Thermodynamic Potential Research Articles

Dynamic modelling of a compressed heat energy storage (CHEST) system integrated with a cascaded phase change materials thermal energy storage

Carnot batteries represent an emerging thermo-mechanical energy storage technology based on the conversion of surplus electricity into medium–low temperature heat, and subsequent conversion of the heat into electricity. A promising Carnot battery’s configuration is the Compressed Heat Energy Storage (CHEST) that combines a high-temperature heat pump (charge phase), an Organic Rankine Cycle (discharge phase) and a thermal energy storage (TES) system. As of now, all the literature studies on CHEST were designed to store the thermal energy into a cascaded TES combining a pressurized water storage for the sensible section and latent heat material for the evaporation and condensation sections. The objective of the present work is to numerically investigate a novel configuration of the TES system utilizing a cascade of multiple phase change materials (PCMs) in place of the cascade of sensible heat and phase change materials presented in literature, aiming to enhance both the energy density and the round trip efficiency of the system. The comparative technical analysis has been carried out by developing for the first time a dynamic numerical model of the CHEST system. Indeed, while the current literature studies on CHEST are only focused on preliminary analyses to define the general thermodynamic potential and to identify the limits of the overall system, this paper overcomes this gap and presents a detailed dynamic analysis of the CHEST with focus on TES modelling. Notably, the authors developed a plant model in MATLAB that blends together algebraic and differential sub-models detailing the transient behaviour of the CHEST system. The results are of interest for academia and industry and contribute significantly to the development of a more efficient CHEST system. Indeed, by enhancing the thermal buffer effect typical of PCM media, the cascaded TES augments both the COP of the high-temperature heat pump (4.13 vs 3.79) and the electric efficiency of the ORC (11.69 % vs 11.31 %). As a result, the novel CHEST system based on cascaded PCMs is capable to achieve a round trip efficiency of 47.6 % and an energy density of 6.9 kWhe/m3, simultaneously increasing the respective values of the state-of-the-art solution by 13 % and 100 %, respectively.

Open-circuit and short-circuit loss management in wide-gap perovskite p-i-n solar cells

In this work, we couple theoretical and experimental approaches to understand and reduce the losses of wide bandgap Br-rich perovskite pin devices at open-circuit voltage (VOC) and short-circuit current (JSC) conditions. A mismatch between the internal quasi-Fermi level splitting (QFLS) and the external VOC is detrimental for these devices. We demonstrate that modifying the perovskite top-surface with guanidinium-Br and imidazolium-Br forms a low-dimensional perovskite phase at the n-interface, suppressing the QFLS-VOC mismatch, and boosting the VOC. Concurrently, the use of an ionic interlayer or a self-assembled monolayer at the p-interface reduces the inferred field screening induced by mobile ions at JSC, promoting charge extraction and raising the JSC. The combination of the n- and p-type optimizations allows us to approach the thermodynamic potential of the perovskite absorber layer, resulting in 1 cm2 devices with performance parameters of VOCs up to 1.29 V, fill factors above 80% and JSCs up to 17 mA/cm2, in addition to a thermal stability T80 lifetime of more than 3500 h at 85 °C.

Contact and metric structures in black hole chemistry

We review recent studies of contact and thermodynamic geometry for black holes in AdS spacetimes in the extended thermodynamics framework. The cosmological constant gives rise to the notion of pressure P = −Λ/8π and, subsequently a conjugate volume V, thereby leading to a close analogy with hydrostatic thermodynamic systems. To begin with, we review the contact geometry approach to thermodynamics in general and then consider thermodynamic metrics constructed as the Hessians of various thermodynamic potentials. We then study their correspondence to statistical ensembles for systems with two-dimensional spaces of equilibrium states. From the zeroes and divergences of the curvature scalar obtained from the metric, we carefully analyze the issue of ensemble non-equivalence and show certain complimentary behaviors in the description of a thermodynamic system. Following a thorough analysis of the familiar van der Waals system, we turn our attention to black holes in extended phase space. Considering the example of charged AdS black holes, we discuss the generic features of their thermodynamic geometry in detail. The relationship of the thermodynamic curvature(s) with critical points as well as microscopic interactions in black holes is also briefly explored. We finally set up the thermodynamic geometry for finite temperature gauge theories dual to black holes in AdS via holographic correspondence and comment on recent progress.

Thermodynamic restrictions determine ammonia tolerance of methanogenic pathways in Methanosarcina barkeri

Ammonia is a ubiquitous potential inhibitor of anaerobic digestion processes, mainly exhibiting inhibition towards methanogenic activity. However, knowledge as to how ammonia affects the methanogens is still limited. In this study, we cultured a multitrophic methanogen, Methanosarcina barkeri DSM 800, with acetate, H2/CO2, and methanol to evaluate the influence of ammonia on different methanogenic pathways. Aceticlastic methanogenesis was more sensitive to increased ammonia concentrations than hydrogenotrophic and methylotrophic methanogenesis. Theoretical maximum NH3 tolerances of M. barkeri fed with acetate, H2/CO2, and methanol were calculated to be 39.1 ± 9.0, 104.3 ± 7.4, and 85.7 ± 1.0 mg/L, respectively. The order of the ΔG range of M. barkeri under three methanogenic pathways reflected the order of ammonia tolerance of M. barkeri. Our results provide insights into the role of the thermodynamic potential of methanogenesis on the tolerance of ammonia stress; and shed light on the mechanism of ammonia inhibition on anaerobic digestion.

Liquid Water: A Single Approach to Its Two Continuous Phase Transitions

In this paper, we show that both continuous phase transitions of liquid water, the liquid-gas and the liquid-liquid, can be articulated within a single thermodynamic analytical formalism. This result follows from a combination of the two-liquid model (TLM), recently confirmed for water, with the idea of a thermal-dependent excluded volume, ve, concept introduced by van der Waals, in his famous state equation. Starting from the fundamentals of thermodynamics, it will be shown that the TLM naturally leads to the idea of an extensive thermal-dependent ve that acts as a parameter of the sample thermodynamic potentials. This procedure effectively separates the thermodynamics of the system into two parts: the first concerns the clusters' thermodynamics, taken as wandering particles, and the second concerns the thermal behavior of its internal structure (geometry and number of particles). From this result, we demonstrate that the condition of mechanical instability leads to not one but two critical points, each happening in one of the above-described parts of the system.

Solar-Light-Responsive Zinc-Air Battery with Self-Regulated Charge-Discharge Performance based on Photothermal Effect.

It is extremely challenging to significantly increase the voltaic efficiency, power density, and cycle stability of a Zn-air battery by just adjusting the catalytic performance of the cathode with nanometers/atomistic engineering because of the restriction of thermodynamic equilibrium potential. Herein, inspired by solar batteries, the S-atom-bridged FeNi particles and N-doped hollow carbon nanosphere composite configuration (FeNi-S,N-HCS) is presented as a prototype of muti-functional air electrode material (intrinsic electrocatalytic function and additional photothermal function) for designing photoresponsive all-solid-state Zn-air batteries (PR-ZABs) based on the photothermal effect. The local temperature of the FeNi-S,N-HCS electrode can well respond to the stimuli of sunlight irradiation because of their superior photothermal effect. As expected, under illumination, the power density of the as-fabricated PR-ZABs based on the FeNi-S,N-HCS electrode can be improved from 77 mW cm-2 to 126 mW cm-2. Simultaneously, charge voltage can be dramatically reduced, and cycle lifetime is also prolonged under illumination, because of the expedited electrocatalytic kinetics, the increased electrical conductivity, and the accelerated desorption rate of O2 bubbles from the electrode. By exerting the intrinsic electrocatalytic and photothermal efficiency of the electrode materials, this research paves new ways to improve battery performance from kinetic and thermodynamic perspectives.

Automated discovery of generalized standard material models with EUCLID

We extend the scope of our recently developed approach for unsupervised automated discovery of material laws (denoted as EUCLID) to the general case of a material belonging to an unknown class of constitutive behavior. To this end, we leverage the theory of generalized standard materials, which encompasses a plethora of important constitutive classes including elasticity, viscosity, plasticity and arbitrary combinations thereof. We show that, based only on full-field kinematic measurements and net reaction forces, EUCLID is able to automatically discover the two scalar thermodynamic potentials, namely, the Helmholtz free energy and the dissipation potential, which completely define the behavior of generalized standard materials. The a priori enforced constraint of convexity on these potentials guarantees by construction stability and thermodynamic consistency of the discovered model; balance of linear momentum acts as a fundamental constraint to replace the availability of stress–strain labeled pairs; sparsity promoting regularization enables the automatic selection of a small subset from a possibly large number of candidate model features and thus leads to a parsimonious, i.e., simple and interpretable, model. Importantly, since model features go hand in hand with the correspondingly active internal variables, sparse regression automatically induces a parsimonious selection of the few internal variables needed for an accurate but simple description of the material behavior. A fully automatic procedure leads to the selection of the hyperparameter controlling the weight of the sparsity promoting regularization term, in order to strike a user-defined balance between model accuracy and simplicity. By testing the method on synthetic data including artificial noise, we demonstrate that EUCLID is able to automatically discover the true hidden material model from a large catalogue of constitutive classes, including elasticity, viscoelasticity, elastoplasticity, viscoplasticity, isotropic and kinematic hardening.

Facet-Dependent Photocatalytic Behavior of Fe-soc-MOF for Carbon Dioxide Reduction.

Exposing different facets on metal-organic frameworks (MOFs) is an efficient approach to regulate their photocatalytic performance for CO2 reduction. Herein, Fe-soc-MOFs exposed with different facets were successfully synthesized, and the morphologies of Fe-soc-MOF exposed with eight {111} facets (Fe-soc-O) and that exposed with eight {111} and six {100} crystal facets (Fe-soc-M) are first reported. Fe-soc-MOFs have facet-dependent active sites on their surface and correspondingly different catalytic performance for photocatalytic CO2 reduction. Fe-soc-O has the highest CO production of 1804 μmol g-1 h-1, while the Fe-soc-MOF exposed with six {100} facets (Fe-soc-C) has the best CO selectivity of 94.7%. Density functional theory (DFT) calculations demonstrate that the (111) facet has more favorable thermodynamic potential for CO2 reduction and H2 evolution compared with the (100) one, deriving from its facet-dependent active sites. This work shows that utilizing the facet-engineering strategy to regulate the active sites exposed on the surface of MOFs is feasible. The results display the relation between the facet of MOFs and the photocatalytic behavior for CO2 reduction.

Long-range Multiparticle Interactions Induced by Neutrino Exchange in Neutron Star Matter

Forces with a large radius of interaction can have a significant impact on the equation of state of matter. Low-mass neutrinos generate a long-range potential due to the exchange of neutrino pairs. We discuss a possible relationship between the neutrino masses, which determine the interaction radius of the neutrino-pair exchange potential, and the equation of state of neutron matter. Contrary to previous statements, the thermodynamic potential, when decomposed into the number of neutrino interactions, vanishes in any decomposition order, except for the interaction of two neutrons. In the one-loop approximation, long-range multiparticle neutrino interactions are stable in the infrared region for all neutrino masses and do not affect the equation of state of neutron matter or the stability of neutron stars.

Advanced electrocatalytic redox processes for environmental remediation of halogenated organic water pollutants.

Halogenated organic compounds are widespread, and decades of heavy use have resulted in global bioaccumulation and contamination of the environment, including water sources. Here, we introduce the most common halogenated organic water pollutants, their classification by type of halogen (fluorine, chlorine, or bromine), important policies and regulations, main applications, and environmental and human health risks. Remediation techniques are outlined with particular emphasis on carbon-halogen bond strengths. Aqueous advanced redox processes are discussed, highlighting mechanistic details, including electrochemical oxidations and reductions of the water-oxygen system, and thermodynamic potentials, protonation states, and lifetimes of radicals and reactive oxygen species in aqueous electrolytes at different pH conditions. The state of the art of aqueous advanced redox processes for brominated, chlorinated, and fluorinated organic compounds is presented, along with reported mechanisms for aqueous destruction of select PFAS (per- and polyfluoroalkyl substances). Future research directions for aqueous electrocatalytic destruction of organohalogens are identified, emphasizing the crucial need for developing a quantitative mechanistic understanding of degradation pathways, the improvement of analytical detection methods for organohalogens and transient species during advanced redox processes, and the development of new catalysts and processes that are globally scalable.

Research of the spent drying agent parameters in the mine grain dryer

Purpose. Improving the energy efficiency of the technological process of grain drying by reducing emissions of thermal energy with the spent drying agent by regulating the thermodynamic potential of the drying agent stream in the grain stream. Methods. To obtain and process the results, methods of engineering, programming, cybernetics, graphical and regression analysis and synthesis using a calculator and applications Matlab and Speq were used. Results. A set of equipment for monitoring the thermodynamic parameters of the technological process of grain drying was developed, manufactured and implemented at an operating mine grain dryer. The data of primary accounting of the results of experimental studies on the existing shaft grain dryer of heat and humidity indicators of the spent drying agent at different stages of grain drying were obtained. The energy aspects of increasing the efficiency of using the drying agent in the technological process of grain drying are considered. Conclusions 1. Due to the characteristics of primary measuring converters together with the means of display and archiving of indicators, the developed set of equipment for the control of the thermodynamic parameters of the technological process of drying grain is useful tool for the dryer operator, which cares for the quality of the finished product and energy saving of production. 2. The rational adjustment of the thermodynamic parameters of the drying agent stream provides a reduction in the energy consumption for drying about 6 %. 3. The results of the work can be used in further scientific research on the modernization of operated grain dryers and for the design of innovative energy-saving grain drying processes. Keywords: grain, drying agent, enthalpy, drying, automation, energy saving.

In situ Raman investigation of the femtosecond laser irradiated NiFeOOH for enhanced electrochemical ethanol oxidation reaction

Electrochemical ethanol oxidation reaction (EOR) is one of the promising reactions to replace oxygen evolution reaction (OER) in overall water splitting due to its lower thermodynamic equilibrium potential and non-poisonous reactant. However, the reaction mechanism and the electrocatalyst evolution of EOR remain unclear, especially for non-precious metal based electrocatalysts. In this work, the femtosecond laser assisted electrodeposition method is used for the preparation of electrocatalysts with different phase compositions of NiFeOOH. Detailed electrochemical studies and in situ Raman spectra indicate that EOR and OER possess different reaction pathways. Neither β-NiOOH or γ-NiOOH shows structural evolution before EOR, indicating the initial phase is the active phase for EOR. Between them, the γ-NiOOH shows more benign intrinsic activity towards EOR. However, for OER, both of β-NiOOH and γ-NiOOH would undergo a structural evolution before OER, that is the pre-catalysis process. The OER catalytic performance is determined by the final phase component and the density of active sites after the pre-catalysis process. This work takes full advantage of electrochemical methods and in situ Raman spectroscopy, and finds out mechanism differences between EOR and OER to guide further catalyst design.

New Pyrochlore-like Oxyfluorides Na2–2xSnxM2O5F2 (M = Nb5+ or Ta5+ and 1 ≤ x ≤ 0) as Potential Candidates for Overall Water Splitting Photocatalysis

Lone pair containing oxyfluorides have recently emerged as efficient and stable photocatalysts for overall water splitting (OWS). In this work we have obtained several new potential OWS photocatalysts with pyrochlore structure (i.e., Na2–2xSnxM2O5F2 with M = Nb5+ or Ta5+ and 1 ≤ x ≤ 0) through kinetically controlled ion-exchange reaction from Na2M2O5F2. Rietveld refinement of the structures as well as DFT indicate the Sn2+ lone pair stereochemical activity. The partial density of states reveals contributions at the top of the valence band that are mainly composed of a Sn 5s–Sn 5p hybridization through the (O,F) 2p orbitals. This leads to a significant narrowing of the band gap and an improvement of the photoconduction response by a factor ca. 50 with respect to the x = 0 compound, Na2Nb2O5F2. The Mott–Schottky measurements show that all materials possess band edge positions encompassing the thermodynamic redox potential of H+/H2 and O2/H2O. However, the valence band of SnNb2O5F2 may not be oxidative enough to overcome the overpotential associated with the O2– oxidation and hence could be unsuitable for OWS photocatalysis in contrast with Na1.5Sn0.25Nb2O5F2.

Volume effects on the QCD critical end point from thermal fluctuations within the super statistics framework

We investigate the impact of the finite volume and the thermal fluctuations on the Critical End Point of the QCD phase diagram. To do so, we implement the super statistics framework with Gamma, $F$, and log-normal distributions and their relation with the Tsallis non-extensive thermodynamics. We compute an effective thermodynamic potential as a function of the inverse temperature fluctuations and explicit dependence on the system volume. To find an analytic expression for the effective potential, we expand the modified Boltzmann factor by using the equilibrium thermodynamic potential computed in the Linear Sigma Model coupled to quarks. We find that the pseudo-critical temperature of transition at vanishing baryon chemical potential is modified by the size of the system being about $7\%$ lower for small volumes. Additionally, the critical endpoint moves to higher densities and lower temperatures (about $12\%$ in both cases). Interestingly, the results are quantitatively the same when the parameter that models the out-of-equilibrium situation is modified, indicating that the chiral symmetry restoration is robust against the thermal fluctuations in this approximation.

Heterogeneous Ni-MoN nanosheet-assembled microspheres for urea-assisted hydrogen production

Electrocatalytic water splitting is a promising technology for sustainable hydrogen (H2) production; however, it is restricted by the kinetically sluggish anodic oxygen evolution reaction (OER). Replacing OER with urea oxidation reaction (UOR) with low thermodynamic potential can simultaneously improve the energy efficiency of H2 production and purify urea-containing wastewater. Here we report a facile assembly-calcination two-step method to synthesize heterogeneous Ni-MoN nanosheet-assembled microspheres (Ni-MoN NAMs). The nanosheet-assembled structure and the synergistic metallic Ni-MoN heterogeneous interface endow the Ni-MoN NAMs with good OER (1.52 V@10 mA cm−2), UOR (1.28 V@10 mA cm−2), and hydrogen evolution reaction (HER, 0.16 V@10 mA cm−2) activity. The two-electrode urea electrolysis cell with Ni-MoN NAMs as both the cathode and anode requires an extremely low cell voltage of 1.41 V to afford 20 mA cm-2, which is 0.3 V lower than that of the water electrolyzer, paving the way for energy-saving H2 production.

Study of thermodynamics of a thermal electron in scattering

This work presents the study of the thermodynamic properties of thermal electrons participating in scattering events. This is necessary because scattering with a thermal electron in presence of a laser field was not studied yet and it reduces the complexity of event measurement (differential cross-section). To study thermodynamic properties, the authors model the thermal Hamiltonian in presence of a laser field and used it to study the thermodynamic properties using the partition function. The study shows thermodynamic energy, around the target with distance at field amplitude 0.1 a.u. to 0.9 a.u. has destructive interference, above field amplitude 1 a.u. to 2.5 a.u. has superposition and at field amplitude 2.5 a.u. and 3 a.u. have coulomb potential like nature. Also, thermodynamic energy with temperature was found constant except at field amplitude 2.5 a.u. and at field amplitude 2.5 a.u. destructive interference at 10 °C and 21 °C. The thermodynamical potential at field amplitude 0.1 to 3.5 a.u. found constant and above field amplitude 3.5 a.u. increased linearly when studied with respect to temperature at 10 Å. The thermal Hamiltonian increase sharply when thermal electrons enter in 1–5 Å, slowly in 5–10 Å and beyond 10 Å constant, and the thermal Hamiltonian nature is like coulomb potential.

Prediction of electronic and optical properties of monoclinic 1T’-phase OsSe2 monolayer using DFT principles

Following the discovery and characterization of transition metal dichalcogenides (TMDs) monolayers, which has created interest in last few years, it would seem natural to explore new possibilities of monolayers. Thus, using the density functional theory (DFT), we investigated the structural, electronic, vibrational and thermodynamic properties, and optical absorption of osmium selenide monolayer (monoclinic 1T’-phase OsSe 2 monolayer). We perform the calculations using the approaches based on the generalized gradient (GGA) and the local density (LDA) approximations for the optimized structure with the minimum energy, as well as we use the hybrid exchange–correlation functional HSE06 recommended in the literature for bandgap energy estimation. An indirect bandgap E g = 0 . 85 eV, E g = 0 . 95 eV and E g = 1 . 80 eV was obtained within the LDA-CAPZ, GGA-PBE and HSE06 level of calculation, respectively. The vibrational normal modes, infrared and Raman spectra were obtained and assigned in the frequency range of 0 − 400 c m − 1 together with the phonon dispersion relation. In addition, the optical absorption was shown to be sensitive to the plane of polarization of the incident light mainly in the range of UV radiation. The thermodynamic potentials and specific heat at constant volume were calculated and analyzed. These results indicated that the monoclinic 1T’-phase OsSe 2 structure could be potentially synthesized and bringing new potential technological applications.

Low-symmetry ferroelectric phases stabilized by anisotropic misfit strain

The complete thermodynamic potential of (111) ferroelectric thin films including anisotropic in-plane misfit strain, in-plane shear strain, and external stress is developed based on the Landau-Ginzburg-Devonshire thermodynamic theory. Anisotropic strain-tuned low-symmetry equilibrium phases in (111) single-domain ferroelectric $\mathrm{PbTi}{\mathrm{O}}_{3}$ films were investigated via the developed nonlinear thermodynamic potential and the misfit strain--misfit strain phase diagram was constructed. It was found that the anisotropic epitaxial strain can effectively control the orientations of polarization vectors, which determine the symmetry of equilibrium phases, and their functionalities. In particular, two types of low-symmetry triclinic phases, disappearing under isotropic strain states, can be stabilized by anisotropic strains. Low-symmetry monoclinic and triclinic ferroelectric phases and field-induced phase transitions were also analyzed in depth. It was indicated that the monoclinic (${M}_{A}^{1}$) symmetry rhombohedral-like--tetragonal-like transition and triclinic (${T}_{\mathrm{r}}^{1}$)-monoclinic (${M}_{B}^{1}$) phase transition would give rise to the superior piezoelectric properties as compared to other structure phase transitions. Electric field-enhanced piezoelectric response in triclinic structure originates from the elastic softening that is related to the shear ${u}_{5}$. These results provide guidance for interpreting and understanding more experimental observations as well as the designing of high-performance piezoelectric films.

A New Partially Phosphorylated Polyvinyl Phosphate-PPVP Composite: Synthesis and Its Potentiality for Zr (IV) Extraction from an Acidic Medium

A newly synthesized partially phosphorylated polyvinyl phosphate derivative (PPVP) was functionalized to extract Zirconium (IV) from Egyptian zircon sand. The specifications for the PPVP composite were approved effectively via different techniques, namely, FT-IR, XPS, BET, EDX, TGA, 1H-NMR, 13C-NMR, GC-MS, XRD and ICP-OES analyses, which demonstrated a satisfactory synthesis of PPVP and zircon dissolution from Egyptian zircon sand. Factors controlling parameters, such as pH values, shaking time, initial zirconium concentration, PPVP dose, nitrate ions concentration, co-ions, temperature and eluting agents, have been optimized. At 25 °C, pH 0, 20 min shaking, 0.05 mol/L zirconium ions and 0.5 mol/L nitrate ions, PPVP has an exciting preservation potential of 195 mg/g, equivalent to 390 mg/L zirconium ions. From the extraction–distribution isotherm, the practical outcomes of Langmuir’s modeling are better than the Freundlich model. With a theoretical value of 196.07 mg/g, which is more in line with the experimental results of 195 mg/g. The zirconium ions adsorption onto the PPVP composite follows the pseudo-second-order kinetics with a theoretical capacity value of 204.08 mg/g. According to thermodynamic potential, the extraction process was expected to be an exothermic, spontaneous and beneficial extraction at low temperatures. The thermodynamic parameters ΔS (−0.03 kJ/mol), ΔH (−12.22 kJ/mol) and ΔG were also considered. As the temperature grows, ∆G values increase from −2.948 kJ/mol at 298 K to −1.941 kJ/mol at 338 K. Zirconium ions may be eluted from the working loaded PPVP by 0.025M HNO3, with a 99% efficiency rate. It was found that zirconium ions revealed good separation factors towards some co-ions such as Hf4+ (28.82), Fe3+ (10.64), Ti4+ (28.82), V5+ (86.46) and U6+ (68.17). A successful alkali fusion technique with NaOH flux followed by the extraction with PPVP is used to obtain a high-purity zirconia concentrate with a zircon content of 72.77 % and a purity of 98.29%. As a result of this, the improved factors could finally be used.

Identifying the roles of Ru single atoms and nanoclusters for energy-efficient hydrogen production assisted by electrocatalytic hydrazine oxidation

With a much lower thermodynamic reaction potential, the hydrazine oxidation reaction (HzOR) can be employed as an alternative of water oxidation reaction to integrate with the cathodic hydrogen evolution reaction (HER), accomplishing an energy-efficient H2 production. The realization of this necessitates the development of the excellent bifunctional electrocatalysts for both HER and HzOR. Herein, a common Ru complex was applied to prepare a Ru/porous N-doped carbon composite (Ru/PNC) simultaneously containing abundant Ru single atoms (SAs) and ultrafine Ru nanoclusters (1.7 nm). Firstly, the new Ru/PNC catalysts containing both metal-metal as well as metal-substrate interactions display superb HER and HzOR activities in alkaline and neutral electrolytes, both greatly surpassing the sole Ru nanoparticles or Ru SAs sample. The controlled experiments and theoretical studies unravel water dissociation and H ad-desorption occurs on Ru SAs and nanoclusters, respectively, involving the proton transfer between them during the HER process, while HzOR is mainly proceeded on Ru SAs sites. Secondly, the alkaline overall hydrazine splitting with Ru/PNC only demands a voltage of 0.19 V to achieve 100 mA cm−2, demonstrating the huge energy-saving advantage compared with conventional water splitting. Additionally, the hydrogen generation can be readily operated with the hydrazine fuel cell and commercial solar cell with the appreciable H2 production rate of 32.7 and 27.1 mL cm−2 h−1, respectively.