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The development of highly active and selective photocatalytic systems for the oxidation of benzylic C(sp3)–H and C(sp3)–OH to C＝O bonds under solvent-free conditions with molecular oxygen as an oxidant is attractive and challenging. In this study, a carbon- and PdO-doped Nb2O5-based catalyst (PdO/C–Nb2O5) was designed and synthesized. This photocatalyst showed excellent solvent-free aerobic photocatalytic performances for two typical oxidation reactions of benzylic C(sp3)–H and C(sp3)–OH to C＝O compounds. It was found that the doping of carbon and PdO in Nb2O5 can modify its surface electrons, increase oxygen vacancies, and change the positions of its valence band and conduction band. Besides, the kinetic study showed that the oxidation of C–H in ethylbenzene to C–OH is the rate-limiting step in the two-step oxidation of ethylbenzene to acetophenone. Moreover, a photocatalytic reaction mechanism was proposed based on these experiments. In addition, the solvent-free aerobic photocatalytic oxidation system showed a good substrate tolerance for benzylic C(sp3)–H and C(sp3)–OH compounds with different substituents to the corresponding ketones and aldehydes. [ABSTRACT FROM AUTHOR]

Imines are vital intermediate chemicals applied in organic synthesis, pharmaceuticals, and materials science. It is desirable but challenging to explore a green photocatalytic system, especially solvent-free photocatalysis, for the synthesis of imines from amines with molecular oxygen as an oxidant under mild reaction conditions. In the present study, a ternary CdS/Ag/BiVO4 Z-heterojunction photocatalyst was designed and prepared for the photocatalytic oxidative coupling of benzylamine to N-benzylidenebenzylamine. Under solvent-free conditions, a yield of 92% of N-benzylidenebenzylamine with a selectivity of 99% was achieved over CdS/Ag/BiVO4 in neat benzylamine with dioxygen as an oxidant at room temperature and ambient pressure. In the Z-scheme electronic transmission system, CdS worked as a reductive photocatalyst, while BiVO4 acted as an oxidative photocatalyst. The oxygen vacancies in the catalyst and Ag nanoparticles in the catalyst with their plasmonic effect boosted light absorption, enhancing charge migration and photogenerated electron–hole separation on the contact interface. A photocatalytic mechanism was proposed based on controlled experiments. The catalyst exhibited good stability for five cycles, and the catalyst can be applied for the oxidative coupling of various amines to imines. This work provides a strategy for the rational design of photocatalytic oxidative coupling of amines to imines. [ABSTRACT FROM AUTHOR]

The advancement of cost-effective and highly efficient electrocatalysts for hydrogen evolution is pivotal in fostering the progress of clean energy technologies. In this study, we present a reforming approach aimed at facile fabrication of the Cr-CeO2/rGO electrocatalyst. This involves incorporating a limited quantity of reduced graphene oxide (rGO) to serve as a conductive scaffold for CeO2 nanocrystals (NCs) while also introducing Cr, a transition metal, as an active dopant. It is found that the introduction of Cr and rGO induces charge transfer, leading to enhanced electrical conductivity and the creation of additional active sites on the nanocomposite surface. The synergy between rGO and CeO2, along with Cr doping in CeO2, significantly improves HER performance. The representative sample of the Cr(5%)-CeO2/rGO catalyst demonstrates a low overpotential of 83 mV at a current density of 10 mA cm–2, a low Tafel slope of 81 mV dec–1, and excellent stability under alkaline conditions. Significantly, this value of overpotential is reduced by 81 and 127 mV compared to those of the CeO2/rGO nanocomposites and the pristine CeO2 NCs. Theoretical density functional theory calculations additionally validate the phenomenon of charge transfer and improved HER properties, with Cr-CeO2 displaying a favorable Gibbs free energy (ΔGH*) for H* adsorption. This study offers novel insights into the design of precious metal electrocatalysts featuring functional interfaces and a wealth of active sites, holding great promise for industrial applications in clean energy conversion and storage. [ABSTRACT FROM AUTHOR]

In this review, we summarize the important progress in the electroreduction of N2 to NH3 using state-of-the-art two-dimensional (2D) electrocatalysts. We expound on several reaction mechanisms of the nitrogen reduction reaction (NRR) and report recent experimental progress regarding these unique 2D NRR electrocatalysts. In addition, some concepts recently proposed from high-throughput computations and machine learning are described. By building on a detailed understanding of the process of N2 conversion to NH3 on 2D electrocatalysts, novel 2D materials that could potentially serve as viable NRR electrocatalysts are presented. Future perspectives and challenges of N2 electrolysis using 2D materials are also discussed. [ABSTRACT FROM AUTHOR]