Recent progress made in the prediction, characterisation, and mitigation of multipactor discharge is reviewed for single‐ and two‐surface geometries. First, an overview of basic concepts including secondary electron emission, electron kinetics under the force law, multipactor susceptibility, and saturation mechanisms is provided, followed by a discussion on multipactor mitigation strategies. These strategies are categorised into two broad areas – mitigation by engineered devices and engineered radio frequency (rf) fields. Each approach is useful in different applications. Recent advances in multipactor physics and engineering during the past decade, such as novel multipactor prediction methods, understanding space charge effects, schemes for controlling multipacting particle trajectories, frequency domain analysis, high frequency effects, and impact on rf signal quality are presented. In addition to vacuum electron multipaction, multipactor‐induced ionization breakdown is also reviewed, and the recent advances are summarised.

Hydrogen generated by water electrolysis is considered as one of the most promising protocols to partly replace the roles of traditional fossil fuels. However, high‐performance electrocatalyst satisfied with the industrial requirement still faces significant challenges. Low‐temperature plasma contains numerous high‐energy ions, electrons and other reactive species, which can provide a highly reactive environment for tuning the physio‐chemical structures of catalysts through plasma milling, etching, doping and/or deposition. It is well‐known that high‐temperature micro‐filaments contained in plasmas can cause some special modifications of the catalyst surface, thus effectively adjusting the physio‐chemical structure of latterly engineered compounds. Therefore, low‐temperature plasma technologies, especially the dielectric barrier discharge (DBD) and radio frequency (RF) plasmas, can be considered as a green and sustainable strategy for engineering high‐performance electrocatalysts for water splitting (hydrogen evolution reaction [HER]; oxygen evolution reaction [OER]). Herein, recent progress of DBD and RF plasmas for fabricating and modifying transition metal‐based electrocatalysts (e.g. sulphide, phosphide, selenide, oxide, hydroxide) for hydrogen evolution reaction or OER is comprehensively reviewed, and the role of plasma is also discussed.

Dielectric barrier discharges (DBD) are widely utilised non‐equilibrium atmospheric pressure plasmas with a diverse range of applications, such as material processing, surface treatment, light sources, pollution control, and medicine. Over the course of several decades, extensive research has been dedicated to the generation of homogeneous DBD (H‐DBD), focussing on understanding the transition from H‐DBD to filamentary DBD and exploring strategies to create and sustain H‐DBD. This paper first discusses the influence of various parameters on DBD, including gas flow, dielectric material, surface conductivity, and mesh electrode. Secondly, a chronological literature review is presented, highlighting the development of H‐DBD and the associated understanding of its underlying mechanisms. This encompasses the generation of H‐DBD in helium, nitrogen, and air. Lastly, the paper provides a brief overview of multiple‐current‐pulse (MCP) behaviours in H‐DBD. The objective of this article is to provide a chronological understanding of homogeneous dielectric barrier discharge (DBD). This understanding will aid in the design of new experiments aimed at better comprehending the mechanisms behind H‐DBD generation and ultimately assist in achieving large‐volume H‐DBD in an air environment.

The physical mechanism of leader formation and development is not well understood. In this study, we present experimental and simulation results obtained with a 10 m long air gap discharge. A 10 m outdoor discharge experiment is carried out to obtain the current, voltage, and optical image during the leader discharge process. Four different impulse voltages were applied to the rod‐plane gap. The measured current is used as an input for a plasma model, then the temperature and electric field could be calculated. The simulation results show that the temperature of the streamer stem during the dark period may exceed 2000 K. In addition, the critical charge required for leader initiation can be as low as 0.27 μC for a 10 m air gap. The channel temperature is relatively stable in the process of leader development, which is maintained at about 4500 K. The electron density is about 0.5–3 × 10²⁰ m⁻³, and the discharge channel conductivity fluctuates in the range of 1–10 S/m for the leader current between 1 and 2 A. A long dark period is tended to be associated with a higher injected charge by the first streamer. It is inferred that the voltage increments during the dark period play an important role in promoting streamer‐to‐leader transition, except for temperature and the injected charge.