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Oxygen evolution reaction (OER) under acidic conditions becomes of significant importance for the practical use of a proton exchange membrane (PEM) water electrolyzer. In particular, maximizing the mass activity of iridium (Ir) is one of the maiden issues. Herein, the authors discover that the Ir‐doped calcium copper titanate (CaCu₃Ti₄O₁₂, CCTO) perovskite exhibits ultrahigh mass activity up to 1000 A gIr−1 for the acidic OER, which is 66 times higher than that of the benchmark catalyst, IrO2. By substituting Ti with Ir in CCTO, metal‐oxygen (M‐O) covalency can be significantly increased leading to the reduced energy barrier for charge transfer. Further, highly polarizable CCTO perovskite referred to as "colossal dielectric", possesses low defect formation energy for oxygen vacancy inducing a high number of oxygen vacancies in Ir‐doped CCTO (Ir‐CCTO). Electron transfer occurs from the oxygen vacancies and Ti to the substituted Ir consequentially resulting in the electron‐rich Ir and ‐deficient Ti sites. Thus, favorable adsorptions of oxygen intermediates can take place at Ti sites while the Ir ensures efficient charge supplies during OER, taking a top position of the volcano plot. Simultaneously, the introduced Ir dopants form nanoclusters at the surface of Ir‐CCTO, which can boost catalytic activity for the acidic OER. [ABSTRACT FROM AUTHOR]

Summary: Alkaline oxygen evolution reaction (OER) electrocatalysts have been widely studied for improving the efficiency and green hydrogen production through electrochemical water splitting. Currently, iron‐doped nickel‐LDHs (NF‐LDHs) are regarded as the benchmark electrocatalyst for alkaline OER, primarily owing to the physicochemical synergetic effects between Ni and Fe. Here, the third element addition into NF‐LDHs is designed to further enhance the electrocatalytic performance through the modulation of electronic property. Cu‐doped NF‐LDHs (NFC‐LDHs) are developed with the self‐supported structure on porous supports. NFC‐LDHs can be grown on carbon cloth (CC) in an intriguing 2D nanosheet structure, wherein the surface electronic configuration is suitably modulated by interactions among Ni‐Fe‐Cu. Importantly, activation energy for OER can be lowered by adding Cu into NF‐LDHs. Thereby, the NFC‐LDHs exhibited enhanced OER activity and improved stability than those of nickel‐LDHs (Ni‐LDHs) and NF‐LDHs. For NFC‐LDHs, small overpotentials of only 230 and 250 mV yield current densities of 50 and 100 mA cm−2, respectively. In addition, excellent electrochemical stability is demonstrated during long‐term OER tests without any degradation demonstrating no dissolution of active metals water electrolysis due to synergetic effects among Ni‐Fe‐Cu. [ABSTRACT FROM AUTHOR]

Summary: There is a need to develop highly efficient electrocatalysts based on non‐noble metals which can be used for water splitting. Thus, to realize an acceptable oxygen evolution reaction (OER) performance, a combination of non‐noble metals was used to improve the architecture and conducive to a facile OER. For this purpose, a binder‐free and non‐noble metal‐based trimetallic (CuZnAg) composite OER a electrocatalyst was grown at the surface of fluorine‐doped tin oxide by a facile one step in‐situ electrodeposition method using chronoamperometry. The formation and performance of the catalyst were ensured from XRD, SEM, EDX, chronoamperometry, and linear scan voltammetry. The trimetallic composite showed good results toward OER in 1 M KOH electrolyte at pH 13 at a current density of 1 mA/cm2 with an overpotential of 303 mV at a scan rate of 10 mV/sec. The results revealed robust electrochemical durability under alkaline conditions and the electrocatalyst holds great promise for OER. [ABSTRACT FROM AUTHOR]

The development of earth‐abundant and efficient oxygen evolution reaction (OER) electrocatalysts is necessary for green hydrogen production. The preparation of efficient OER electrocatalysts requires both the adsorption sites and charge transfer on the catalyst surface to be suitably engineered. Herein, the design of an electrocatalyst is reported with significantly enhanced water oxidation performance via dual‐phase engineering, which displays a high number of adsorption sites and facile charge transfer. More importantly, a simple chemical etching process enables the formation of a highly metallic transition boride phase in conjunction with the transition metal hydroxide phase with abundant adsorption sites available for the intermediates formed in the OER. In addition, computational simulations are carried out to demonstrate the water oxidation mechanism and the real active sites in this engineered material. This research provides a new material design strategy for the preparation of high‐performance OER electrocatalysts. [ABSTRACT FROM AUTHOR]

The development of cost effective and high‐performance electrocatalyst is challenging but essential for realizing industrial hydrogen production by electolyzer. Electrocatalysts for water splitting must have active catalytic performance as well as high stability in strong alkaline or acidic media to be used in commercial elecrolyzer. Transition metal based electrocatalysts are considered as highly promising candidates due to their excellent oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performance and stability with low materials cost. Recently, binder free self‐supported electrocatalysts based on transition metals have emerged as state‐of‐the‐art catalytic electrodes due to their high activity and robustness. These properties are attributed to lack of catalyst powder aggregation and a strong synergetic effect between the electrode surface and catalyst. In this mini review, recent development in self‐supported electrocatalysts for OER, HER and also bifunctional OER & HER are reviewed in terms of superior activity and robust stability. Material design strategies, structural and compositional properties, and catalytic performance of recently reported self‐supported electrocatalysts are summarized. Finally, overview of recent studies, challenges and prospects related to self‐supported electrocatalysts are discussed. [ABSTRACT FROM AUTHOR]

Transition metal doping and structural modification of MWCNT via PLA process show the significant enhancement of OER properties. [Display omitted] • The pulsed laser ablation process can effectively incorporate transition metal. • The partially collapsed MWCNT enhanced active site for electrocatalysts. • Ni-doped MWCNTs presented excellent electrocatalysts properties. Transition–metal-doped carbon-based electrocatalysts have attracted attention as alternatives to noble metal electrocatalysts (e.g. IrO 2 and RuO 2) for oxygen evolution reaction (OER) because they are inexpensive and highly efficient. However, their poor catalytic activity and time-consuming synthesis remain a challenge. Herein, we report a facile and green technique using pulsed laser ablation for preparing Ni-doped multi-walled carbon nanotubes (Ni-MWCNTs) as OER catalysts. Ni-MWCNTs exhibit high surface area, oxygen-rich functional groups (e.g., hydroxyl and carboxyl), and successful doping of Ni in the carbon framework. The as-prepared Ni-MWCNTs exhibited excellent OER catalytic performance, with an overpotential of 320 mV at the current density of 10 mA cm−2 in an alkaline medium, which is lower than that of the commercial RuO 2 catalyst. Furthermore, Ni-MWCNTs displayed the initial electrocatalytic activity after 10-h stability tests, demonstrating good electrochemical durability. We believe that this work provides a simple protocol for fabricating heteroatom-doped carbon nanotubes as high-performance OER electrocatalysts. [ABSTRACT FROM AUTHOR]

High-performance oxygen evolution reaction (OER) electrocatalysts are needed to produce hydrogen for energy generation through a carbon-free route. In this work, the solution combustion synthesis (SCS) method was employed to synthesize mixed phases of Co- and Mn-based oxides, and the relationships between the crystalline structure and the catalytic properties in the mixed phases were established. The mixed phases of Co- and Mn-based oxides shows promising OER properties, such as acceptable overpotential (450 mV for 10 mA∙cm−2) and Tafel slope (35.8 mV∙dec−1), highlighting the use of the mixed phases of Co- and Mn-based oxides as a new efficient catalysts for water splitting. Electronic structure of the mixed phases of Co- and Mn based oxides is studied in detail to give insight for the origin of high catalytic activities. In addition, excellent long-term stability for OER in alkaline media is achieved for the mixed phase of Co- and Mn based oxides. [ABSTRACT FROM AUTHOR]

In article number 1803799, Heechae Choi, Yong‐Chae Chung, Taeseup Song and co‐workers report that an electronically double‐layered structure in quaternary metal‐metalloid hollow nanoprism can substantially enhance water oxidation activity as well as the stability of metalmetalloids in alkaline media. Double‐layered vanadium enhances charge transfer at the surface as well as the carrier concentration at the Fermi level. Furthermore, it can also prevent the surrounding metal atoms from leaching out and, as a result, substantially improves electrocatalytic stability of quaternary metal‐metalloid compounds for water oxidation in an alkaline medium. [ABSTRACT FROM AUTHOR]

Nanohybrid consisted of Mo-doped Ni sulfdie and Ni-Fe double layered hydroxide were developed for seawater oxidation showing high catalytic activity, stability, and corrosion resistance. [Display omitted] • Mo-doped Ni sulfdie and Ni-Fe double layered hydroxide were synthesized for seawater oxidation. • (Ni,Mo)S 2 //NF-LDH 300 showed high catalytic activity, stability, and corrosion resistance. • Sulfide layers could unfavor adsorptions of chlrodie at the surface. • 97% selectivity makes it one of the most efficient catalysts for seawater oxidation. Direct seawater electrolysis is of great significance to produce green hydrogen using sustainable resources which can be applicable for water-scarce regions. Herein, a nanohybrid consisted of transition metal sulfide and layered double hydroxide is designed with aims to modify unfavorable surface electronic state of nickel–iron LDH (NF-LDH) for seawater oxidation. Specifically, Mo-doped NiS 2 is deposited onto the self-standing two dimentional NF-LDH nanosheets, (Ni,Mo)S2//NF-LDH 300, using an e-beam evaporator. Physical deposition technique. The designed (Ni, Mo)S 2 //NF-LDH 300 catalyst proves a superior catalytic activity and stability for seawater oxidation under alkaline electrolyte. The deposited transition sulfide layer induces an improved charge transfer as well as reaction kinetics for the (Ni, Mo)S 2 //NF-LDH 300. Further, adsorptions of chloride anions at the surface is substantially suppressed due to the deposited transition metal sulfide effectively preventing chloride corrosions. The (Ni, Mo)S 2 //NF-LDH 300 demonstrates practical level of performance for alkaline seawater oxidation, shedding lights on our catalyst design strategy for direct seawater electrolysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • HER and ORR electrocatalyst derived from Ni MOF was synthesized. • N-doped carbon layer was implemented to protect the HER catalyst. • ORR catalytic carbon layer coating increases HER stability. • The proposed method can enhance the stability of various Ni-based catalysts. Alkaline electrolysis is one of the most powerful technologies to produce hydrogen energy, where the electrocatalysts play an important role. The cathode electrocatalysts often suffer from undesirable oxidation due to the oxygen gas crossover through the porous separator during electrolysis. This leads to oxygen reduction reaction (ORR) on the cathode electrocatalysts, resulting in the loss of activity for hydrogen evolution reaction (HER). Here, we report a highly efficient and durable HER and ORR bifunctional electrocatalyst derived from Ni metal-organic frameworks to address the above problem. Decoupled active sites for ORR and HER are induced in a hybrid material, NiFeP@Ni_NC, where an ORR catalytic N-doped nanocarbon layer can protect a HER catalytic Niδ+ from the undesired ORR. Therefore, excellent bifunctional stability is secured for NiFeP@Ni_NC. The strategy to enhance HER stability presented herein can be widely extended to design bifunctional electrocatalysts with improved stability in alkaline electrolysis. [ABSTRACT FROM AUTHOR]