Recent Advances of Catalysis in the Hydrogenation and Dehydrogenation of N-Heterocycles for Hydrogen Storage

Abstract

Lack of efficient hydrogen storage method is one of the technical bottlenecks for the implementation of hydrogen energy. Liquid organic hydrogen carriers (LOHCs), especially Nheterocycles, have been considered as potential candidates for both on-board and off-board hydrogen storage owing to their low cost, high gravimetric hydrogen storage capacity, reversibility, and compatibility with the existing infrastructures with minimal modification. LOHCs however encounter severe kinetic barriers in the hydrogen uptake and release processes, and thus efficient catalysts are critically needed. Much attention has been given to the design and development of catalysts for the reversible hydrogenation and dehydrogenation of N-heterocycles. In this Mini-Review Article, we summarize recent activities in advancing those compounds for hydrogen storage through thermo-, photo-, and electrocatalysis, aiming to provide a guidance for rational catalyst design. At the end of the Mini-Review Article, challenges and future research directions of the catalyst design in the LOHCs field are discussed.

Toward a Hydrogen Economy: Development of Heterogeneous Catalysts for Chemical Hydrogen Storage and Release Reactions

“…In the area of chemical hydrogen storage and release, many outstanding reviews, perspectives, and accounts on heterogeneous and homogeneous catalytic systems have sprung up, ,,− most of which focus on one of the chemical H 2 carriers [formic acid (including formate salts), − N -heterocycles, ,,− (aromatic) hydrocarbons, ,− ammonia, , ammonia–borane, or dimethyl ether] or on the individual hydrogen production/​release reactions. − Notably, in a large proportion of the previous reports, only one individual reaction, either H 2 storage or H 2 release, is involved or discussed rather than combining those individual reactions to demonstrate the overall concept of chemical H 2 batteries; even the research works are very often entitled to contain the topic of “H 2 storage and release”. Those examples are not considered in this Review.…”

Continuous Room‐Temperature Hydrogen Release from Liquid Organic Carriers in a Photocatalytic Packed‐Bed Flow Reactor

“…[6] Moreover, catalyst stability and recycling issues can further complicate the design of these processes. [7] Heterogeneous dehydrogenation catalysts that operate at temperatures higher than 120 °C and contain precious metal supported nanoparticles have been developed to address this issue at yields exceeding 95 %. In one example, Deraedt et al have shown that the dendrimer-stabilized nanoparticles of palladium (Pd), platinum (Pt), and rhodium (Rh) supported on SBA-15 silica can drive the dehydrogenation of 1,2,3,4-tetrahydroquinoline (THQ) to completion in 23 h at 130 °C.…”

“…N‐substituted heterocycles have lower dehydrogenation energy barrier when compared to cycloalkanes, and thus provide a low‐energy opportunity for H 2 release [6] . Moreover, catalyst stability and recycling issues can further complicate the design of these processes [7] . Heterogeneous dehydrogenation catalysts that operate at temperatures higher than 120 °C and contain precious metal supported nanoparticles have been developed to address this issue at yields exceeding 95 %.…”

Direct synthesis of triazines from alcohols and amidines using supported Pt nanoparticle catalysts via the acceptorless dehydrogenative methodology

“…[11][12][13][14] Several other triazines show wide-spread pharmacological activities as antiprotozoal, anticancer, antimalarial, antiviral, antimicrobial, antitumor, antituberculosis, anti HSV-1, and anti-HIV. [15][16][17] The literature is flooded with several reports of multicomponent triazine synthesis reactions with modifications in oxidants, solvents and starting materials. The development of methods using metal-mediated homogeneous catalysts for synthetic processes related to fine chemicals, such as flavors and pharmaceuticals, has been under attention in the last few years.…”

“…11–14 Several other triazines show wide-spread pharmacological activities as antiprotozoal, anticancer, antimalarial, antiviral, antimicrobial, antitumor, antituberculosis, anti HSV-1, and anti-HIV. 15–17…”