Advances in liquid organic hydrogen carriers: developing efficient dehydrogenation strategies.

In pursuit of global carbon neutrality, countries are intensifying their efforts to harness clean energy sources. Hydrogen emerges as a superior alternative to traditional fossil fuels and plays a crucial role in the global energy shift. Liquid Organic Hydrogen Carrier (LOHC) systems are lauded for their high hydrogen storage capacity, ease of handling, and safe and efficient transportation, positioning them as effective solutions for extensive hydrogen storage and international distribution. Nevertheless, the dehydrogenation of hydrogen-rich LOHCs is slow, requiring high temperatures and substantial energy inputs. Addressing these challenges by reducing energy demands and improving dehydrogenation rates is essential for advancing LOHC technology. This paper comprehensively examines various LOHC systems, focusing on the selection of carriers and dehydrogenation catalysts, and their dehydrogenation efficacy. It also highlights our recent contributions in photocatalytic LOHC and outlines future research directions to enhance LOHC technology.

Liberating C-H Bond Activation: Achieving 56% Quantum Efficiency in Photocatalytic Cyclohexane Dehydrogenation.

The technology of liquid organic hydrogen carriers presents great promise for large-scale hydrogen storage. Nevertheless, the activation of inert C(sp3)-H bonds in hydrocarbon carriers poses formidable challenges, resulting in a sluggish dehydrogenation process and necessitating high operating temperatures. Here, we break the shackles of C-H bond activation under visible light irradiation by fabricating subnanometer Pt clusters on defective Ce-Zr solid solutions. We achieved an unprecedented hydrogen production rate of 2601 mmol gcat.-1 h-1 (turnover frequency >50,000 molH2 molPt-1 h-1) from cyclohexane, surpassing the most advanced thermo- and photocatalysts. By optimizing the temperature-dominated hydrogen transfer process, achievable by harnessing hitherto wasted infrared light in sunlight, an astonishing 56% apparent quantum efficiency and a 5.2% solar-to-hydrogen efficiency are attained at 353 K. Our research stands as one of the most effective photocatalytic processes to date, holding profound practical significance in the utilization of solar energy and the exploitation of alkanes.

Defect Pyrochlore-Type Mott-Schottky Photocatalysts for Enhanced Ammonia Synthesis at Low Pressure.

The ambient ammonia synthesis coupled with distributed green hydrogen production technology can provide promising solutions for low-carbon NH3 production and H2 storage. Herein, we reported Ru-loaded defective pyrochlore K2 Ta2 O6-x with remarkable visible-light absorption and a very low work function, enabling effective visible-light-driven ammonia synthesis from N2 and H2 at low pressure down to 0.2 atm. The photocatalytic rate was 2.8 times higher than that of the best previously reported photocatalyst and the photo-thermal rate at 425 K was similar to that of Ru-loaded black TiO2 at 633 K. Compared to perovskite-type KTaO3-x with the same composition, the pyrochlore exhibited a 3.7-fold increase in intrinsic activity due to a higher photoexcited charge separation efficiency and a higher conduction band position. The interfacial Schottky barrier and spontaneous electron transfer between K2 Ta2 O6-x and Ru further improve photoexcited charge separation and accumulate energetic electrons to facilitate N2 activation.