Photoreduction of N₂ is among the most interesting and challenging methods for N₂ fixation under mild conditions. In this study, we determined that nitrogen vacancies (NVs) could endow graphitic carbon nitride (g-C₃N₄) with the photocatalytic N₂ fixation ability. Photocatalytic N₂ fixation induced by NVs is free from the interference of other gases. The reason is that NVs could selectively adsorb and activate N₂ because NVs have the same shape and size as the nitrogen atom in N₂. In addition to this, NVs could also improve many other properties of g-C₃N₄ to support photocatalytic N₂ fixation. These new findings could elucidate the design of efficient photocatalysts for photocatalytic N₂ fixation.

Selective photocatalytic N₂ fixation dependent on g-C₃N₄ induced by nitrogen vacancies

Merging hydrogen (H2) evolution with oxidative organic synthesis in a semiconductor-mediated photoredox reaction is extremely attractive because the clean H2 fuel and high-value chemicals can be coproduced under mild conditions using light as the sole energy input. Following this dual-functional photocatalytic strategy, a dreamlike reaction pathway for constructing C-C/C-X (X = C, N, O, S) bonds from abundant and readily available X-H bond-containing compounds with concomitant release of H2 can be readily fulfilled without the need of external chemical reagents, thus offering a green and fascinating organic synthetic strategy. In this review, we begin by presenting a concise overview on the general background of traditional photocatalytic H2 production and then focus on the fundamental principles of cooperative photoredox coupling of selective organic synthesis and H2 production by simultaneous utilization of photoexcited electrons and holes over semiconductor-based catalysts to meet the economic and sustainability goal. Thereafter, we put dedicated emphasis on recent key progress of cooperative photoredox coupling of H2 production and various selective organic transformations, including selective alcohol oxidation, selective methane conversion, amines oxidative coupling, oxidative cross-coupling, cyclic alkanes dehydrogenation, reforming of lignocellulosic biomass, and so on. Finally, the remaining challenges and future perspectives in this flourishing area have been critically discussed. It is anticipated that this review will provide enlightening guidance on the rational design of such dual-functional photoredox reaction system, thereby stimulating the development of economical and environmentally benign solar fuel generation and organic synthesis of value-added fine chemicals.

Cooperative Coupling of Oxidative Organic Synthesis and Hydrogen Production over Semiconductor-Based Photocatalysts.

MXene-based photocatalysts

Photocatalytic degradation of tetracycline antibiotic by a novel Bi2Sn2O7/Bi2MoO6 S-scheme heterojunction: Performance, mechanism insight and toxicity assessment

3D graphene-based gel photocatalysts for environmental pollutants degradation.

The development of efficient catalyst for photoredox-catalyzed selective organic synthesis has always been remaining the attractive objective in recent years. Regarding semiconductor-based photocat...

Selective Organic Transformations over Cadmium Sulfide-Based Photocatalysts

Exploiting solar energy to photocatalyze integrated selective conversion of bioethanol into fine chemicals and hydrogen (H2) is a promising avenue in response to current energy and environmental crises. Herein, we have reported the mild synthesis of a binary heterostructure of CdS-Ti3C2Tx MXene (CdS-MX) combining one-dimensional (1D) CdS nanowires (NWs) with two-dimensional (2D) MXene structure, and its application in photocatalytic coupling redox reaction of H2 evolution and selective conversion of bioethanol into 1,1-diethoxyethane (DEE) under acidic conditions. The results reveal that the synergistic effect of the intimate interfacial contact and matched energy level alignment between electrically conductive 2D MXene and semiconductor 1D CdS NWs benefits the separation and migration of charge carriers. Furthermore, CH(OH)CH3 has been proven to be the pivotal radical intermediate during photoredox process. This work is anticipated to stimulate further interest on rational construction of MXene-semiconductor based composites toward photoredox coupling organic synthesis and H2 evolution in a sustainable manner.

Visible-light-driven integrated organic synthesis and hydrogen evolution over 1D/2D CdS-Ti3C2Tx MXene composites

Photoredox-catalyzed biomass intermediate conversion integrated with H2 production over Ti3C2Tx/CdS composites

Artificial photocatalytic N2 reduction to NH3 under ambient conditions represents a promising alternative way for the industrial N2 fixation by Haber − Bosch process. This work reports the simultaneous engineering of BiOBr nanosheets with exposed {102} facets by means of transition metal (Fe, Mo, Ni) doping and oxygen vacancies (OVs) that aid to expose internal metal dopants toward efficient visible light N2 fixation. The synergy of transition metal doping and OVs results in the modulated band structures, improved charge carrier separation as well as electron transfer to N2, thereby leading to enhanced N2 adsorption and activation ability over modified BiOBr nanosheets. In particular, the Fe-doped BiOBr with OVs possesses the optimal photocatalytic activity of NH3 yield of 46.1 μmol g–1 h–1 without any sacrificial agent, which is 6-fold that of pristine BiOBr. The findings will shed new light on rational engineering of adsorption, activation sites and charge carrier separation for designing efficient N2 fixation photocatalysts.

Jing-Yu Li

Papers

3D graphene-based gel photocatalysts for environmental pollutants degradation.

Selective Organic Transformations over Cadmium Sulfide-Based Photocatalysts

Visible-light-driven integrated organic synthesis and hydrogen evolution over 1D/2D CdS-Ti3C2Tx MXene composites

Photoredox-catalyzed biomass intermediate conversion integrated with H2 production over Ti3C2Tx/CdS composites

Transition metal doping BiOBr nanosheets with oxygen vacancy and exposed {102} facets for visible light nitrogen fixation