Hydrogen peroxide (H₂O₂), an environmental-friendly oxidant and renewable liquid fuel, has received wide attention in various research and industrial fields. Current industrial production of H₂O₂ relies on the anthraquinone method, which is hardly viewed as a sustainable and green process. Photocatalysis, harnessing solar energy as the driving force for redox reactions, provides a green and promising approach for H₂O₂ production. However, due to the poor ability of light absorption, fast recombination of carriers, and poor intrinsic activity of active sites of pristine photocatalysts, photocatalytic H₂O₂ production cannot provide great yield. Thus, great efforts have been dedicated to design efficient photocatalysts for photosynthesis of H₂O₂ in the past decades. In this review, we summarize significant progress in the development of advanced photocatalytic materials for light-driven H₂O₂ production. Starting with a brief introduction on basic principles and advantages of photosynthesis of H₂O₂, the representative materials are classified and discussed in detail; finally, a brief outlook on addressing future challenges and opportunities of photocatalytic H₂O₂ production is proposed. This review aims to confirm current challenges and research developments in the photosynthesis of H₂O₂ and provide inspiration for the development of high-efficiency photocatalysts for photocatalytic H₂O₂ production in the future.

Background: In our rapidly expanding society, the demand for clean water has steadily emerged as one of the most critical issues, promoting the development of numerous water treatment strategies.

Aims: Coupling photocatalysis and membrane separation technology provides an energy saving and environment-friendly as well as sustainable method for aqueous pollutants removal due to the synergetic enhanced pollutant removal efficiency and improved anti-fouling performance. It is of great scientific and technical significance to construct multifunctional photocatalysis-membrane separation reactor systems (PMRs) with both the high photocatalytic activity and the strong stability.

Discussion: Herein, in order to introduce the recent advances of this field, we present a critical review on developments of PMRs for aqueous pollutant removal, which includes photocatalysts and membranes, advanced methods for designing PMRs. Meanwhile, the recent applications of PMRs in aqueous pollutant removal, antifouling strategies, and mechanisms have also been summarized, including the latest development of PMRs coupling with other treatment methods. Furthermore, future perspective of PMRs is outlooked and predicted.

Conclusion: PMRs, designed for the removal of aqueous pollutants, offer a more promising solution for the sustainable development of our society in the future.

Background: Photochemical afterglow that relies on slow release of photons from the chemical energy stored by light pre-irradiation has emerged as a new optical imaging modality. However, conventional photochemical afterglow systems are considerably dependent on the interaction between multiple functional molecules, such as the afterglow initiator, the substrate, and the emitter. Therefore, these isolated functional molecules for afterglow luminescence have to be embedded in a nanoparticle with a confined space for many applications, which may suffer from problems like reproducibility and dye leakage.

Aim: Herein, we developed an “All-in-one” strategy that integrated all functional units for afterglow luminescence into one molecule to achieve photochemical afterglow of single organic small molecules.

Material & Methods: Triphenylamine and its derivatives contained single organic molecule were synthesized as “All-in-one” molecules, and underwent photo-chemical reactions triggered by singlet oxygen. We investigated the effect of substituents on the afterglow luminescence of the “All-in-one” molecules. Experimental measurements and theoretical calculations were performed to exhibit the wide-range tunable lifetimes and to reveal the involving mechanisms.

Results: By tailoring the electron-withdrawing ability of substituents, the afterglow lifetime of the “All-in-one” molecules can be conveniently tuned in a wide range from 28.6 s to 50.9 min. Moreover, the “All-in-one” afterglow materials were used to make smart printable security inks for optical multiplexing.

Discussion & Conclusion: Such “All-in-one” afterglow molecules successfully achieved bright afterglow with wide-range tunable lifetimes by the regulation of molecular structure according to the effect of substituents. This work provided a novel strategy to convert traditional fluorescent dyes into afterglow materials of single organic molecules and showed its great potential in multiple information encryption and advanced biological.

Hydrogen (H₂) energy is projected as a rising star to support the future society, and hydrogen peroxide (H₂O₂) is widely utilized as a raw material in medical and chemical fields. Photocatalytic water splitting might enable an entire and sustainable environment for natural H₂ evolution and concurrent H₂O₂ production, thus receiving increasing attention and realizing continuous achievements in recent years. However, such a reaction still suffers from the lacking of welldesigned photocatalytic systems with abundant active sites, and the efficiency is still far away from the standard of industrial-scale application. Benefiting from constant experimental and theoretical investigations, this choke point has been considered by constructing diverse photocatalysts with modulated electronic, chemical, and physical properties. In this sense, this review critically outlines the state-of-the-art progress on water splitting for H₂ and H₂O₂ production over discovered photocatalytic systems, including titanium dioxide, carbon nitride, metal sulfides, etc. The general principles, including the thermodynamics and kinetics analysis, emerging issues, and corresponding strategies, are discussed. Significantly, some lessons drawn from the previous literature concerning simultaneous H₂ and H₂O₂ production are proposed, and the main challenges in the future developments are summarized and clearly considered. This review aims to give a deep understanding of the photocatalytic water splitting for H₂ and H₂O₂ co-evolution and show some solutions to the future challenges in this field.

Background: Catalyst synthesis plays a crucial role in advancing photo and electrocatalysis technologies for sustainable development. However, the traditional thermal radiation heating method suffers from the disadvantages of high energy consumption, low heat transfer efficiency, slow heating speed and long heating time, which leads to the inefficiency and cost increases in catalyst preparation.

Aims: The Joule-heating ultrafast synthesis method with rapid heating/quenching and shorter heating time has attracted much attention. Despite its potential, there is a lack of comprehensive reviews specifically addressing the synthesis of advanced photo and electrocatalysts via Joule-heating. Therefore, this review aims to help people quickly understand the advantages of Joule-heating in the synthesis of photo and electrocatalysts.

Discussion: Herein, we firstly introduce the principles and devices of Jouleheating, and then we discuss breakthroughs in defect modulation, heterojunction construction, single-atom catalysts, bimetallic alloy catalysts, high-entropy alloy catalysts and metastable catalysts achieved through Joule-heating technology. The diverse applications of these catalysts include hydrogen evolution, oxygen evolution, oxygen reduction reactions, carbon dioxide reduction reactions, nitrogen reduction reaction and degradation of organic pollutants. Furthermore, this review provides a forward-looking perspective on future directions for employing Jouleheating methods in the field of photo and electrocatalysis research.

Conclusion: This review highlights the pivotal role played by Joule-heating techniques in advancing nanomaterial synthesis as well as developing sustainable high-performance catalyst systems.