Hydrogen spillover (HSo) has emerged to upgrade the hydrogen evolution reaction (HER) activity of Pt‐support electrocatalysts, but it is not applicable to the deprotonated oxygen evolution reaction (OER). Non‐precious catalysts that can perform well in both HSo and deprotonation (DeP) are extremely desirable for a sustainable hydrogen economy. Herein, an affordable MoS2/NiPS3 vertical heterostructure catalyst is presented to synergize HSo and DeP for efficient water electrolysis. The internal polarization field (IPF) is clarified as the driving force of HSo in HER electrocatalysis. The HSo from the MoS2 edge to NiPS3 can activate the NiPS3 basal plane to boost the HER activity of the MoS2/NiPS3 heterostructure (112 mV vs reversible hydrogen electrode (RHE) at 10 mA cm–2), while for OER, the IPF in the heterostructure can facilitate the hydroxyl diffusion and render MoS2‐to‐NiPS3/P‐to‐S dual‐pathways for DeP. As a result, the stacking of OER‐inactive MoS2 on the NiPS3 surface still brings intriguing OER enhancements. With them serving as electrode couples, the overall water splitting is attested stably with a cell voltage of 1.64 V at 10 mA cm−2. This research puts forward the IPF as the criterion in the rational design of HSo/DeP‐unified non‐precious catalysts for efficient water electrolysis.

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Electrocatalytic splitting of water holds the fossil-free premise for H 2 production, which couples cathodic hydrogen and anodic oxygen evolution reactions (HER/OER). [1] Kinetically driving water electrolysis (WE) requires efficient and stable catalysts to reduce the overpotentials for both HER and OER. [2] During practical WE operations, the electrolyte's pH change is a critical challenge for the activity and stability retention of the electrocatalysts. [3] Therefore, there is an urgent need to develop robust electrocatalysts for wide pH conditions to ensure work efficiency and reduce usage costs. Although Pt-group metals are endowed with active and pH-robust HER/OER properties, the costliness and scarcity greatly limit their sustainable deployments in WE. [4] In this regard, rationalizing non-precious pHrobust catalysts is the top priority of current research for water splitting. Electronic level adjustment is the fundamental technique for the rational design of advanced non-precious catalysts. [5] As known, the d-band (ε d ) and p-band center (ε p ) to Fermi level can well reflect the intermediates' adsorption energies and activation energy barriers during HER/ OER catalysis. [6] Currently, the d-band center level of 3d-metal sites is widely considered to be effective descriptors for HER and OER. [5a] However, the metal sites are not the actual active catalytic centers in some systems, [6c] and the p-band center of non-metal atoms should be revisited together with ε d . Hence, the synergic tuning of d/p-band center will be the design criterion for the innovation of economic, robust, and efficient WE catalysts.Interface engineering is deemed as an effective measure to achieve the d-band center regulation in terms of the interfacial charge transfer between the components. [7] In addition, the heterostructure can exhibit the protection and lattice confinement effect on the surface active atoms, modifying the stability and electronic structure by lattice distortion. [8] Current reports on transition metal heterostructures are mainly crystalline-crystalline complexes, and the interfacial atomic distortion will be hindered by lattice resistance or structural rigidity to some extent. [9] In this context, the establishment of an amorphous-crystalline Rationalizing non-precious pH-robust electrocatalysts is a crucial priority and required for multi-scenario hydrogen production customization. Herein, an amorphous-crystalline CoBO x /NiSe heterostructure is theoretically profiled and constructed for efficient and pH-robust water electrolysis. The crystalline lattice confinement induces a CoCo bond shortening and a B-site delocalization on amorphous CoBO x , resulting in a decreased d-p band center difference (Δε d-p ) toward the balanced intermediates adsorption/desorption. Accordingly, the CoBO x /NiSe heterostructure exhibits efficient and robust hydrogen/oxygen evolution reaction (HER/OER) catalytic activity in different electrolytes. Of particular note, it achieves ultralow overpotentials in both the beyon...

The development of advanced energy storage and conversion technology is a significant global concern, in which the innovation in materials would feature prominently for next-generation energy devices. Graphene, as a typical two-dimensional (2D) material, is acknowledged to have a significant impact on today's energy-storage/ conversion evolution. The effectuation for future energy landscape should still enlist alternative 2D materials with high electrochemical activity and energy density. As a group of 2D nanomaterials, metallene is considered as a potential candidate because of its fantastic physicochemical properties. In this Review, the structures, synthesis strategies, and properties of various metallenes are systematically introduced. The research progress and latest achievements in the energy field are reviewed, including Li-/Na-/K-ion batteries, Li−S batteries, solar cells, and typical catalytic processes (i.e., CO 2 /N 2 /O 2 reduction reaction, hydrogen/oxygen evolution reaction, etc.). Besides, the challenges of miscellaneous energy storage/conversion devices and the advantages of applications of metallenes are discussed and compared. Finally, the development prospects are provided as suggested guidelines for future researches.

Highlights This review introduces recent advances of various anion-mixed transition metal compounds (e.g., nitrides, halides, phosphides, chalcogenides, (oxy)hydroxides, and borides) for efficient water electrolysis applications in detail. The challenges and future perspectives are proposed and analyzed for the anion-mixed water dissociation catalysts, including polyanion-mixed and metal-free catalyst, progressive synthesis strategies, advanced in situ characterizations, and atomic level structure–activity relationship. Abstract Hydrogen with high energy density and zero carbon emission is widely acknowledged as the most promising candidate toward world's carbon neutrality and future sustainable eco-society. Water-splitting is a constructive technology for unpolluted and high-purity H2 production, and a series of non-precious electrocatalysts have been developed over the past decade. To further improve the catalytic activities, metal doping is always adopted to modulate the 3d-electronic configuration and electron-donating/accepting (e-DA) properties, while for anion doping, the electronegativity variations among different non-metal elements would also bring some potential in the modulations of e-DA and metal valence for tuning the performances. In this review, we summarize the recent developments of the many different anion-mixed transition metal compounds (e.g., nitrides, halides, phosphides, chalcogenides, oxyhydroxides, and borides/borates) for efficient water electrolysis applications. First, we have introduced the general information of water-splitting and the description of anion-mixed electrocatalysts and highlighted their complementary functions of mixed anions. Furthermore, some latest advances of anion-mixed compounds are also categorized for hydrogen and oxygen evolution electrocatalysis. The rationales behind their enhanced electrochemical performances are discussed. Last but not least, the challenges and future perspectives are briefly proposed for the anion-mixed water dissociation catalysts.

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Layered metal dichalcogenides (LMDs) have been acknowledged as having an efficient gas-sensing process because of their tunable electronic structure and active edge sites. However, the full operation of their sensing properties is greatly hindered by the inactive basal plane of LMD and thus could possibly be considered by deblocking the basal plane. Herein, defective SnS 2 nanosheets were synthesized via a facile solvothermal process with subsequent argon plasma irradiation in just several seconds and have been exploited for NH 3 gas-sensing applications. A large number of surface defects on SnS 2 nanosheets were produced by plasma treatment and tailored by the irradiation time to modulate the electronic structure. It is found that SnS 2 nanosheets after 4 s of Ar plasma treatment exhibit promising NH 3 -sensing properties including high sensitivity, superior selectivity, and promoted sensing kinetics as well as low operation temperature. A five-axe spider-web diagram was also established for the evaluation of suitable operation condition. Furthermore, density functional theory calculations were conducted to reveal the rationales behind the defect-enhanced sensing behaviors. The results suggest that the efficient NH 3 detection and NH 3 adsorption transient from physi-to chemisorption mechanism are dominated by the S-vacancy defects on the basal plane. This work may open up interesting horizons for rational design of the LMD-based materials with promising sensing behaviors through defect engineering.

The catalyst innovation that aims at noble‐metal‐free substitutes is one key aspect for future sustainable hydrogen energy deployment. In this paper, a nickel cobalt sulfoselenide/black phosphorus heterostructure (NiCoSe|S/BP) was fabricated to realize the highly active and durable water electrolysis through interface and valence dual‐engineering. The NiCoSe|S/BP nanostructure was constructed by in‐situ growing NiCo hydroxide nanosheet arrays on few‐layer BP and subsequently one‐step sulfoselenization by SeS2. Besides the conductive merit of BP substrate, holes in p‐type BP are capable of oxidizing the Co2+ to high‐valence and electron‐accepting Co3+, benefiting the oxygen evolution reaction (OER). Meanwhile, Ni3+/Ni2+ ratio in the heterostructure is reduced to maintain the electrical neutrality, which corresponds to the increased electron‐donating character for boosting hydrogen evolution reaction (HER). As for HER and OER, the heterostructured NiCoSe|S/BP electrocatalyst exhibits small overpotentials of 172 and 285 mV at 10 mA cm−2 (η10) in alkaline media, respectively. And overall water splitting has been achieved at a low cell potential of 1.67 V at η10 with high stability. Molecular sensing and density functional theory (DFT) calculations are further proposed for understanding the rate‐determine steps and enhanced catalytic mechanism. The investigation presents a deep‐seated perception for the electrocatalytic performance enhancement of BP‐based heterostructure.