Promising Green Energy Source Research Articles

A novel one-time unified configuration strategy with L-SHADE optimizer for enhanced power extraction in thermoelectric generator array

The thermoelectric generator (TEG) is a promising green energy source, converting wasted heat into electric power without relying on chemical reactions or emitting harmful substances. However, a significant challenge obstructing its practical deployment is the power losses due to nonuniform temperature distribution (NUTD) within its modules, particularly in applications like solar-TEGs and automotive systems. Studies in the literature have addressed this challenge by proposing dynamic reconfiguration approaches (DRAs) for TEG arrays to mitigate power losses under NUTD conditions. However, the main issue with these DRAs is their reliance on numerous switches and sensors, which increases the system’s cost and complexity and necessitates regular maintenance. To provide a cost-effective solution, this paper introduces an innovative approach to designing a One-time Unified Configuration (OUC) for TEG arrays as an alternative to the standard series–parallel (SP) arrangement. This approach formulates an optimization problem to establish OUC as a unique layout for the TEG array under multiple NUTDs. The L-SHADE optimizer is tailored to determine the OUC layout that fits multiple NUTDs simultaneously. The yielded OUC ensures a consistent temperature distribution among the parallel strings of the TEG arrays, thereby maximizing the overall power output. The proposed OUC is rigorously implemented and tested on both symmetrical (9 × 9) and asymmetrical (10 × 15) TEG arrays and compared with DRA. Additionally, it is validated through a hardware setup involving a (5 × 5) TEG array under varying NUTDs. The results demonstrate a remarkable enhancement in TEG array output power with gains exceeding 10% compared to the standard SP configuration. Furthermore, the OUC eliminates the need for switches and sensors, resulting in cost savings of approximately 1498.5$ and 2775$ for the (9 × 9) and (10 × 15) TEG arrays, respectively, compared to DRA.

ZnSe-doped N-C skeleton-driven electrode for enhanced electron transport in microbial fuel cells

Microbial fuel cells (MFCs), a promising green energy source, have faced limitations in performance. To address this, we synthesized a porous Zn-Se-N-C nanomaterial with a large specific surface area and significant defect density through the utilization of metal–organic frameworks (MOFs). Surface unique topography characteristics are tuned by controlling the annealing temperature. Density functional theory (DFT) calculations confirmed that the synergistic effect of Zn and Se in ZnSe nanoparticles can significantly improve oxygen reduction reaction (ORR) electrocatalytic activity. Experimental results demonstrated that the ORR performance of Zn-Se-N-C 1000 °C catalyst is comparable to that Pt/C catalyst in both alkaline and neutral conditions, especially in alkaline media. When employed as the cathode catalyst in asymmetrical MFCs with a neutral anode and an alkaline cathode, the Zn-Se-N-C 1000 °C(cathode)-MFC system achieved an impressive output current density of 8 ± 0.2 A/m−2 and a remarkable power density of 2000 ± 30 mW m−2. Additionally, the unique pore structure of Zn-Se-N-C1000°C made it highly suitable as an anode in MFCs. The Zn-Se-N-C 1000 °C (anode)-MFC demonstrated an output current density of 7.1 ± 0.9 A/m−2 and a power density of 3000 ± 111 mW m−2.

Plasma-assisted in situ engineering of bimetallic phosphate coated Ni(OH)2–CuO nanosheets for robust electrocatalytic hydrogen evolution

Hydrogen production by water electrolysis is a promising green and sustainable energy source, and engineering low-cost and high-efficiency electrocatalysts is crucial to ensure reliable and abundant global energy supply. Herein, a new and effective approach for electrocatalyst production for robust hydrogen evolution reaction (HER) is reported. The Ni–Cu hydroxide and oxide nanosheets are directly synthesized on the plasma-treated nickel foam (PNF) substrate, and then the ultrathin layer of transition metal phosphate is electrodeposited. The CuO and Ni(OH)2 heterostructures effectively enrich the catalytically active sites, reduce the HER free energy while greatly increasing the conductivity, thus causing the high HER activity. Meanwhile, the multilayer nickel-cobalt phosphate not only accelerates the HER reaction kinetics, but also acts as a protective layer, which greatly improves the electrode stability. The overpotential of the synthesized NiCo–P@CuO–Ni(OH)2/PNF catalyst is 59 mV (Tafel slope is 51.4 mV dec−1) for HER driven with a current density of 10 mA cm−2 (j10) in 1.0 M KOH electrolyte. Importantly, the nanostructure and sustainable activity of NiCo–P@CuO–Ni(OH)2 are retained after a 100 h HER process under the simulated industrial conditions. The Density Functional Theory and in situ Raman results reveal that the nickel sites exposed at the CuO–Ni(OH)2 heterointerface act as the HER catalytically active centers.

In-situ introduction of CePO4 for stabilizing electrocatalytic activity of quasi-MOF with partially missing C≡N skeleton

Hydrogen (H2) is considered one of the most promising green energy sources due to its high combustion heat value and non-polluting byproducts after combusting. Electrolysis of water to product H2 is a safe and stable way. Nevertheless, the current commercially available electrocatalysts suffer from high cost and slow reaction kinetics, hindering the widespread application of electrocatalytic water splitting. Metal-organic framework (MOF) have been concerned widespread as materials with high activity sites in the field of electrocatalyst. However, the presence of organic frameworks in MOF results in slow electron transfer rates and weak catalytic activity. To address this issue, this research has constructed a novel CePO4/quasi-MOF heterostructure with partial amorphous phase. The partial absence of organic frameworks in this heterostructure exposes more active metal sites, while the presence of the amorphous phase enhances the porosity of material. The overpotentials (η10) of CePO4/Ce-PBA-2 for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are 242 and 192 mV, respectively. The density functional theory (DFT) calculations demonstrate that constructing the CePO4/Ce-PBA-2 heterostructure with missing C≡N frameworks partially accelerates the electron transfer between metal ions, improving the reaction kinetics of HER and OER effectively. On the other hand, CePO4/Ce-PBA-2 exhibited a specific capacitance of 1346.7F g−1 at 1 A/g. The CePO4/quasi-MOF heterostructure achieves efficient electrocatalytic water splitting and energy storage in supercapacitors simultaneously. This study further paves the way for the application and development of MOF in the field of electrochemistry.

(Invited) Investigation on Dynamics of Expansion Forces and Dimensions Changes of the Pilot Scale Electrodialysis Stack

Electrodialysis (ED) represents a matured and well-established desalination and electromembrane separation technology with typical plate-and-frame configuration. In order to satisfy application demands, there is a trend for an increasing dimension and operating temperature of the industrial ED capable of high performance and efficiency in view of process time and system volume. These activities are motivated mainly by process cost reduction and exploiting new application fields benefiting from higher operating temperature and higher performance-to-volume ratio. This is also the case of reverse electrodialysis, currently meeting a growing popularity as a promising green energy source. However, experiences in a development of larger scale electromembrane devices show that scale-up from laboratory or pilot system to industrial ones is not straightforward. The scale-up simply based on increasing membrane active area or number of membranes, without appropriate modifications of entire unit design, often lead to accentuation of negative effects that are normally negligible on a small scale.One of the critical issues in larger scale represents dimensional changes of the ED stack, mainly due to membranes swelling and changes of mechanical properties of the stack materials as a respond to variation of operating conditions (temperature, electric current, salt concentration). When a robust rigid frame is used for stack assembly, such stack expansion may lead to an increase of the internal expansion forces causing irreversible mechanical damage of the materials used (membranes, spacers). On the contrary, the stack shrinking (e.g. due to membrane drying and deswelling) negatively affects the tightness. Consequently, the performance, reliability and lifetime of the apparatuses can be significantly exacerbated. Therefore, an autonomous (passive or active) system of compression force control has to be employed, which at each moment spontaneously adapts to stack dimensions keeping compression/expansion force at an optimal value. However, prior to a development of such system a deeper fundamental understanding of the stack behaviour is required. We are mainly interested at a) a qualitative and quantitative respond of the stack internal forces upon variation of different operating parameters, b) uniformity of distribution of internal expansion forces, c) dynamics (characteristic times) and reversibility of the stack dimensional changes, d) effect of different compression forces and stack compression-expansion cycles to longer-term operation of the stack and also e) stack tightness.In the first part of presented contribution the basic principle of electrodialysis process, system design and critical aspects of the ED process operation in industrial practice will be discussed. Next, the results of the research aimed at investigation of the dimensional and expansion forces changes in the pilot electrodialysis stack will be presented. The pilot-scale ED unit consists of 100 membrane pairs equipped by heterogeneous anion- and cation-selective membranes. Working area is of 0.4 × 0.1 m2. The stack is orientated horizontally assembled into the robust frame made of aluminum Item® profiles. A rigid endplate is attached to one side of the stack, whereas the opposite end-plate is segmented and equipped by 6 tensiometers measuring local stack expansion force. This compression force is applied to the stack by six pneumatic cylinders with equal pressure pressurized by a one standard compressor. The aspects of the stack behavior mentioned above are investigated as a dynamic respond of the stack to sudden changes in operating temperature (20 – 65 °C), electric current, salt concentration (0 – 160 g/dm3) and compression force (up to 45 kN). Different regimes are investigated: a) a regime with constant compression force in the pneumatic cylinders, or b) constant stack dimension (rigid compression frame) during the entire experiment. It was found that the effect of temperature was significantly more pronounced than the effect of salt concentration and electrical current. Moreover, up to 3 different characteristic times in the stack dynamic respond to temperature change were found.The financial support from grant agency of Ministry of Trade and Industry of the Czech Republic within program TRIO (project TOM2022 no. FV40053) is gratefully acknowledged.

Study on explosion characteristics of hydrogen in a sudden expansion pipe

ABSTRACT As a promising green energy source, the risk of hydrogen explosion cannot be ignored. In the industrial environment, the connection between factories and different regions may form a mutated structural space. This structure may have a significant impact on the consequences of hydrogen accidents, which is worthy of study. In this research, the simulation method is used to analyze the explosion and combustion process of hydrogen flame propagation in a sudden expansion pipe, which focuses on the impact of the cross-section ratio. The results indicate that due to the influence of Rayleigh-Taylor instability, the flow field in the dead zone near the sudden expansion structure can be unstable and generate vortices, which will significantly change the development of gas combustion and explosion. Under the extrusion and entrainment of vortices, the flame front structure is changed from finger-like flame to mushroom-like flame. When the flame enters the downstream pipe section through the expansion port, the impact of vortices on the flame propagation velocity is changed from suppression to excitation, and the excitation effect is closely related to the cross-section ratio. At the cross-section ratio μ = 3, the maximum flame propagation velocity and maximum pressure growth rate of the downstream pipe are 198.7 m/s and 53.12 MPa/s, respectively, which are 68.8% and 151.4% times higher than those in the case of the cross-section ratio μ = 1.5. There is a remarkable impact of sudden expansion structure on flame propagation and explosion overpressure.

Perovskite quantum dot-based tandem triboelectric-solar cell for boosting the efficiency and rain energy harvesting

Silicon (Si) solar cell efficiently convert solar energy into electricity under the sun illumination, but its inherent intermittent power generation due to diurnal and seasonal cycle has usually allowed for the requirement for alternative power sources. Owing to the abundance, diversity and availability, rain drop energy is one of the most promising green energy sources. Hence, hybrid energy harvesting could be a promising strategy of achieving preferential hybrid performances without sacrificing the advantages in individual devices. Herein, we proposed a hybrid solar and rain energy harvesting device featuring the integration of triboelectric nanogenerator (TENG) top-cell and a crystalline Si solar cell bottom-cell by laminating perovskite quantum dots-embedded polydimethylsiloxane composite film (PQDP) onto the Si solar cell, which endows enhanced electrical output performances under rainy days. To overcome the limitation of low external quantum efficiency (EQE) in the ultraviolet region of the Si solar cell, the PCE of the hybrid solar cell is significantly enhanced from 18.47% of bare Si solar cell to 20.16% owing to the anti-reflection effect of PQDP film and the down-conversion property of CsPbBr3 QDs doped with Ce3+ ions. Meanwhile, this hybrid solar cell presents excellent durability after continuous measurement over 7 days. This tandem hybrid solar cell provides a promising strategy to simultaneously scavenging the solar and rain energy and boosting the power conversion efficiency by introducing the perovskite QDs without affecting the efficiency of bare Si solar cell.

Ultrafast Preparation of Metal/Carbon Nanocomposite Electrocatalysts by Magnetic Induction Heating toward Efficient Hydrogen Evolution Reaction

Hydrogen, which can be readily produced by electrochemical water splitting, has been hailed as one of the most promising green energy sources. In a water electrolyzer, catalysts are needed for the hydrogen evolution reaction (HER) at the cathode, which are traditionally based on platinum-based materials. Recently, carbon-based nanocomposites have emerged as viable alternatives, which are mostly prepared by pyrolysis or wet chemistry methods, which are time- and energy-consuming. We have exploited magnetic induction heating (MIH) for ultrafast and green preparation of high-performance HER electrocatalysts. A novel MIH method was developed for the ultrafast and green preparation of carbon-supported Ru NPs toward HER in alkaline media, where the size and morphology of the Ru NPs can be readily manipulated by the heating current and duration. It is expected that MIH can be exploited for the design and engineering of high-performance nanocomposite catalysts for important electrochemical energy technologies.

Recent Update on anaerobic digestion of paddy straw for biogas production: Advancement, limitation and recommendations

At present, development and production of advanced green energy sources are highly demanded, and this may offer a clean and sustainable environment to our modern society. In this reference, biogas is emerging as a promising green energy source and seems to have high potential to replace fossil-fuel based energy sources in the coming future. Further, lignocellulosic biomass (LCB) based biogas production technology has been found to be highly promising owing to several advantages associated therewith. Rich inorganic content, renewable nature, huge availability and low-cost are the key beneficial factors of LCB-based feedstock l to produce biogas. Among the varieties of LCB, paddy straw is one of the most demanding feedstocks and is highly rich in organic compounds that are imperative to producing biogas. Nevertheless, it is noticed that paddy straw as a waste material is usually disposed-off by direct burning, whereas it exhibits low natural digestibility due to the presence of high lignin and silica content which causes severe environmental pollution. On the other hand, paddy straw can be a potential feedstock to produce biogas through anaerobic digestion. Therefore, based on the current ongoing research studies worldwide, this review evaluates the advancements made in the AD process. Meanwhile, existing limitations and future recommendations to improve the yield and productivity of the biogas using paddy straw have been discussed. The emphasis has also been given to various operational parameters developments, related shortcomings, and strategies to improve biogas production at pilot scale.

Spherical Triboelectric Nanogenerator Based on Eccentric Structure for Omnidirectional Low Frequency Water Wave Energy Harvesting

AbstractOcean wave energy is a promising green energy source, but it is difficult to exploit on a large scale due to its low frequency and the random uncertainty of its direction. In this study, a spherical eccentric structured triboelectric nanogenerator (Se‐TENG) is designed to harvest omnidirectional low‐frequency water wave energy. Power management circuits (PMM) are designed to optimize the utilization of water wave energy at low frequencies for large‐scale conversion and storage. It is found that the output performance of the Se‐TENG device is influenced by the frequency of the water waves, with the best output performance at a water wave frequency of 2.0 Hz, given that the wave amplitude is 9 cm. It is verified that within the Se‐TENG, the parallel connections of eccentric structured triboelectric nanogenerators (E‐TENGs) are more conducive to energy storage and conversion. In addition, the Se‐TENG used in conjunction with an energy storage device is able to successfully power light‐emitting diodes (LEDs) and digital thermometers, demonstrating its ability to harvest low‐frequency water wave energy in random directions. The unique structure of the Se‐TENG offers an innovative and effective way of gathering blue energy on a large scale.

Research Progress in the Preparation of Phosphor for White Light Emitting Diode

As a solid-state lighting source, white light emitting diode (LED) has become the most promising green lighting energy source in the 21st century with its three advantages of energy-saving, environmentalfriendly and green-oriented. The study summarized the research progress in the preparation of phosphor for white light emitting diode, analyzed and compared the effects of different materials and synthesis methods on its luminescence performance. The future development trend was also prospected.

(Invited) Current Density Distribution In a Pilot-Scale Electrodialysis Unit - 3D Mathematical Modeling and Experimental Investigation

Electrodialysis (ED) represents a matured and well-established desalination and membrane separation technology. In order to satisfy application demands, there is a trend for increasing dimensions of not only the industrial ED, but also of the other electrochemical membrane units, like electrolyzers, fuel cells etc.), capable of high process intensity and efficiency. These activities are driven mainly by cost reduction. This is also the case of reverse electrodialysis as an allied process, currently meeting rapidly growing popularity as a promising green energy source. However, experiences in a development of larger scale membrane electrochemical devices document scale-up from laboratory or pilot system to industrial ones not to be straightforward. The scale-up based on an direct increase of smaller devises dimensions, like e.g. increasing membrane active area or number of membranes without appropriate modifications of entire unit design, often leads to pronounced nonuniformity of local current density, mass and heat distribution inside the system. Consequently, the performance, reliability and lifetime of industrial scale apparatuses is significantly exacerbated. A uniformity of the above-mentioned fluxes distribution strongly depends on numerous aspects, particularly on the geometry of electrodes, manifolds and fluid distributors. Due to these facts, there is an urgent need of fundamental understanding of the relations between the system geometry and uniformity of the fluxes, especially on an industrial scale.The presented work focuses at investigation on local current density distribution in the pilot-scale ED unit consisting of 200 vertically orientated membrane pairs with working area of 0.64 × 0.32 m2 per membrane. Planar-plate electrodes are horizontally segmented into the 6 identical and electrically insulated segments allowing determination of current distribution along main direction of the solutions flow. The current distribution is investigated at different operating conditions (salt concentration, applied current, solution flow rate, electrode compartment solutions properties etc.). In parallel, a macrohomogeneous (volume-averaged) 3D mathematical model is validated and employed to calculate and visualize the local fields of electric potential, current density and salt concentrations. A nonuniformity in the current distribution mainly due to the by-pass current through the manifold is observed. The qualitative relationships between the nonuniformity of current density distribution and process performance and reliability observed for pilot- or industrial-scale can be generalized to be valid also for other similar electromembrane systems with plate-and-frame design.

Bimetallic PtPd nanoparticles relying on CoNiO2 and reduced graphene oxide as a most operative electrocatalyst toward ethanol fuel oxidation

Of late, fuel cells have drawn great attentions owing to high-energy demands, fossil fuel depletion and worldwide environmental pollution. Direct ethanol fuel cell (DEFC) constituted as one of the most promising sources of green energy, howbeit the ethanol oxidation reaction (EOR) sluggish kinetic is one of the essential challenges toward the commercialization of DEFCs. Herein, we introduce bimetallic catalyst on CoNiO2 modified reduced graphene oxide (rGO) to completely exploit the advantages of nano-surface structures as well as the reduction of Pt and Pd loading in fuel cells. With the combined advantages of PtPd, CoNiO2 and rGO, a significant enhancement in electrocatalytic behavior, stability and CO poisoning tolerance of PtPd have been observed. Regarding the implications, PtPd/CoNiO2/rGO is greatly preferable than Pt/CoNiO2/rGO and Pd/CoNiO2/rGO in terms of high electroactive surface area (ECSA), electro-catalytic activity, and lower onset potential (Eons) towards the EtOH oxidation in alkaline media. Furthermore, the chronoamperometry curve (CA) illustrated 77% after 3600 s which is dramatically soared compared with the other electrodes (≤40%), demonstrating the high stability of the PtPd bimetallic nanoparticle electrocatalyst. Ultimately, PtPd/CoNiO2/rGO nanocomposite is found to be an excellent anode electrocatalyst for application in DEFCs.

Upgrading of Bio-Oil Model Compounds and Bio-Crude into Biofuel by Electrocatalysis: A Review.

Limited availability of fossil energy and serious environmental pollution have caused the emergence of bio-oil, which can serve as an alternative and promising green energy source. However, bio-oil generated from the rapid pyrolysis of biomass cannot be utilized immediately owing to its corrosivity, instability, and low heating value. Herein, the electrocatalytic hydrogenation (ECH) process towards bio-oil upgrading is reviewed. Specifically, the ECH integrates the advantages of mild operating conditions, no petrochemically derived hydrogen and good controllability. The influence of different factors on the conversion of bio-oil components and product selectivity in the ECH process are presented comprehensively. In addition, various reaction mechanisms are discussed in the designed ECH systems. Finally, some challenges need to be further overcome for real bio-oil reduction in the ECH process: exploration of efficient multifunctional electrocatalysts for specific bio-oil components and determination of the dominant steps in the complicated reaction path network.

Optimal load scheduling for off-grid photovoltaic installations with fixed energy requirements and intrinsic constraints

Solar energy is one of the most promising green energy sources. On-grid photovoltaic installations supply energy to consumers as a support energy source, but in isolated areas, it comes as the unique source. The decision-maker must dimension the installation, maintaining system performance with reasonable investments. In some scenarios, the utility manager can handle the energy delivered to consumers as every subsystem can be independently connected. A strategy for scheduling the energy consumption to decrease the number of photovoltaic modules required in a standalone system is proposed here. The problem formulation corresponds to generalising a more specific problem before published. We presented a real case study being the groups of hydrants that provide water to crops in a pressurized irrigation system for energy consumption to schedule.

Local hot charge density regulation: Vibration-free pyroelectric nanogenerator for effectively enhancing catalysis and in-situ surface enhanced Raman scattering monitoring

Abstract Highly efficient catalysis and monitoring play an extremely important role in the modern chemical industry. The local thermal charge density, which is proportional to the square of the local near-field enhancement, is essential to improve the catalytic efficiency. However, the vibration-free way to improve the local hot charge density at the surfaces of the catalyst still needs to be investigated. Optical energy is one of the most promising green energy sources in the natural environment. Here, we designed a pyroelectric nanogenerator by absorbing optical energy as surface enhanced Raman scattering (SERS) substrate for in-situ monitoring the complete oxidation reaction from 4-aminothiophenol (4-ATP) to 4-nitrothiophenol (4-NTP) and the oxygen reduction reaction (ORR) intermediates. The pyroelectricity could be easily generated by the simulated sunlight illumination and was investigated in theory and experiment. The electric field induced by the coupling of pyroelectric and plasmonic effect can effectively tune the hot charge density on the surface of SERS substrate, which further increases the SERS signals and efficiently drives the catalytic process. The proposed measuring strategies of catalytic and SERS enhancement can promote energy conservation and environmental protection.

Intensified reactive distillation configurations for production of dimethyl ether

The combustion properties of dimethyl ether (DME) are similar to the conventional fuels; hence it is being used as a promising green energy source. The conventional method of DME production by methanol dehydration is highly energy consuming due to the use of a series of distillation columns. In the present study, an energy efficient reactive distillation configuration is proposed for DME production which leads to higher methanol conversion with less energy requirement as compared to reported configurations. The reactive distillation (RD) and dual reaction zone reactive divided wall column (RDWC) were analyzed using steady state ASPEN simulations. Subsequently, all the design parameters were optimized by sensitivity analysis to minimize the Total Annual Cost (TAC) of the configuration. The results showed that the RD column is more energy efficient than RDWC as it requires 10.68 % less TAC. The proposed RD and dual reaction zone RDWC configurations were found to have less specific energy requirements and less cost per kg of DME than any other configuration reported earlier.

Enhancing charge transfer for ZnO nanorods based triboelectric nanogenerators through Ga doping

Triboelectric nanogenerator (TENG) has been developed as a promising green energy source, but the working mechanism as regard to the surface condition in charge transfer is still under investigation. Therefore, the work is devised to study the charge transfer efficiency by varying electron concentration at the surface of ZnO nanorods (NRs) arrays through Ga doping as a means to change surface chemistry of a given material when rubbing with PDMS and nylon. The hydro-thermally grown ZnO NRs arrays remain vertically aligned upon Ga doping from 0.18 to 0.69 at%, effectively generating free electron concentrations from 2.63× 1014 to 1.80× 1018 cm−3, compared to 4.24 × 1016 cm−3 corresponding to the un-doped ZnO NRs. The triboelectric output voltage, current density and tribo-charges density of the Ga-doped ZnO NRs are remarkably enhanced by up to ~13, ~90 and ~15 times, respectively, compared to the un-doped ZnO NRs. This work verifies the concept of n-type semiconductors in favor of transferring electrons to the counter materials bound to receiving electrons such as PDMS in the triboelectric series and vice versa to the materials bound to donating electrons such as nylon. This behavior is mainly ascribed to the work function difference in proposed band diagrams with surface band bending as well as the kinetic constraints to the ease of charge transfer. This work not only deepens the understanding into the fundamental charge transfer mechanism governing the triboelectrification efficiency but provides a facile method to maximize the range of positions in the triboelectric series for a given semiconductor to optimize device design for TENG.

Doubling the thermoelectric power factor of earth abundant tin nitride thin films through tuned (311) orientation by magnetron sputtering

Thermoelectricity has been considered a promising green energy source for mankind. This method of energy generation poses challenges due to scarcity of the constituent elements of the efficient thermoelectric materials. The development of high performance materials for thermoelectric generation is limited with the co-responsive nature of transport parameters. In this work, earth abundant tin nitride (Sn3N4) thin films were deposited by reactive radio frequency magnetron sputtering and investigated its thermoelectric response. The electron bands of the prepared thin films were actively aligned to optimize the trade-off between the Seebeck coefficient and electrical conductivity for the enhancement of power factor (S2σ). The reduction in nitrogen gas pressure of reactive sputtering reduced both working pressure and the amount of reactive nitrogen. This experimental approach of combined effect introduced preferred orientation (PO) and stoichiometric variations simultaneously in the fabricated thin films. The increased scattering associated with preferred orientation and increased carrier concentration associated with stoichiometric variations converged the conduction band along with shifting of Fermi energy toward the conduction band minimum. The engineered band structure of tin nitride thin film realized over 2-fold hike in power factor up to 390 μW/m-K2 at 250 °C with a Seebeck coefficient of −144 μV/K and resistivity of 53.11 μΩ-m. This study reveals the potential nature of the earth abundant nitrides in the field of renewable energy generation. The experimental strategy adopted in this study provides an alternative approach to engineer the band structure of a thin film for optimized transport parameters.

Holey Ni-Cu phosphide nanosheets as a highly efficient and stable electrocatalyst for hydrogen evolution

Hydrogen, generated by electrocatalytic process, is one of the most promising sources of green and sustainable energy. Herein, we report a novel elctrocatalyst for hydrogen evolution reaction (HER) fabricated by doping Ni foam (NF) supported Ni2P nanosheets with Cu atoms. The Cu atoms effectively tune the structure and physicochemical properties of Ni2P, leading to the lower HER free energy, improved electrical conductivity, and high exposure of surface active sites. The optimized Ni1.8Cu0.2-P displays an excellent catalytic performance and stability, which is demonstrated by the low overpotentials of 78 (Tafel slope: 70 mV dec-1) and 245 mV to reach a current density of 10 and 100 mA cm-2 for the HER in 1.0 M KOH. The high electrocatalytic activity of Ni1.8Cu0.2-P is attributed to the increased Fermi level and the exposed active crystal plane (201). The H2 amount produced with a current density of 10 mA cm-2 is about 1.91 mmol h-1 cm-2, which is the highest value among the reported non-precious metal catalysts.