteries require suitable catalysts, which possess high catalytic activity and selectivity. Although precious metal catalysts show a higher catalytic activity, high cost of the precious metal catalysts hinders their commercial applications. In contrast, nonprecious metal catalysts complement the weakness of cost, and the gap in activity can be made up by increasing the amount of the nonprecious metal active centers. Herein, recent work on carbon-based nonprecious metal catalysts for metal-gas batteries is summarized. This review starts with introducing the advantages of carbon-based nonprecious metal catalysts, followed by a discussion of the synthetic strategy of carbon-based nonprecious metal catalysts and classification of active sites, and finally a summary of present metal-gas batteries with the carbon-based nonprecious metal catalysts is presented. The challenges and opportunities for carbon-based nonprecious metal catalysts in metal-gas batteries are also explored.

There appears to be consensus among the general public that curtailing harmful emissions resulting from industrial, petrochemical and transportation sectors is a common good. However, there is also a need for balancing operating expenditures for applying the required technical solutions and implementing advanced emission mitigation technologies to meet desired sustainability goals. The emission of NOx from Fluid Catalytic Cracking (FCC) units in refineries for petroleum processing is a major concern, especially for those units located in densely populated urban settings. In this work we strive to review options towards cost-efficient and pragmatic emissions mitigation using optimal amounts of precious metal while evaluating the potential benefits of typical promoter dopant packages. We demonstrate that at present catalyst development level the refinery is no longer forced to make a promoter selection based on preconceived notions regarding precious metal activity but can rather make decisions based on the best “total cost” financial impact to the operation without measurable loss of the CO/NOx emission selectivity.

The direct use in catalysis of precious metal recovery products from industrial and consumer waste is a very promising recent area of investigation. It represents a more sustainable, environmentally benign, and profitable way of managing the low abundance of precious metals, as well as encouraging new ways of exploiting their catalytic properties. This review demonstrates the feasibility and sustainability of this innovative approach, inspired by circular economy models, and aims to stimulate further research and industrial processes based on the valorisation of secondary resources of these raw materials. The overview of the use of recovered gold and palladium in catalytic processes will be complemented by critical appraisal of the recovery and reuse approaches that have been proposed.