Green hydrogen has the potential to replace fossil fuels in the energy sector and to meet environmental goals with zero-carbon emission.

Electrochemical hydrogen storage in porous activated carbons is a rapidly advancing technology, yet the composition and role of oxygen-containing surface functionalities in hydrogen storage remain underexplored. This study provides a detailed investigation of the surface and bulk properties of porous activated carbon derived from phenolic resin (aC PR) using a comprehensive multi-technique approach, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The aC PR exhibits an exceptional BET surface area of approximately 4400 m(2)/g, with a well-balanced distribution of mesopores, micropores, and ultra-micropores. Quantitative analyses reveal that aC PR is composed of 95.45 % carbon and 4.55 % oxygen, with oxygen functionalities distributed as carboxylic acid (similar to 8 %), anhydride (similar to 28 %), phenol (similar to 17 %), carbonyl and quinones (similar to 21 %), and lactones (similar to 23 %). Post-TPD treatment, the oxygen content reduces to 2.25 %, with minimal impact on the material's hydrogen storage capacity, which remains at similar to 0.60 +/- 0.05 wt% H. H-storage was measured using Proton Battery. In the proton battery, protons are generated by water splitting towards the oxygen side and are stored towards the C side in the negatively charged ac PR electrode. Ab initio molecular dynamics simulations demonstrate that both acidic and basic oxygen-containing groups have similar proton affinities, suggesting that the type of oxygen functional group plays a minimal role in hydrogen storage capacity. This work underscores the critical role of oxygen functionalities in hydrogen storage and offers new insights into the design and optimization of next-generation carbon materials for scalable hydrogen storage technologies.

Porous carbon materials with high surface area and tuneable pore distribution have been proven as suitable materials for the electrochemical storage of hydrogen, without requiring very high pressures or very low temperature being used in commercial methods for storing hydrogen. The presence of nitrogen functional groups on the surface of porous carbon materials offers the direct electrochemical bonding to hydrogen, enhance the storage performance. This report presents the study on the novel synthesis of nitrogen bonded carbon materials, using melamine and terephthalaldehyde as the nitrogen and carbon rich precursors, respectively. The sample synthesis takes place in two batches; unactivated and activated materials. One batch of samples was investigated in an unactivated form and the other with chemical activation by potassium hydroxide (KOH). Further the materials were characterised for morphology, absorption analysis, electrical conductivity, and also investigated by the physical and chemical structural analysis. Nevertheless, the gravimetric maximum reversible atomic hydrogen (H) storage was examined in a proton battery system. The first batch of samples lead to honeycomb sheet-like structure, low BET surface area, broad pore sizes with low pore volume, high nitrogen content, low electrical conductivity, while the activated sample has shown the disordered morphology, very high BET surface area, ultra micro-pores with large pore volume, rich in carbon amount, and optimal electrical conductivity. The results show the H- storage capacity of the unactivated samples increased monotonically with an increase of the melamine (nitrogen) proportion. However, for the activated samples, H storage capacity decreased with an increase of melamine as a precursor. The highest gravimetric reversible H storage capacities of 0.44 wt% were found for the unactivated sample and the H storage of 0.62 wt% for the activated materials. At the end, the future prospects of carbon-nitrogen materials as electrode for H storage are discussed. However, the atomic storage in such materials has been less explored in literature. Nevertheless, the H storage phenomenon in proton battery can surpass many commercially available hydrogen storage methods, which often require either very high pressure or extremely low temperature.

The various form of nitrogen bonded carbon materials has become an apparent choice as electrodes to enhance the electrochemical performance of energy storage devices. In particular, C–N–H bonds, or direct N–H bonds participates in pseudo-capacitance, hence, enhance the overall capacitance of the storage system. However, the position of nitrogen in lattice and its type of bonding with carbon atoms can influence the electrochemical reactions. Thus, this review article focuses on nitrogen functionalities attached carbon materials refer as nitrogenated carbon materials and its associated nitrogen configurations present in it. Also, their synthesis route in order to achieve such materials has been discussed. Nevertheless, evident enhancement in electrochemical performance via pseudocapacitive reaction of such N contained materials has been presented. A chronological study of nitrogen bonded carbon materials for potential application has been reviewed and conclude the necessity of these materials for electrochemical storage for energy applications.

Abstract The very large global demand for energy storage as inherently-variable renewable-energy sources meet an increasing proportion of total electricity demand will be difficult to meet solely with existing technologies. Hence additional storage technologies that are safe and based on abundant primary resources are likely to come into play to facilitate the transition to zero net emissions at the global level. One such promising technology is the ‘proton battery’, which in its most general form is a rechargeable battery based on proton transfer and reversible electrochemical hydrogen storage. In the present review, a general definition of a proton battery is first proposed, since the term has been used broadly and somewhat inconsistently to date. The literature over the past thirty years on this technology is then critically reviewed, covering both proton batteries that meet the definition proposed in this paper as well as those that are merely self-identified. To the extent possible through published information, the performances of this range of cells are compared in terms of key parameters such as electrical energy stored per unit mass, cyclability, self-discharge and scale reached. The proton battery design developed by our group at RMIT is described in more detail, both theoretically and in terms of experimentally-measured performance, as an exemplar of a system that has already demonstrated a competitive storage capacity at a significant scale. In conclusion, potential future applications for proton batteries, and some directions for the research and development necessary to enable this potential to be realised, are proposed.

Nowadays, the usage of fossil fuel has been raised as a non-sustainable resource, account for the main contributor to global warming (CO2 emission) and environmental pollutions. In this regard, the hydrogen production through polymer electrolyte membrane (PEM) water electrolysis is an industrially important approach to resolving the above energy issues. Precious metals are the top metal-catalysts that can offer to generate hydrogen efficiently and earth-abundant nonprecious metal catalyst has large overpotential issues because of a low electro-activity. Therefore, the production of pressurized hydrogen through polymer exchange membrane (PEM) water electrolysis without the usage of the external compressor is an industrially important approach to maximize energy efficiency. Because hydrogen is believed to be a clean energy carrier to store the excess renewable energy to resolve its intermittent issues. Although over 96% of the current hydrogen produced is via the reformation of natural gas and the remaining 4% produced from water electrolysis and it is the “green” approach to produce hydrogen without CO2 emission. In this report, we demonstrated the operation of a new water electrolysis cell at high water support pressure with the assistance of a hydrophobic gas diffusion layer (H-GDL) and demonstrated a high-pressure PEM water electrolysis experiment with the assistance of a newly structured water electrolysis cell (Fig.1a). The membrane electrode assemblies (MEAs) was prepared using H-GDL, membrane, Pt-C//IrO2 and the electrolysis experiment was performed at different temperature and water support pressure (ΔP = 0.05-0.4 MPa). The current density obtained at 1.6 V were 117, 188, 262 mA cm-2 at 25, 60, and 80oC (Fig.1b), respectively, and the generated gas evolution rates (hydrogen and oxygen) were consistent with theoretical value with efficiencies up to 87%. It was found that increasing water pressure is beneficial to the electrode kinetics and mass-transportation due to an increase in water transport to the electrode surface and efficient gas separation. The benefits of using GDL is, therefore, lying on two points. Firstly, high pressure can be applied to the water, which allows the operation of the cell at a temperature higher than 100℃, while maintaining the water in the liquid phase and secondly the high-pressure operation using H-GDL is the production of pressurized hydrogen gas without the use of an external compressor. As advantages, in the future, it can be directly used to fuel cell and that can be stored in a hydrogen tank without further purification process. Figure 1

A novel idea of using carbon foam (CF) is introduced to enhance the electrochemical performance of a slurry electrode system in a proton flow reactor system. Steam -activated and acid -washed Norit from peat is used as active charge carrier particles to prepare 15 wt% carbon slurry to be used in this study. The slurry flow rates in the experimental electrochemical system can be varied from 0 to 200 ml min -1 , while using two channel widths of 1.6 cm and 2 cm to facilitate the slurry flow. Two sets of CFs with 10 pores per inch (PPI) and 5 PPI are used to understand the effect of introducing CFs with different pore sizes on the performance of slurry electrode. Slurry is charged slurry up to 100 C under constant application of 10 mA and 30 mA. After adding CF, the results show a significant drop in charging potential to generate both levels of current of 25% after using 5 PPI and 41% with 10 PPI. Furthermore, using the narrow channel flow of 1.6 cm and increasing the slurry flow rate from 100 ml min -1 to 150 ml min -1 lower the charging potential considerably by 19% and 21% (compared to base slurry) for 5 PPI and 10 PPI CF, respectively. Application of CF further enables the system to attain higher discharging time during the discharge cycle, and a maximum of 336% and 115% discharging capacity improvement is observed with 10 PPI and 5 PPI CF, respectively.

Redox flow batteries (RFBs) are one of the hopes for grid energy storage applications. Among the various RFBs, the vanadium redox flow battery (VRFB) has the specific advantage of deploying the same element, i.e., vanadium in different oxidation states in both negolyte and posolyte. However, its major unmet concern is the poor charge retention during cycling, attributed to cross-contamination of vanadium across the separator. Perfluorosulfonic acid-based cation exchange membranes (CEMs) are the preferred separators for VRFB. Nevertheless, for the negatively charged matrix of CEMs, redox-active vanadium species are the counterions and easily diffuse through, leading to capacity decay. To counter the crossover, the benefit of Donnan exclusion has been considered. For this reason, anion exchange membranes (AEMs) are encouraged for VRFB. The positive charge on AEMs can effectively exclude the vanadium ions, but AEMs have the limitation of low ionic conductivity and questionable chemical stability in a highly oxidative flow battery environment. In recent years, the membrane research community has adopted different strategies to counter the cross-contamination of the vanadium ions between the electrodes and boost the overall performance of the battery. In this review, we will focus on the various approaches developed for the advancement of VRFB membranes.

The world is moving rapidly to embrace renewable energy sources. One energy carrier, hydrogen, is a growing player in this field. This study was motivated by a desire to find alternative hydrogen storage mechanisms using processes that are cost effective with low environmental impact and good energy storage efficiency. This paper presents initial research findings on the novel approach of employing the patented RMIT Proton Battery to store atomic hydrogen in a multilayer graphene electrode using an acid electrolyte. This is a very different approach to conventional hydrogen energy storage systems. The paper reveals that one supplier's product achieves a 0.35 wt% reversible hydrogen storage in a multilayer graphene material with 0.35 nm layer separation and a specific surface area of 720 m(2)/g. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Vanadium-based alloys are potential materials for hydrogen storage applications in Remote Area Power Supply (RAPS) and Movable Power Supply (MPS). In this study, V80Ti8Cr12 alloys are tailor-made to meet the RAPS and MPS working conditions (293-323 K and 0.2-2 MPa). The effects of pulverization methods and particle sizes on the alloy's hydrogen storage properties have been systematically investigated. In addition, a novel PressureComposition-Isotherm approach is employed for the first time to accurately evaluate the hydrogen storage capacities. The reduction of particle size enhances the absorption kinetics due to the increased surface area. However, mechanical pulverization causes lattice distortion that decreases the hydrogen absorption capacity and desorption rate. In contrast, hydrogen embrittlement can effectively pulverize the alloys without generating lattice distortion. The results reveal that 5 mm sample, which is simply subjected to hydrogen embrittlement, achieves the largest usable hydrogen storage capacity up to 2.1 wt% and the fastest hydrogen desorption rate of similar to 4 sccm/g that is nine times quicker than required for RAPS and MPS applications. After 500 cycles, the 5 mm alloy retains 90 % of its capacity, demonstrating excellent durability. Hence, 5 mm hydrogen-embrittled V80Ti8Cr12 alloy is an ideal hydrogen storage material in RAPS and MPS systems.

The supply of species gases and removal of liquid water in a PEM fuel cell are performed through gas flow channels. Therefore, optimising the flow channel configurations is critical for maximising performance of fuel cells. In this paper, the ANSYS PEM Fuel Cell Module is used to simulate a PEM fuel cell with an active area of 100 cm2 and four different flow channel configurations: single-channel serpentine, two-channel serpentine, three-channel serpentine, and parallel channel with headers under two set of different operating conditions. Under both sets of operating conditions, the simulation results indicated that 3-channel serpentine configuration has the best performance due to uniform distribution of species gases over the catalyst layer. It was concluded from the simulation results that the pressure-drop along the 3-channel serpentine configuration is less compared to other serpentine channel configurations, which will require less power for the blowing in of the species gases. The results obtained from simulation under more optimal operating conditions (set 2) used by Hwang's URFC, predicted increase in the performance of all the four channel configurations compared to the set 1 operating conditions due to higher cell temperature and stichometry of inlet gases. Under set 2 operating conditions, the values of pressure drop across all the channel configurations have increased substantially due to higher flow rates of inlet gases.

The charge storage and distribution in a porous conductive carbon material, in the presence and absence of electrolyte, are studied using the Poisson-Nernst-Planck equations for the first time in the literature. By solving the Laplace equation, it is found that the charge distribution inside the pores is negligible in the absence of the electrolyte. In the presence of cations and anions of the electrolyte inside the pores, the charge distribution on the pore surfaces and ionic concentration gradients in the electrolyte are numerically evaluated by solving the Poisson-Nernst-Planck equations. The modelling results predict the classic electric double layer structure for meso- and larger pores. For smaller nano-level pores, however, the equations predict a structural shift from a classic electric double layer towards a near-uniform ion storage inside the pores, that is, a concentration of counter ions within pores. The accuracy level of the results is then analysed considering modified Poisson-Nernst-Planck equations, relative permittivity variations of the electrolyte, and the validity of the continuum assumption. The modelling predictions are experimentally tested by measuring the charge storage under different electrolyte concentrations in two activated carbon samples with different pore structure characteristics. (c) 2021 Elsevier Ltd. All rights reserved.

Electrochemical storage of neutralised protons in porous carbon materials such as activated carbons and multi-layer graphene is becoming possible using novel technologies such as the proton battery and proton flow reactor. This set-up is a promising option for electrical energy storage at various scales, and possibly for exporting a zero-emission hydrogen-based fuel. This paper focusses on understanding and identifying the contributions to hydrogen storage in activated carbon from phenolic resin (aC PR) from processes such as electric double layer capacitance, electrosorption, cationic concentration by intercalation in ultramicropores, and reversible faradaic (redox) reactions between hydronium, and negatively-charged carbon surfaces inside pores with and without intermediary oxygen groups. A combination of XPS, Raman, and infrared spectroscopy is employed to identify the forms of C⋯H reactions involved, together with temperature programmed desorption, cyclic voltammetry and galvanostatic charging and discharging. Experimental evidence for the formation of C⋯H bonding in aC PR is presented, which promises to be sufficient for use of this and similar carbon materials as a solid-state hydrogen storage material with competitive energy density.

The present paper reports on experiments to improve theoretical understanding of the basic processes underlying the operation of a 'proton battery' with activated carbon as a hydrogen storage electrode. Design changes to enhance energy storage capacity and power output have been identified and investigated experimentally. Key changes made were heating of the overall cell to 70 degrees C, and replacement of the oxygen-side gas diffusion layer with a much thinner titanium-fibre sheet. A very substantial increase in reversible hydrogen storage capacity to 2.23 wt%H (598 mAh g(-1), 882 J g(-1)) was achieved. This capacity is nearly three times that of the earlier design, and more than double the highest electrochemical hydrogen storage using an acidic electrolyte previously reported. It is hypothesised that the main cause of the major gain in storage is an enhanced water formation reaction on the O-side through reduced flooding. In addition, an alternative mode of discharging a proton battery has been discovered that allows direct generation of hydrogen gas from the hydrogenated carbon material, by a 'hydrogen-pump' type of reaction. The hydrogen gas evolved is high purity, and thus may ultimately create opportunities for use of this storage technology in hydrogen supply chains for fuel cell vehicles.

Electrochemical hydrogen storage in porous carbon materials is emerging as a cost-effective hydrogen storage and transport technology with competitive power and energy densities. The merits of electrochemical hydrogen storage using porous conductive carbon-based electrodes are reviewed. The employment of acidic electrolytes in such storage systems is compared with alkaline electrolytes. The recent innovations of a proton battery for smaller-scale electricity storage, and a proton flow reactor system for larger (grid)-scale storage and bulk export of hydrogen produced from renewable energy, are briefly described. It is argued that such systems, along with variants proposed by others, all of which rely on electrochemical hydrogen storage in porous carbons, can contribute to the search for energy storage technologies essential for the transition to a zero-emission global economy.

Polymer Exchange Membrane Fuel Cell (PEMFC) is emerging as a promising candidate for the future power source. Research works have been focused on small PEMFCs while its scalability and performance of large cells remain elusive. This paper presents a numerical investigation on the practicality of expanding a small PEMFC to a large one and a parametric study on the impact of relative humidity (RH) on the operational performance of the large cell. Numerical predictions are firstly validated against our in-house experimental measurements where the predicted polarization (V-I) curve is in good agreement with the measurements. Numerical results confirm that water accumulation/flooding exhibits different characteristics at different regions, namely the activation, ohmic-loss, and concentration loss regions, and poses significant impacts on the current density production. Numerical results also show the small cell is more susceptible to water flooding in comparison to the large cell under similar operational conditions. Suffering from excessive liquid water, the performance of the small cell is not as good as the large one in the concentration loss region, where a significant increase of current density production is observed. Parametric study on the effect of the humidified reactants on cell performance has been also performed. The increase of RH generally shows an increasing effect on the performance of the cell, while the limitation is found at high RHs (60% and 80%) and low voltage (0.3V) due to the hydration of the membrane and the blockage of reactant delivery.

Electrochemical energy storage using slurry flow electrodes is now recognised for potentially widespread applications in energy storage and power supply. This study provides a comprehensive review of capacitive charge storage techniques using carbon-based slurry electrodes. Carbon particle properties and their effects on the performance of slurry flow electrodes are thoroughly reviewed. A detailed analysis of electrochemical properties of slurry flow electrodes is provided, including their dependence on the concentration ratio of electrolyte to carbon, flow behaviour, and design flow channel configuration. This paper also identifies key challenges and research gaps to be addressed by future research studies for improving the performance of carbon-based slurry flow electrodes on their path to further commercialisation.

Fabrication and testing of Proton Exchange Membrane (PEM) fuel cells to improve performance is an expensive and time-consuming process. This paper presents a novel procedure for using computer simulation - namely the ANSYS PEM Fuel Cell Module - to identify key performance limiting factors in fuel cell mode of a PEM Unitised Regenerative Fuel cell (URFC) fabricated at RMIT by comparing its performance with a higher performing URFC reported in the literature. The diagnostic analysis is performed in two steps: firstly, changing operating conditions to ensure both cells are compared based on the same conditions; secondly identifying differences in cell properties, specifically catalyst exchange current densities and membrane conductivity. The simulation results show that applying the more optimal operating conditions of the higher performing cell doubled the maximum power of the RMIT cell (from 0.163 W/cm(2) to 0.327 W/cm(2)). To overcome the remaining performance deficit in the ohmic polarization region, the value of the protonic conduction coefficient in the modelled RMIT cell had to be increased. Overall the study indicates that computer simulation modelling, in conjunction with carefully focussed experiments, can be a very useful tool in diagnosing fuel-cell performance problems. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Matching simulated and experimental polarization curves is an essential step in the modelling of polymer electrolyte membrane (PEM) fuel cells, but the numerical values of many input parameters like exchange current densities, charge transfer coefficients, protonic conduction coefficient and water removal coefficient are hard to be found experimentally. In this paper, the influence of these input parameters on the performance of PEM fuel cells has been investigated using the ANSYS PEM Fuel Cell Module. The simulation results show how the exchange current densities and charge transfer coefficients influence the activation losses; membrane resistance and contact resistance between the different components of a fuel cell contribute to the ohmic losses; and the coefficient of liquid water removal affects the concentration losses. A systematic procedure to match a simulated polarization curve with an experimental curve is presented and illustrated by application to an experimental PEM fuel cell with 5 cm(2) active area. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.