Hydrogen generation from catalytic hydrolysis of sodium borohydride by a Cu and Mo promoted Co catalyst

Highly Active and Robust Catalyst: Co2B-Fe2B Heterostructural Nanosheets with Abundant Defects for Hydrogen Production

A high-performance and reusable nonnoble metal catalyst for catalyzing sodium borohydride (NaBH4) hydrolysis to generate H2 is heralded as a nuclear material for the fast-growing hydrogen economy. Boron vacancy serves as a flexible defect site that can effectively regulate the catalytic hydrolysis performance. Herein, we construct a uniformly dispersed and boron vacancy-rich nonnoble metal Co2B-Fe2B catalyst via the hard template method. The optimized Co2B-Fe2B exhibits superior performance toward NaBH4 hydrolysis, with a high hydrogen generation rate (5315.8 mL min-1 gcatalyst-1), relatively low activation energy (35.4 kJ mol-1), and remarkable cycling stability, outperforming the majority of reported catalysts. Studies have shown that electron transfer from Fe2B to Co2B, as well as abundant boron defects, can effectively modulate the charge carrier concentration of Co2B-Fe2B catalysts. Density functional theory calculations confirm that the outer electron cloud density of Co2B is higher than that of Fe2B, among which Co2B with high electron cloud density can selectively adsorb BH4- ions, while the electron-deficient Fe2B is favorable for capturing H2O molecules, therefore synergistically promoting the catalytic NaBH4 hydrolysis to produce H2.

CuNi Alloy NPs Anchored on Electrospun PVDF-HFP NFs Catalyst for H2 Production from Sodium Borohydride

Non-noble Cu_xNi_1-x (x = 0, 0.1, 0,2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1) alloy nanoparticles supported on poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP) nanofibers (NFs) are successfully fabricated. The fabrication process is executed through an electrospinning technique and in situ reduction in Cu²⁺ and Ni²⁺ salts. The as-synthesized catalysts are characterized using standard physiochemical techniques. They demonstrate the formation of bimetallic NiCu alloy supported on PVDF-HFP. The introduced bimetals show better catalytic activity for sodium borohydride (SBH) hydrolysis to produce H₂, as compared to monometallic counterparts. The Cu_0.7 Ni_0.3/PVDF-HFP catalyst possesses the best catalytic performance in SBH hydrolysis as compared to the others bimetallic formulations. The kinetics studies indicate that the reaction is zero order and first order with respect to SBH concentration and catalyst amount, respectively. Furthermore, low activation energy (Ea = 27.81 kJ/mol) for the hydrolysis process of SBH solution is obtained. The excellent catalytic activity is regarded as the synergistic effects between Ni and Cu resulting from geometric effects over electronic effects and uniform distribution of bimetallic NPs. Furthermore, the catalyst displays a satisfying stability for five cycles for SBH hydrolysis. The activity has retained 93% from the initial activity. The introduced catalyst has broad prospects for commercial applications because of easy fabrication and lability.

Rehydrogenation of Sodium Borates to Close the NaBH4-H2 Cycle: A Review

In 2007, the US Department of Energy recommended a no-go on NaBH4 hydrolysis for onboard applications; however, the concept of a NaBH4-H2-PEMFC system has the potential to become a primary source for on-demand power supply. Despite the many efforts to study this technology, most of the published papers focus on catalytic performance. Nevertheless, the development of a practical reaction system to close the NaBH4-H2 cycle remains a critical issue. Therefore, this work provides an overview of the research progress on the solutions for the by-product rehydrogenation leading to the regeneration of NaBH4 with economic potential. It is the first to compare and analyze the main types of processes to regenerate NaBH4: thermo-, mechano-, and electrochemical. Moreover, it considers the report by Demirci et al. on the main by-product of sodium borohydride hydrolysis. The published literature already reported efficient NaBH4 regeneration; however, the processes still need more improvements. Moreover, it is noteworthy that a transition to clean methods, through the years, was observed.

Recent developments of nanocatalyzed liquid-phase hydrogen generation

Hydrogen is the most effective and sustainable carrier of clean energy, and liquid-phase hydrogen storage materials with high hydrogen content, reversibility and good dehydrogenation kinetics are promising in view of "hydrogen economy". Efficient, low-cost, safe and selective hydrogen generation from chemical storage materials remains challenging, however. In this Review article, an overview of the recent achievements is provided, addressing the topic of nanocatalysis of hydrogen production from liquid-phase hydrogen storage materials including metal-boron hydrides, borane-nitrogen compounds, and liquid organic hydrides. The state-of-the-art catalysts range from high-performance nanocatalysts based on noble and non-noble metal nanoparticles (NPs) to emerging single-atom catalysts. Key aspects that are discussed include insights into the dehydrogenation mechanisms, regenerations from the spent liquid chemical hydrides, and tandem reactions using the in situ generated hydrogen. Finally, challenges, perspectives, and research directions for this area are envisaged.