High Cost Of Noble Metals Research Articles

Exploring Pt-Cu Synergistic Effects on Porous SiO2 Support With Different Pt Loadings for Low-temperature Oxidation of CO and C3H6

To address the high cost of noble metals, this study aims to optimize Pt loading and the synergistic effect of Cu on porous SiO2 support for low-temperature oxidation of CO and C3H6. A simulated test bench system was used to evaluate the performance of PtxCu1/SiO2 (where x= 0, 0.3, 0.5, 0.7, and 1wt%), Cu1/SiO2 and Ptx/SiO2 (where x= 0.5 and 1wt%) catalysts with varying Pt loadings. Comprehensive characterization, including BET, XRD, SEM, TEM, and XPS was conducted to assess particle size, structure, and surface morphology. The effects of Pt incorporation on reduction and oxidation properties were further examined using H2-TPR and CO-TPD techniques. Results demonstrated a significant enhancement in catalytic activity with the addition of Cu confirming a synergistic interaction between Pt and Cu. This synergy was particularly pronounced in lower Pt loadings, where PtxCu1/SiO2 composites outperformed Ptx/SiO2 in catalytic activity. Pt addition reduced the particle size, which resulted in the creation of PtCu alloy, with 1 and 0.7% wt Pt loading exhibiting comparable effects in CO conversion and 0.7% Pt loading exhibiting better activity at higher temperatures in C3H6 oxidation indicating that catalytic activity was maintained even with a reduced Pt loading. Additionally, minimal difference in activity for C3H6 oxidation was observed among PtxCu1/SiO2 catalysts with 0.7, 0.5, and 0.3wt% Pt loadings as indicated by T50 and T80 values. Reducing Pt loading from 0.7wt% had minimal impact on catalytic efficiency for C3H6 oxidation with catalysts maintaining high activity. 0.7wt% Pt loadings provide sufficient active sites for effective CO and HC oxidation. The enhanced catalytic activity and stability of bimetallic catalysts over monometallic Cu/SiO2 and Pt/SiO2 result from the simultaneous presence of active sites created by the synergetic effect of PtCu alloy formation with optimal ratio and well-optimized surface. These findings demonstrate the potential to optimize Pt usage without compromising catalytic performance, offering a cost-effective approach to catalyst design.

Sustainable Production of Chemicals via Hydrotreating of CO2 and Biomass Derived Molecules Using Heterogeneous Noble Metal Oxide Catalysts

AbstractThe noble metals are widely used in heterogeneous catalysis and automobile industry. The limited natural sources and high cost of noble metals dictates improving the efficiency of modern industry. This review considers the applications of noble metal oxide as potential solutions to the sustainability issues, including biomass conversion, CO2 capture and conversion, green fuel production, etc. Noble metal oxides with their different compositions (monometallic and bimetallic) and structures exhibit a wide range of properties in heterogeneous catalysis. Although platinum metals in an oxidized form may not be the most common choice in hydroprocesses; recently, there have been studies indicating that they were highly active and selective catalysts in hydrogenation and hydrogenolysis. This review outlines the most established noble metal oxide catalysts used in hydrogenation catalysis and shed the light on the relation of noble metal oxide species to catalyst selectivity based on state‐of‐the‐art techniques. Finally, the perspectives on the application of noble metal oxide catalysts to produce value‐added chemicals are discussed.

Novel IP2C sensors with flexible electrodes based on plasma-treated conductive elastomeric nanocomposites

Ionic polymer-metal composites (IPMC) are devices composed of metallic electrodes and an ionomeric polymer membrane in a ‘sandwich’ architecture and. Their main property is electromechanical actuation or sensing based on the movement of ions. Metallic electrodes are commonly used for their high electrical conductivity, malleability, and chemical resistance. However, the high cost of noble metals, such as platinum, long manufacturing time, and fatigue failure limit their application. Therefore, the replacement of metallic electrodes with conductive elastomeric nanocomposites (CENs) was evaluated to reduce the costs and complexity of manufacturing the device and increase its working life. In this work, carbon nanotubes were used as the conductive fillers. The dispersion to achieve high electrical conductivity was carried out directly in the synthetic or natural polyisoprene rubber latex assisted by surfactant and high-power sonication. To improve the adhesion between the elastomeric electrode and the ionic membrane (Nafion), plasma treatment with atmospheric air was applied as a surface modifier. This treatment improved the hydrophilicity and adhesion of the rubbers by forming oxygenated groups and increasing the surface nanoroughness. In this way, ionomeric polymer–polymer composite (IP2C) devices were fabricated using Nafion and plasma-modified CENs, this type of electrode is unprecedented in the literature for this application. These devices showed displacement and strain sensing capacity at levels close to the conventional IPMC in all tested frequency ranges and applied accelerations. Notably, the IP2C obtained better resolution at low frequencies than the control.

Full-spectrum plasmonic semiconductors for photocatalysis.

Localized surface plasmon resonance (LSPR) of noble metal nanoparticles can focus surrounding light onto the particle surface to boost photochemical reactions and solar energy utilization. However, the rarity and high cost of noble metals limit their applications in plasmonic photocatalysis, forcing researchers to seek low-cost alternatives. Recently, some heavily doped semiconductors with high free carrier density have garnered attention due to their metal-like LSPR properties. However, plasmonic semiconductors have complex surface structures characterized by the presence of a depletion layer, which poses challenges for active site exposure and hot carrier transfer, resulting in low photocatalytic activity. In this review, we introduce the essential characteristics and types, synthesis methods, and characterization techniques of full-spectrum plasmonic semiconductors, elucidate the mechanism of full-spectrum nonmetallic plasmonic photocatalysis, including the local electromagnetic field, hot carrier generation and transfer, the photothermal effect, and the solutions for the surface depletion layer, and summarize the applications of plasmonic semiconductors in photocatalytic environmental remediation, CO2 reduction, H2 generation, and organic transformations. Finally, we provide a perspective on full-spectrum plasmonic photocatalysis, aiming to guide the design and development of plasmonic photocatalysts.

Interfacial synergy between Pt3Co nanoparticles and CoO for efficient ammonia borane hydrolysis

Ammonia borane (AB, NH3BH3) with the high H2 content has been regarded as a promising material for chemical hydrogen storage. AB can hydrolyze to release H2 under the catalysis of noble-metal catalysts with high activity, but the high cost of noble-metals and their poor long-term stability prohibit the large-scale applications. Developing more cost-effective and stable catalysts by introducing cheap transition metal elements has been a promising strategy. Herein, we adopted a step-by-step precipitation method to synthesize bimetallic Pt-Co catalysts supported on rutile TiO2, which show significantly improved performance in AB hydrolysis reaction. The optimized 0.9Pt3.5Co/TiO2 catalyst (with the Pt and Co loadings of 0.9 and 3.5 wt%, respectively) exhibits an extremely high H2 generation rate, showing a turnover frequency value of 2163 molH2 molPt-1 min−1 at 298 K, 9 times higher than that of 0.9Pt/TiO2 catalyst and superior to those of most of the reported Pt-based catalysts. Structure characterizations and theoretical calculations reveal that the promoted AB hydrolysis performance arises from the interfacial synergistic effect between the supported Pt3Co alloy and cobalt oxide CoO, which accelerates the B-H bond cleavage and water activation, respectively. The excellent AB hydrolysis performance of the Pt-Co catalysts indicates the great prospects of alloy-oxide interfaces in the field of liquid phase chemical hydrogen storage.

Alloyed Pt Single‐Atom Catalysts for Durable PEM Water Electrolyzer

AbstractThe high cost of noble metals is one of the key factors hindering the large‐scale application of proton exchange membrane (PEM) water electrolyzer for hydrogen production. Recently, single‐atom catalysts (SACs) with a potential of maximum atom utilization efficiency enable lowering the metal amount as much as possible; unfortunately, their durability remains a challenge under PEM water electrolyzer working conditions. Herein, a highly‐stable alloyed Pt SAC is demonstrated through a plasma‐assisted alloying strategy and applies to a PEM water electrolyzer. In this catalyst, single Pt atoms are firmly anchored onto a Ru support via a robust metal–metal bonding strength, as evidenced by these complementary characterizations. This SAC is used in a PEM water electrolyzer system to achieve a cell voltage as low as 1.8 V at 1000 mA cm−2. Impressively, it can operate over 1000 h without obvious decay, and the catalyst is present in the form of individual Pt atoms. To the knowledge, this will be the first SAC attempt at a cell level toward long‐term PEM. This work paves the way for designing durable SACs employed in the actual working condition in the PEM water electrolyzer.

A self-cleaning SERS substrate based on flower-like Au@MoS2/Ag NPs with photocatalytic ability

Noble metals such as gold and silver play important role in the fabrication of SERS substrates, however, the high cost of noble metals has become an obstacle when SERS start to move out of the research laboratory and into practice. Recently, self-cleaning substrates have drawn more and more attention due to their recyclable ability and further reducing cost. In this work, a flower-like Au@MoS2/Ag NPs nanocomposite with core-shell structure was synthesized by hydrothermal method. The employment of MoS2 endows the substrate with a high adsorption capacity and photocatalytic ability. Finally, a highly sensitive, self-cleaning, and recyclable SERS substrate was constructed by combining the synergistic effect of noble metal nanoparticles (Au, Ag) and the photocatalytic ability of MoS2. Methylene blue (MB) was used to evaluate the SERS performances of the as-prepared substrate, and the results show that the as-prepared substrate has good signal uniformity with relative standard deviation (RSD) of 8.2 %, and good batch-to-batch stability with the RSDs of 4.9 %, 5.7 %, and 5.3 % at 1625 cm−1, 1401 cm−1, and 451 cm−1, respectively. In the range of 10−5–10−10 M, the concentration of the analyte showed a good linear relationship with the Raman peak intensity at 1625 cm−1, with the correlation coefficient R2 of 0.9821, and the detection limit was 8.9 × 10−11 M. In addition, the photocatalytic performance of the substrate was investigated, 97.1 % of the MB was degraded under the irradiation of the Xe lamp for 100 min, and the SERS signal remained at 62.8 % of the initial signal after 8 cycles. The flower-like Au@MoS2/Ag NPs self-cleaning SERS substrate developed in this work shows good renewable performance and is expected to be used as a new SERS substrate in food, medicine, environmental, and other analytical fields.

N, S co-doped carbon film wrapped Co nanoparticles for boosting oxygen reduction reaction

Electrochemical energy (e.g., fuel cell and metal-air batteries) is featured by large theoretical energy density, high conversion efficiency, safe operation and pollution-free emission. However, the sluggish dynamics of oxygen reduction reaction (ORR) and high cost of noble metals hinder their widespread commercial applications in electrochemical energy devices. Herein, we present a method for the preparation of the N, S co-doped carbon film wrapped Co nanoparticles (Co/NSC) for ORR by aging and then pyrolyzing the mixture of cobalt salt and 1-(p-Toluenesulfonyl)imidazole. The co-doping of N and S facilitates the electron rearrangement of the carbon film, resulting in a rapid electron transfer. The core-shell structure enhances the interaction between N, S co-doped carbon film and Co nanoparticles. These features endow the Co/NSC catalyst an excellent ORR with a half-wave potential of 0.860 V and limiting current density of 6.2 mA cm-2, besides the superior anti-methanol. The Co/NSC catalyst as the air cathode grants the assembled zinc-air battery high open circuit voltage (1.467 V), large peak power density (156.2 mW cm-2), great specific capacity (747.9 mAh gZn-1), and excellent stability. Thus, the prepared Co/NSC catalyst exhibits a promising application in zinc-air battery. This work provides an approach for the synthesis of the carbon-shell coated non-noble metal catalyst and its subsequent applications in oxygen electrocatalysis.

Ti-Doped SnO2 Supports IrO2 Electrocatalysts for the Oxygen Evolution Reaction (OER) in PEM Water Electrolysis

The development of polymer electrolyte membrane electrolysis of water is mainly limited by the high cost of noble metals and inadequate stability owing to the slow reaction kinetics of the oxygen evolution reaction and the restrictions of strongly acidic operating environments. To improve the utilization of noble metals, we use Ti-doped SnO2 as a carrier to support active species IrO2. The results show that the introduction of Ti element can inhibit the grain growth and help to improve the electrical conductivity of SnO2. Electrochemical tests for the catalysts show that 40 wt % IrO2/TSO has the best mass-normalized charge (231.24 C g–1 IrO2) and current density (714.85 A g–1 IrO2) at 1.6 V with the overpotential of only 271 mV at 10 mA cm–2, which is attributed to the outstanding dispersion effect of Ti-doped SnO2 and the synergy between the active species and the introduction of Ti element. The comprehensive advantages exhibited by the Ti-doped SnO2 support provide an alternative solution to reduce the cost of noble metal catalysts by improving the catalytic activity and stability.

Hydrogenation Reactions with Synergistic Catalysis of Pd single atoms and nanoparticles under Near-Ambient Conditions.

Due to the limited resources and high cost of noble metals, boosting their catalytic activities is highly desired in the current catalysis industry. Here, we report a synergetic catalyst, combining Pd2+ and Pd0 species in a nitrogen-doped porous carbons (NPC), which shows boosted catalytic activities in hydrogenation reactions of organic nitro compounds (nitrobenzene, 4-nitrophenol, 1-nitronaphthalene and 1-nitropropane) under near ambient conditions. This synergetic catalyst NPC-[Pd] was synthesized by partial reduction of a palladium-loaded NPC. The catalytic activities and selectivity of NPC-[Pd] for hydrogenation were enhanced significantly compared with those of NPC-Pd2+ or NPC-Pd0 nanoparticles. Theoretical calculations show that H2 preferentially dissociates on Pd nanoparticles, and then organic molecules (nitrobenzene) can be captured and react with the dissociated H atom on Pd2+ sites. Similar reaction procedure also occur on Pt or Rh. Hydrogenation of different aromatic compounds with different functional groups (naphthalene, 4-nitrochlorobenzene, benzaldehyde and acetophenone) confirmed the broad excellent catalytic activity of this synergistic catalyst.

Computation and Machine Learning for Catalyst Discovery

Towards a sustainable energy future, it is essential to develop new catalysts with improved properties for key catalytic systems such as Haber-Bosch process, water electrolysis and fuel cell. Unfortunately, the current state-of-the-art catalysts still suffer from high cost of noble metals, insufficient catalytic activity and long-term stability. Furthermore, the current strategy to develop new catalysts relies on “trial-and-error” method, which could be time-consuming and inefficient. To tackle this challenge, atomic-level simulations have demonstrated the potential to facilitate catalyst discovery. For the past decades, the simulations have become reasonably accurate so that they can provide useful insights toward the origin of experimentally observed improvements in catalytic properties. In addition, with the exponential increase in computing power, high-throughput catalyst screening has become feasible. More excitingly, recent advances in machine learning have opened the possibility to further accelerate catalyst discovery. Herein, we introduce recent applications and challenges of computation and machine learning for catalyst discovery.

Nickel nanocrystal/sulfur-doped carbon composites as efficient and stable electrocatalysts for urea oxidation reaction

Urea oxidation reaction (UOR) is an anodic reaction in the electrochemical generation hydrogen and also a crucial half-reaction of direct urea fuel cell (DUFC). However, the scarcity and high cost of noble metals severely limited their application as electrocatalysts for UOR. Herein, we have prepared the composite (Ni@S-C) of nickel nanocrystal embedded in sulfur-doped carbon through facile impregnation method followed by calcination method. X-ray photoelectron spectroscopy (XPS) study indicates the Ni(III) species in Ni@S-C are more positive than typical Ni(III), which serve as the active sites for UOR. Meanwhile, the active Ni(III) is coordinated with S, which facilitates charge transfer and chemisorption of active oxygen species. Under optimal experimental conditions, the Ni@S-C-500 catalyst indicates an excellent UOR activity of 177 mA cm−2 in 1 M KOH + 0.33 M urea at 1.656 V, which was 3.75 times as much as that of the commercial Pt/C catalyst. Meanwhile, the optimal Ni@S-C-500 catalyst also presents a current density (j) retention rate of 80% after 12 h UOR test, which is much higher than that of the commercial Pt/C catalyst (<15% retention). This work provides a strategy for preparing stable and active Ni-based electrocatalyst for the UOR.

Lanthanum strontium cobaltite as interconnect in oxide thermoelectric generators

Issues related to use of metallic interconnects in oxide thermoelectric generators (TEGs) need to be addressed to secure performance and durability. Metal interconnects suffer from high cost of noble metals or chemical instability and contact resistance of non-noble metals, arising from oxidation, evaporation, and delamination in the oxidising conditions of ambient air at high operating temperatures. This work introduces the use of a stable and highly conducting ceramic oxide, in our case p-type lanthanum strontium cobaltite (La0.6Sr0.4CoO3, LSC) as interconnect. We verified the thermochemical stability of LSC in contact with p-type Ni0.98Li0.02O (Li–NiO) and n-type Zn0.98Al0.02O (Al–ZnO) and examined the electrical characteristics. An area specific contact resistance (ASRc) of ∼1800 Ω cm2 for a direct p-n junction was reduced to ∼400 mΩ cm2 for a p-LSC-n junction at a temperature of 300 °C, validating the concept. The use of a screen-printed LSC/Al–ZnO composite as a thin interconnect layer was found to decrease the contact resistance of the junction further to ∼260 mΩ cm2 at 300 °C, attributed to increased effective area of the LSC/Al–ZnO p-n junction.

Phase-Controlled NiO Nanoparticles on Reduced Graphene Oxide as Electrocatalysts for Overall Water Splitting.

Efficient water electrolysis is one of the key issues in realizing a clean and renewable energy society based on hydrogen fuel. However, several obstacles remain to be solved for electrochemical water splitting catalysts, which are the high cost of noble metals and the high overpotential of alternative catalysts. Herein, we suggest Ni-based alternative catalysts that have comparable performances with precious metal-based catalysts and could be applied to both cathode and anode by precise phase control of the pristine catalyst. A facile microwave-assisted procedure was used for NiO nanoparticles anchored on reduced graphene oxide (NiO NPs/rGO) with uniform size distribution in ~1.8 nm. Subsequently, the Ni-NiO dual phase of the NPs (A-NiO NPs/rGO) could be obtained via tailored partial reduction of the NiO NPs/rGO. Moreover, we demonstrate from systematic HADDF-EDS and XPS analyses that metallic Ni could be formed in a local area of the NiO NP after the reductive annealing procedure. Indeed, the synergistic catalytic performance of the Ni-NiO phase of the A-NiO NPs/rGO promoted hydrogen evolution reaction activity with an overpotential as 201 mV at 10 mA cm−2, whereas the NiO NPs/rGO showed 353 mV. Meanwhile, the NiO NPs/rGO exhibited the most excellent oxygen evolution reaction performance among all of the Ni-based catalysts, with an overpotential of 369 mV at 10 mA cm−2, indicating that they could be selectively utilized in the overall water splitting. Furthermore, both catalysts retained their activities over 12 h with constant voltage and 1000 cycles under cyclic redox reaction, proving their high durability. Finally, the full cell capability for the overall water electrolysis system was confirmed by observing the generation of hydrogen and oxygen on the surface of the cathode and anode.

Highly Dispersive Metal Atoms Anchored on Carbon Matrix Obtained by Direct Rapid Pyrolysis of Metal Complexes

Highly Dispersive Metal Atoms Anchored on Carbon Matrix Obtained by Direct Rapid Pyrolysis of Metal Complexes

Atomic level engineering of noble metal nanocrystals for energy conversion catalysis

It is commonly known that the performance of electrocatalysts is largely influenced by the size, morphology, composition, and crystalline phase of noble metal nanocrystals. However, the limited reserves and high cost of noble metals largely restrict their industrial applications. Along with the development of characterization techniques, theoretical calculations, and advanced material synthesis methods, modulating the electrocatalytic properties of noble metal nanocrystals at the atomic scale (e.g., monolayer/sub-monolayer, single-atom alloy, ultrafine structure) has been flooding out. Engineering noble metal nanocrystals at the atomic level could not only immensely improve the noble metal atom utilization efficiency and lower the cost, but also boost the catalytic performance. In this review, we summarize the recent advanced progresses of regulating the noble metal nanocrystals at the atomic scale towards energy conversion application. Then, the challenges and perspectives of designing noble metal nanocrystals at the atomic scale in the future are discussed and considered. It is expected that this review will inspire scientists to further study precious metal-based materials for energy-oriented catalysis.

Low-Cost Electrocatalytic Layers for Hydrogen Evolution Reaction Based on Nickel and Cobalt Phosphides: Fabrication Via Codeposition-Annealing Route and XPS Characterization

In an attempt to mitigate the effects of climate changes, modern societies are facing a revolution in energy supply. Future economy will be increasingly dominated by carbon-free and renewable energy sources. In this context, hydrogen will play a fundamental role in the energy transition from fossil to green sources. It offers the possibility to smooth the intermittency typical of many renewable energy sources and it constitutes an ideal complement for batteries in the transport sector. Hydrogen can be easily produced employing water electrolysis, stored in large amounts and subsequently re-electrified in fuel cells. Efficient water electrolysis, however, makes use of noble metal electrocatalysts to lower the overpotential required for the Hydrogen Evolution Reaction (HER) to take place. Due to the limited availability and consequent high cost of noble metals, research is currently focusing on the development of low-cost alternative catalytic materials. One of the most studied electrocatalytic compounds are transition metal phosphides [1]. These materials present remarkable advantages over commonly used Pt based catalysts: comparable performances, lower cost, high abundancy and ease of manufacturing.In the present work, transition metal phosphides were fabricated through a simple and costless codeposition-annealing process. Amorphous Ni-P and Co-P alloys were codeposited with red phosphorus particles and subsequently annealed [2]. The annealing step was applied to promote the formation of intermetallics through interdiffusion between pure phosphorus particles and the metallic matrix. As a result, different phase pure metal phosphides were obtained. The most important advantage of this methodology is the possibility to overcome the compositional limit typical of electrodeposited phosphorus-based alloys. Elemental phosphorus codeposition allows to reach P concentrations higher than 50 % at., whereas simple Ni-P solid solution electrodeposition is compositionally limited to 25 % at. Enhancing P content is fundamental to obtain phosphorus rich compounds like Ni2P and Co2P, which are characterized by high catalytic activities for HER [3]. Furthermore, the technique allows to confine elemental P inside the coating during the annealing step. This peculiarity strongly optimizes material usage and it limits the presence of gaseous phosphorus, which is typical of many phosphorization processes used in literature to obtain metal phosphides [4] and it can result into the formation of the unstable white P allotrope.Obtained nickel and cobalt phosphides were characterized with different techniques (SEM, XRD, EDS) to assess their morphology, phase structure and chemical composition. A special emphasis was placed on XPS characterization. Thanks to its ability to analyze the first superficial layers of the coatings, XPS was employed to determine the chemical state of the elements present on the surface of the electrocatalysts. Being electrocatalysis an interfacial phenomenon, this allowed to link material surface properties with observed electrocatalytic performances.The electrocatalytic HER activity and stability of the different transition metal phosphides were tested in 0.5 M H2SO4. In all cases, remarkable results were obtained, with the lowest overpotential obtained in the case of Co-P/P codeposition and subsequent annealing at 290 °C: 62 mV vs. RHE at a current density of 10 mA/cm2 in 0.5 M H2SO4 solution. This result is in line with the literature available on cobalt phosphides as electrocatalysts [5].[1] P. Xiao et al., Adv. Energy Mater. 5, 1500985 (2015)[2] R. Bernasconi et al., ACS Appl. Energy Mater. 3(7), 6525–6535 (2020)[3] A. R. J. Kucernak et al., J. Mater. Chem. A 2, 17435 (2014)[4] X. Wang et al., Angew. Chem. 54(28), 8188 (2015)[5] Saadi et al., J. Phys. Chem. C 118(50), 29294–29300 (2014)

Nickel and Cobalt Phosphides Fabricated through a Codeposition-Annealing Technique As Low-Cost Electrocatalytic Layers for Efficient Hydrogen Evolution Reaction

In the perspective of sustainable development, future economy will be increasingly dominated by carbon-free and renewable energy sources. In this context, hydrogen will play a fundamental role in the energy transition from fossil to green sources. Hydrogen can be easily produced employing water electrolysis, stored in large amounts and subsequently re-electrified in fuel cells. It offers the possibility to smooth the intermittency typical of many renewable energy sources and it constitutes an ideal complement for batteries in the transport sector. Efficient water electrolysis, however, makes use of noble metal electrocatalysts to lower the overpotential required for the Hydrogen Evolution Reaction (HER) to take place. Due to the limited availability and consequent high cost of noble metals, research is currently focusing on the development of low-cost alternative catalytic materials. One of the most studied electrocatalytic compounds are transition metal phosphides [1]. These materials present remarkable advantages over commonly used Pt based catalysts: lower cost, high abundancy and ease of manufacturing. In many cases, phosphides offer performances comparable to the noble metal electrocatalysts.In the present work, transition metal phosphides were fabricated through a simple and costless codeposition-annealing process. Amorphous Ni-P and Co-P alloys were codeposited with red phosphorus particles and subsequently annealed. The annealing step was applied to promote the formation of intermetallics and the interdiffusion between pure phosphorus particles and the metallic matrix. As a result, different phase pure metal phosphides were obtained. The most important advantage of this methodology is the possibility to overcome the compositional limit typical of electrodeposited phosphorus-based alloys [2]. Elemental phosphorus codeposition allows to reach P concentrations higher than 50 % at., whereas simple Ni-P solid solution electrodeposition is compositionally limited to 25 % at. Enhancing P content is fundamental to obtain phosphorus rich compounds like Ni2P and Co2P, which are characterized by high catalytic activities for HER [3]. Another interesting benefit of the technique presented is the confinement of elemental P inside the coating during the annealing step. This peculiarity strongly optimizes material usage and it limits the presence of gaseous phosphorus, which is typical of many phosphorization processes used in literature to obtain metal phosphides [4] and it can result into the formation of the unstable white P allotrope.Specifically, Ni-P and Co-P were codeposited with red P particles and process conditions were optimized to maximize elemental P particles concentration. Annealing temperature and duration were varied to investigate their influence on final electrocatalytic perfrormances. Characterization techniques like XRD, SEM, EDS, cross-sectional analysis and XPS were used to determine phase composition of the materials obtained and to characterize their morphology. The electrocatalytic HER activity and stability of the different transition metal phosphides were tested in 0.5 M H2SO4. In all the cases, remarkable results were obtained, which matched up well with present existing literature where similar electrocatalysts have been fabricated through different methods [5]. The lowest overpotential was obtained in the case of Co-P/P codeposition and subsequent annealing at 290 °C: 62 mV vs. RHE at a current density of 10 mA/cm2 in 0.5 M H2SO4 solution.[1] P. Xiao et al., Adv. Energy Mater. 5, 1500985 (2015)[2] R. L. Zeller and U. Landau, J. Electrochem. Soc. 139(12), 3464 (1992)[3] A. R. J. Kucernak et al., J. Mater. Chem. A 2, 17435 (2014)[4] X. Wang et al., Angew. Chem. 54(28), 8188 (2015)[5] Z. Pu et al., Chem.Mater. 26(15), 4326 (2014)

Non-noble metal based broadband photothermal absorbers for cost effective interfacial solar thermal conversion

Abstract In recent years, noble metal-based solar absorbers have been extensively studied as their pronounced plasmonic resonances and high solar-to-thermal conversion efficiency. However, the high cost of noble metals is the unavoidable roadblock restricting the way towards scalability. In this work, we report a nickel-based photothermal absorbers, which is capable of realizing an average solar absorption of ∼97% in the range of 400–2500 nm originating from relatively weaker collective plasmonic resonances but more pronounced single electron excitation. Importantly, it is easily fabricated via the straightforward physical deposition and cost-effective with a raw material price of ∼0.3% gold and ∼20% of silver. We used it for interfacial solar vapor generation and realized an evaporation rate of ∼0.9 kg m−2 h−1 under one sun, almost comparable to the counterparts made from noble metals. The excellent performance combined with the cost effective and scalable fabrication process makes it be a promising candidate for mass off-grid solar desalination.

Heteroatom-Doped Carbon Materials for Hydrazine Oxidation.

The key in designing efficient direct liquid fuel cells (DLFCs), which can offer some solutions to society's grand challenges associated with sustainability and energy future, currently lies in the development of cost-effective electrocatalysts. Among the many types of fuel cells, direct hydrazine fuel cells (DHFCs) are of particular interest, especially due to their high theoretical cell voltages and clean emission. However, DHFCs currently use noble-metal-based electrocatalysts, and the scarcity and high cost of noble metals are hindering these fuel cells from finding large-scale practical applications. In order to replace noble-metal-based electrocatalysts with sustainable ones and help DHFCs become widely usable, great efforts are being made to develop stable heteroatom (e.g., B, N, O, P and S)-doped carbon electrocatalysts, the activities of which are comparable to, or better than, those of noble metals. Here, the recent research progress and the advancements made on the development of heteroatom-doped carbon materials, their general properties, their electrocatalytic activities toward the HzOR, and their dopant- and structure-related electrocatalytic properties for the HzOR are summarized. Perspectives on the different directions that the research endeavors in this field need to take in the future and the challenges associated with DHFCs are included.