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Upon alloy Pt with tin significant improvement in fuel cell performance is achieved.

Platinum (Pt) is the most common catalyst in Polymer Electrolyte Membrane Fuel Cells due to its ability to effectively promote the oxidation of hydrogen and reduction of oxygen. However, as a noble metal, the use of Pt should be minimized. Alloying Pt with low-cost transition metals is an effective strategy to improve catalytic activity and reduce Pt use. In this context, we report on a one-step synthesis of a Platinum/Copper (PtCu) catalyst, which can be used at both the anode and the cathode of a fuel cell. Catalysts with various Cu to Pt ratios were synthesised and in particular the PtCu catalyst at a Cu to Pt ratio of 0.5 demonstrated a high activity for hydrogen oxidation and oxygen reduction, i.e. 2.4 times superior to Pt alone. This enhanced catalytic activity was confirmed in a self-breathing PEMFC with a power output of 45.16 mW cm−2, which corresponds to a 1.4-fold increase compared to Pt alone. This is a significant improvement because 40% more power was obtained with 22% less Pt. Graphical Abstract

Defect sites (comprising Ti3+ and NBOHC) and oxygen adsorbed on a Pt surface (PtOads) boost catalytic oxygen activation on a Pt/TiO2–SiO2 catalyst.

Grignard reagents can provide a simple path to generate, through their thermal decomposition, magnesium (Mg) and/or its hydride (MgH2). However, existing compounds lack the ability to lead to “adequate” MgH2 structures to enable effective hydrogen storage. Herein, we report on the possibility to tune Grignard reagent's chemical structure, i.e. number of β-hydrogen, and the activation energy for their thermal decomposition to lead to Mg/MgH2. For example, di-tert-butylmagnesium with nine β-hydrogen was able to decompose at a very low temperature of 167 °C to generate MgH2/Mg, which is 100 °C lower than the temperature required to generate MgH2 from di-n-butylmagnesium, i.e. the only compound known to date. More remarkably, the MgH2 synthesized from the di-tert-butylmagnesium precursor was able to release hydrogen from 100 °C. These promising hydrogen storage properties are credited to the formation of the metastable γ-MgH2 phase, which is believed to result from the structural defects generated upon the thermal decomposition of di-tert-butylmagnesium.

Borohydride (LiBH4, NaBH4 and KBH4) nanoparticles were successfully synthesized by a modified ternary anti-precipitation method. A co-solvent was introduced to facilitate the formation of a microemulsion and modify the metastable zone to favour the precipitation of borohydride particles. In this process, the stabilising surfactant's carbon chain length was found to provide an additional mean to further tune particle size due to the resulting steric hindrance. The method reported here finally provides an effective and simple mean to prepare nanosized borohydride particles for hydrogen storage purposes, while minimising the amount of stabilising surfactant that can contaminate the hydrogen release.

Requiring high temperature for hydrogen storage is the main feature impeding practical application of light metal hydrides. Herein, to lift the restrictions associated with traditional electric heating, light is used as an alternative energy input, and a light-mediated catalytic strategy coupling photothermal and catalytic effects is proposed. With NaAlH

Many studies have demonstrated the feasibility of utilizing light-mediated electronic perturbations to regulate or promote the thermal catalytic conversion of CO2 to methanol. However, such studies...

The investigation of nanoscale complex hydrides for hydrogen storage application has gained the spotlight in the past decade. Herein, the thermodynamic behavior of complex borohydrides confined in ...

Heteropoly acids have attracted great attention as potential solid-state proton-conducting materials owing to their high proton conductivity of 10–2 S cm−1 at room temperature. However, the proton conductivity can be significantly reduced under operating conditions due to the leaching of water molecules out of the acid Keggin structure. In the present study, silicotungstic acid (SiWA) was encapsulated in the mesoporous structure of the chromium (III) terephthalate metal–organic framework (MIL-101) in an attempt to prevent water loss and preserve proton conductivity. This hybrid material was then shaped into a membrane with the aid of polyvinyl alcohol (PVA). This approach of SiWA encapsulation with PVA addition to form a membrane proved to be successful as the proton conductivity of the resulting membranes was found to be of 2.4 × 10–2 S cm−1 at 25 °C and 25% RH. Under low levels of hydration, when the membrane was dried at 80 °C, the proton conductivity still remained high (1.9 × 10–2 S cm−1). This improved proton conductivity is believed to be the result of the continuous channels for facile proton transport created through the immobilisation of the heteropoly acid within the MIL-101 framework.

The core-shell approach has surfaced as an attractive strategy to make complex hydrides reversible for hydrogen storage; however, no synthetic method exists for taking advantage of this approach. Here, a detailed investigation was undertaken to effectively design freestanding core-shell NaBH

Although solar irradiation has demonstrated beneficial synergy for catalytic CO2 hydrogenation, it has long been debated as to whether the observed photo-assisted catalytic enhancement has a photo-activation component or is driven solely by the heating effect. Here, we confirm that surface adsorbates play a critical role in photo-assisted CO2 activation. We isolate the rate-determining intermediate species in the photo-assisted Sabatier reaction by in situ isotopic spectroscopy. Specifically, we reveal that photo-activation of the formate adsorbate (HCO2*) offers an eightfold photo-enhancement on NiOx/La2O3@TiO2. Concurrently, the active La2O3@TiO2 support facilitates the adsorption of CO2, which may contribute to the sustained HCO2* formation and conversion. The findings are crucial as they provide surface intermediary insights in the design of catalysts for photo-assisted CO2 conversion. Ultimately, the understanding may unlock the solar-driven hydrogenation catalytic pathway for other reactions involving HCO2* such as the synthesis of methanol. Although the light-promoted Sabatier reaction has great potential for CO2 remediation strategies, its mechanism is not fully understood. Now, a steady-state isotopic kinetic analysis coupled with infrared spectroscopy reveals important aspects of this hydrogenation process over a NiOx/La2O3@TiO2 composite catalyst.

NaBH4 is a promising material for hydrogen storage because of its high hydrogen density (10.8 mass %). However, the sluggish hydrogen kinetics and poor thermodynamics of the dehydrogenation process...

The ionic conduction in the metal borohydrides is often linked to the energy barriers of BH4− reorientation and cation diffusion. However, the ionic conduction is a complex phenomenon, and limited reports are available to establish straightforward correlations with experimental trends in alkali metal borohydrides. This communication reported the correlations between ionic conductivity and cationic size in complex borohydrides. The ionic conductivities of LiBH4, NaBH4, and KBH4 were found to decrease monotonically with increasing cationic radius. This evidences that borohydrides follow trends observed for other ionic conductors and provide further ground toward designing better borohydride-based electrolytes.

Although photoexcitation has been employed to unlock the low-temperature equilibrium regimes of thermal catalysis, mechanism underlining potential interplay between electron excitations and surface chemical processes remains elusive. Here, we report an associative zinc oxide band-gap excitation and copper plasmonic excitation that can cooperatively promote methanol-production at the copper-zinc oxide interfacial perimeter of copper/zinc oxide/alumina (CZA) catalyst. Conversely, selective excitation of individual components only leads to the promotion of carbon monoxide production. Accompanied by the variation in surface copper oxidation state and local electronic structure of zinc, electrons originating from the zinc oxide excitation and copper plasmonic excitation serve to activate surface adsorbates, catalysing key elementary processes (namely formate conversion and hydrogen molecule activation), thus providing one explanation for the observed photothermal activity. These observations give valuable insights into the key elementary processes occurring on the surface of the CZA catalyst under light-heat dual activation., CO2 to methanol synthesis is a promising approach for renewable fuel production. Here, the authors show that UV and visible light dual activation promotes photothermal methanol production at the copper-zinc oxide interfacial perimeter by accelerating formate conversion and hydrogen molecule activation.

Sodium borohydride (NaBH4) is a promising hydrogen storage material due to its potential for reversible hydrogen storage with high hydrogen capacity (10.8 mass%). However, the temperature at which hydrogen can be released from NaBH4 is too high (> 500 °C) for practical use and the reversible release of hydrogen is only feasible under severe conditions of temperature and pressure. Nanosizing is an effective strategy to improve the hydrogen properties of NaBH4. In this context, control over the particle size of NaBH4 has become important. Herein, we report on a solvent evaporation method for the synthesis of isolated NaBH4 nanoparticles with varying mean particle sizes and morphologies. In particular, the effects of surfactants’ carbon chain lengths, their steric hindrance and functional groups in facilitating the stabilisation of NaBH4 nanoparticles of various sizes and shapes were investigated. Longer linear carbon chains bearing hard type functional groups were found to favour the growth of smaller NaBH4 nanoparticles.

Polymer Electrolyte Membrane Fuel Cells (PEMFC) are often viewed as enablers of decarbonised energy systems since they transform hydrogen directly into electricity with water as the main by-product. The attraction for fuel cells is also in their versatility because they can be implemented across a wide range of applications from microelectronics to large scale power generation. Herein, we review recent progress on the design and fabrication of PEMFC with a special focus on their air-breathing planar configuration as this extends the possibility of PEMFC to thin and flexible designs. To date, the deployment of planar PEMFC highly depends upon scientific progress and technological solutions for cost reduction and long-term durability including the development of better proton conducting membranes and platinum-free catalysts to drive the oxygen reduction and hydrogen oxidation reactions efficiently. Long term durability is another challenge that can be addressed through the advancement of inexpensive and lightweight current collectors and highly efficient gas diffusion electrodes for better distribution of the reactants while maintaining an optimum hydration of the proton conducting membrane. Innovative fabrication methods for the various components of planar PEMFC as well as effective stack design and assembly are also critical for efficiency maximization, reproducibility and overall cost reduction.

The design and development of highly efficient and stable oxygen evolution reaction (OER) electrocatalysts in acid media are important for various renewable technologies. Herein, an advanced Co3O4 electrocatalyst supported on a mesoporous hydrophobic carbon paper (Co/29BC) is formed via a simple one‐step thermal decomposition of cobalt nitrate. Through this novel approach, the amorphous carbon layer resulting from the thermal decomposition of carbon‐containing species in the mesoporous layer provides enhanced electronic conduction and protection against corrosion to the Co3O4 nanoparticles. Equally important, the OER performance is found to be correlated with the morphology and surface composition of Co3O4. With optimized Co3+ active sites and oxygen vacancies at the metal oxide surface, the Co3O4 catalyst shows superior OER performance and durability in a proton exchange membrane (PEM) water electrolyzer, with a small overpotential (350 mV) at a constant current density of 10 mA cm−1 for over 50 h. Accordingly, this work provides new insights toward the design of high‐performance and highly stable OER electrocatalysts in corrosive acidic environments.

This work reports on the synthesis of iron-platinum on Vulcan carbon (FePt/VC) as an effective catalyst for the electrooxidation of molecular hydrogen at the anode, and electroreduction of molecular oxygen at the cathode of a proton exchange membrane fuel cell. The catalyst was synthesized by using the simple polyol route and characterized by XRD and HRTEM along with EDS. The catalyst demonstrated superior electrocatalytic activity for the oxygen reduction reaction and the oxidation of hydrogen with a 2.4- and 1.2-fold increase compared to platinum on Vulcan carbon (Pt/VC), respectively. Successful application of FePt/VC catalyst in a self-breathing fuel cell also showed a 1.7-fold increase in maximum power density compared to Pt/VC. Further analysis by accelerated stress test demonstrated the superior stability of FePt on the VC substrate with a 4% performance degradation after 60,000 cycles. In comparison, a degradation of 6% after 10,000 cycles has been reported for Pt/Ketjenblack.

To date, hydrogen generation and storage are two separated processes. We report on a new concept where photocatalytically generated hydrogen is simultaneously stored in-situ within the material photo-generating hydrogen. To this aim, we successfully synthesised a “forest” of vertically aligned TiO2 nanotubes decorated with Pd nanoparticles acting as the hydrogen store. Upon illumination of TiO2, hydrogen was effectively generated and full storage of hydrogen within the Pd nanostructures was achieved within 100 min. This result demonstrates new avenues on the possibility of designing hybrid nanostructures for the effective use of hydrogen as an energy vector.

Tailoring oxide functionalities via defect engineering is an effective approach in many advanced materials. Here we report that introducing defect sites in SiO2 via sequential hydrogenation and UV light pre-treatment steps can invoke synergism for oxygen activation and organic dehydrogenation under ambient conditions in the absence of light. The hydrogenation step is proposed to break Si O Si bonds to give an E′δ center – silanol pair. UV light pre-treatment then serves to dehydroxylate the silanol group to give a non-bridging oxygen hole centers (NBOHC). The two defect sites work in harmony to activate oxygen and in turn oxidize formic acid. First-principles calculations indicated that UV light pre-treatment lowered the energy barrier for oxygen activation and formic acid decomposition on the defect sites. Re-illuminating the used SiO2 led to partial recovery of the defect sites and hence oxidation performance. The study demonstrates the capacity for generating synergistic defects in simple metal oxides as an effective way to enhance performance for oxidation processes.

Titanium-iron (TiFe) is known to be a low-cost alloy that can be reactivated to nearly full hydrogen storage capacity after oxidation. However, this reactivation requires multiple heat treatments at high temperatures under vacuum even upon partial substitution of Fe with a small amount of manganese to form TiFe0.85Mn0.15. This process is cumbersome in the context of practical applications, and better strategies for the facile activation of TiFe are required. Herein, we report on an improvement in the reactivation strategy of TiFe0.85Mn0.15 by using a single heat treatment process after air oxidation of the alloy. After full oxidation of the material under air for 2 h, reactivation was achieved in a single step by heating the alloy to 300 °C under hydrogen pressure. During that process, the reduction of Fe was believed to lead to new reactive paths at the surface of the alloy facilitating the permeation of hydrogen. As a result, full cycling capability of the material was quickly re-gained, and the hydrogen capacity loss was of only 0.1 mass%.

AlH 3 (alane) is considered as an ideal one-off compact hydrogen storage material thanks to its high storage capacity and moderate decomposition temperature. However, application has been hindered by the lack of direct hydrogen reversibility, i.e. regeneration of AlH 3 directly from the reaction of spent Al with hydrogen under mild conditions. Herein, we investigated the effect of nanoconfinement on the properties of AlH 3 and the potential of this approach toward the direct release and uptake of hydrogen by nanosized Al. AlH 3 was confined within the mesopores of a high surface area graphite (HSAG). The decomposition of the nanoconfined AlH 3 was detected 50 °C lower than the bulk, showing some effect of nanoconfinement on the overall temperature for hydrogen release. Some hydrogen uptake was also observed at 150 °C and 60 bar hydrogen pressure, and this indicates that reversible release of hydrogen with alane under moderate conditions of pressure and temperature may be possible.

Hydrogen has been long known to provide a solution toward clean energy systems. With this notion, many efforts have been made to find new ways of storing hydrogen. As a result, decades of studies has led to a wide range of hydrides that can store hydrogen in a solid form. Applications of these solid-state hydrides are well-suited to stationary applications. However, the main challenge arises in making the selection of the Metal Hydrides (MH) that are best suited to meet application requirements. Herein, we discuss the current state-of-art in controlling the properties of room temperature (RT) hydrides suitable for stationary application and their long term behavior in addition to initial activation, their limitations and emerging trends to design better storage materials. The hydrogen storage properties and synthesis methods to alter the properties of these MH are discussed including the emerging approach of high-entropy alloys. In addition, the integration of intermetallic hydrides in vessels, their operation with fuel cells and their use as thermal storage is reviewed.