Theoretical calculations reveal that intrinsic pentagons in the basal plane can contribute to the local electronic redistribution and the contraction of band gap, making the carbon matrix possess superior binding affinity and electrochemical reactivity. To experimentally verify this, a pentagon‐defect‐rich carbon nanomaterial was constructed by means of in situ etching of fullerene molecules (C60). The electrochemical tests show that, relative to hexagons, such a carbon‐based material with abundant intrinsic pentagon defects makes much greater contribution to the electrocatalytic oxygen reduction activity and electric double layer capacitance. It shows a four‐electron‐reaction mechanism similar to commercial Pt/C and other transition‐metal‐based catalysts, and a higher specific capacitance than many reported metal‐free carbon materials. These results show the influence of intrinsic pentagon defects for developing carbon‐based nanomaterials toward energy conversion and storage devices.

Developing highly efficient and stable electrocatalysts plays an important role in energy-related electrocatalysis fields. Transition-metal phosphides (TMPs) possess a series of advantages, such as high conductivity, earthabundance reserves, and good physicochemical properties, therefore arousing wide attention. In this review, the electrochemical activity origin of TMPs, allowing the rational design and construction of phosphides toward various energy-relevant reactions is first discussed. Subsequently, their unique energy-related electrocatalysis nature toward hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR), carbon dioxide reduction reaction (CO 2 RR), nitrogen reduction reaction (NRR), urea oxidation reaction (UOR), methanol oxidation reaction (MOR), and others is highlighted. Then, the TMPs' synthetic strategies are analyzed and summarized systematically. Finally, the existing key issues, countermeasures, and the future challenges of TMPs toward efficient energy-related electrocatalysis are briefly discussed.

Theoretical calculations unveil the charge redistribution over abundant interfaces and the enhanced electronic states of Ru/RuS2 heterostructure. The resulting surface electron‐deficient Ru sites display optimized adsorption behavior toward diverse reaction intermediates, thereby reducing the thermodynamic energy barriers. Experimentally, for the first time the laminar Ru/RuS2 heterostructure is rationally engineered by virtue of the synchronous reduction and sulfurization under eutectic salt system. Impressively, it exhibits extremely high catalytic activity for both OER (201 mV @ 10 mA cm−2) and HER (45 mV @ 10 mA cm−2) in acidic media due to favorable kinetics and excellent specific activity, consequently leading to a terrific performance in acidic overall water splitting devices (1.501 V @ 10 mA cm−2). The in‐depth insight into the internal activity origin of interfacial effect could offer precise guidance for the rational establishment of hybrid interfaces.

HIGHLIGHTS• All the important single-atom catalysts (SACs) synthetic strategies, such as wet-chemistry method, atomic layer deposition, metalorganic framework-derived method, electrodeposition, high-temperature atom trapping from bulk particles, and vacancies/defects immobilized strategy, have been summarized and discussed in detail.• Various metal-based (especially Pt, Pd, Ru, Fe, Co, Ni, Mo, W, V) SACs in electrocatalytic hydrogen evolution reaction (HER) have been systematically reviewed.• The current key challenges in SACs for electrochemical HER are pointed out, and some potential strategies/perspectives are proposed.ABSTRACT Hydrogen, a renewable and outstanding energy carrier with zero carbon dioxide emission, is regarded as the best alternative to fossil fuels. The most preferred route to large-scale production of hydrogen is by water electrolysis from the intermittent sources (e.g., wind, solar, hydro, and tidal energy). However, the efficiency of water electrolysis is very much dependent on the activity of electrocatalysts. Thus, designing high-effective, stable, and cheap materials for hydrogen evolution reaction (HER) could have a substantial impact on renewable energy technologies. Recently, single-atom catalysts (SACs) have emerged as a new frontier in catalysis science, because SACs have maximum atom-utilization efficiency and excellent catalytic reaction activity.Various synthesis methods and analytical techniques have been adopted to prepare and characterize these SACs. In this review, we discuss recent progress on SACs synthesis, characterization methods, and their catalytic applications. Particularly, we highlight their unique electrochemical characteristics toward HER. Finally, the current key challenges in SACs for HER are pointed out and some potential directions are proposed as well. E le c tr on m ic ro s co py MO F-W e t-C h e m is t r y AL D De rived Sp ec tr o s c o p y te ch n iq u e H ER Im m o b il iz ed ato m tr ap p in g d e po sit ion E le ct ro-S iO 2

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