Jiawei Song

Hydrogen peroxide (H2O2), an ecofriendly oxidant, is extensively employed in wastewater treatment, pulp bleaching, and chemical synthesis. Photocatalytic 2e– oxygen reduction reaction (2e– ORR) to H2O2 has emerged as a renewable strategy for solar-to-chemical energy conversion. Carbon nitride (CN) is a promising candidate for producing H2O2 due to its unique optical properties and electronic structure. However, the ambiguity of the reaction mechanism still limits the development of photocatalytic H2O2 production because of the complexity of the reaction active sites. Previous research on the reaction mechanism was not deep enough, leading to the actual role of reaction sites being relatively indistinct in the photocatalytic process. This Review systematically explores the intrinsic mechanism of enhancing the performance of photocatalysts, with a focus on analyzing the action mechanism of multiple types of active sites (such as defect sites, doping sites, surface metal sites, etc.) induced by different modification strategies in 2e– ORR, which provides a theoretical basis for elucidating the structure–activity relationship of different active sites and their key role in selective H2O2 production. Furthermore, the challenges, opportunities, and future research directions of photocatalytic 2e– ORR for H2O2 production have also been emphasized. This work breaks through the conventional research mode of “modification earlier, analysis later” in traditional photocatalytic materials, innovatively explaining the structure–activity relationships of different types of reaction sites in photocatalytic H2O2 production from the perspective of reaction sites. This “mechanism-driven rational design strategy” based on reaction mechanism reverse design of catalytic sites provides a theoretical framework for breaking through the limitations of traditional trial and error approaches in photocatalyst optimization, especially in guiding the functional modification of inefficient catalysts.

Abstract Semiconductor heterojunctions can significantly enhance the separation of photogenerated charge carriers, among which Z‐type heterojunctions are more conducive to photocatalysis due to their special transfer paths and strong oxidizing and reducing properties. However, introducing efficient active sites has always been a significant challenge in the improvement of heterogeneous photocatalysts. Herein, through in‐depth analysis of the reaction mechanism and structural characteristics, single atom catalysts and heterojunctions are ingeniously integrated using built‐in electric fields. For the first time, the suitable metal single atom active sites are successfully designed under the special electronic structure at the N‐terminal, utilizing low electronegativity non‐metallic element doping to counteract local electron migration from heterojunctions. Ladder‐like built‐in electric field composed of the divergent and parallel built‐in electric fields from single atom catalysts and heterojunctions respectively, which introduces a new carrier separation path. AgPCN/BCN heterojunction reaches a hydrogen peroxide (H 2 O 2 ) yield 559.5 µM∙h −1 and an apparent quantum efficiency of 17.8% through 2e − oxygen reduction reaction. Photoelectrochemical tests indicate the importance of 4e − water oxidation reaction as an auxiliary reaction. This novel and innovative photocatalyst structure brings new approaches for photocatalysts improvement, and new insights into the role of built‐in electric fields in photocatalytic reaction mechanisms.

Filamentary-type resistive switching devices, such as conductive bridge random-access memory and valence change memory, have diverse applications in memory and neuromorphic computing. However, the randomness in filament formation poses challenges to device reliability and uniformity. To overcome this issue, various defect engineering methods have been explored, including doping, metal nanoparticle embedding, and extended defect utilization. In this study, we present a simple and effective approach using self-assembled uniform Au nanoelectrodes to controll filament formation in HfO2 resistive switching devices. By concentrating the electric field near the Au nanoelectrodes within the BaTiO3 matrix, we significantly enhanced the device stability and reduced the threshold voltage by up to 45% in HfO2-based artificial neurons compared to the control devices. The threshold voltage reduction is attributed to the uniformly distributed Au nanoelectrodes in the insulating matrix, as confirmed by COMSOL simulation. Our findings highlight the potential of nanostructure design for precise control of filamentary-type resistive switching devices.