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Aluminum‐air battery (AAB) with alkaline‐based aqueous electrolyte have attracted intensive research interests due to high‐capacity density, low cost, and high safety. However, severe hydrogen evolution reaction (HER) of Al anode in alkaline electrolyte extremely restricts its large‐scale application. In this work, ZnO with a group of quaternary ammonium salts (QAS, denoted as C1, C2, C4, C6, and C8 depending on the length of non‐polar group) are introduced into electrolytes to inhibit HER. It is revealing that capacity density initially increases with C1, C2, or C4, up to 2564 mAh gAl−1 with anodic utilization rate of 86.0%, and then follows by a decline (C6 and C8). The addition of QAS creates "physical‐hydrophobic interface" by non‐polar group owing to its electrophilic property and constructs "chemical‐hydrophobic interface" with polar group by reducing water activity. QAS also promotes the uniform growth of Zn‐based film, as a barrier against H2O. Thus, HER is effectively inhibited to improve the capacity density. With further increasing non‐polar group length (C6 or C8), the bonding status of the film deteriorates with enhanced H2O activity, leading to the recurrence of HER. This work explores the effect of non‐polar groups on inhibiting HER and opens the door to stable anodes for alkaline‐based batteries. [ABSTRACT FROM AUTHOR]

Noble metal Pt‐based catalysts have slow water dissociation kinetics at high pH conditions, making it difficult for water molecules to be electrochemically activated. Utilizing ligand effect and strain effect to tailor catalytic active sites is a common method, while the understanding of mechanism of their interaction remains obscure due to the complexity of the process. This study proposes a pulse‐induced torsional strained PtRu mesocrystals (PtRu MCs) with 20 times higher mass activity than commercial Pt/C. The combination of experimental results and theoretical calculations reveals that the ligand effect induced by Ru doping accelerates the kinetics of the water dissociation reaction, while the pulse‐induced torsion strained dominates the thermodynamic optimization of the hydrogen adsorption reaction. The structure‐activity relationship defined by the synergistic effect under the complementary advantages of the strain and doping provides guidance for the design of future basic hydrogen evolution catalysts. The catalyst can run stably at 1 A cm−2 for 500 h, showing potential for industrial application. [ABSTRACT FROM AUTHOR]

Atomically precise composite site‐based catalysts with new electrocatalytic synergistic mechanisms and enhanced electrocatalytic activities have emerged as a frontier in the electrocatalysis community. This topical review focuses on the recent research advances of atomically precise metal composite sites‐based electrocatalysts. This work first demonstrates an overview of the configurations of atomically precise composite sites, including a discussion of the advanced methods employed for understanding the composite sites. The review then provides a comprehensive organization of the previously reported methodologies of synthesizing electrocatalysts with atomically precise composite sites. Representative case studies are provided, starting from the simple one‐step pyrolysis strategy to the species‐by‐species multi‐step pyrolysis strategy. Based on the preceding discussions of the catalyst materials, the review further discusses the unique electrocatalysis mechanisms raised by the composite sites, that are different from the routine single species sites. The electrocatalytic systems mainly involve the oxygen reduction reaction, oxygen evolution reaction, hydrogen evolution reaction, nitrogen reduction reaction, and carbon dioxide reduction reaction. The themes of this section include the true active center determination for composite sites and various types of electrocatalytic synergy mechanisms. Finally, critical unanswered questions and remaining challenges, as well as promising underexplored research directions are identified. [ABSTRACT FROM AUTHOR]

Rational design of Pt single‐atom catalysts provides a promising strategy to significantly improve the electrocatalytic activity for hydrogen evolution reaction. In this work, we presented a novel and efficient strategy for utilizing the low electron‐density region of substrate to effectively trap and confine high electron‐density metal atoms. The Pt single‐atom catalyst supported by nickel selenide with rich vacancies was prepared via a hydrothermal‐impregnation stepwise approach. Through experimental testation and DFT theoretical calculation, we confirm that Pt single atoms are well distributed at cationic vacancies of nickel selenide with loading amount of 3.2 wt. %. Moreover, the atomic Pt combined with the high electronegative Se to form Pt−Se bond as a "bridge" between single atoms and substrate for fast electron translation. This novel catalyst shows an extremely low overpotential of 45 mV at 10 mA cm−2 and an excellent stability over 120 h. Furthermore, the nickel selenide supported Pt SACs exhibits long‐term stability for practical application, which maintains a high current density of 390 mA cm−2 over 80 h with a retention of 99 %. This work points a promising direction for designing single atoms catalysts with high catalytic activity and stability for advanced green energy conversion technologies. [ABSTRACT FROM AUTHOR]

MXenes are promising substrates for supported noble metal electrocatalysts. Yet, it is a significant challenge to modulate the metal–support interaction (MSI) for enhancing catalytic performance. Herein, employing a facile HF etching method, the cation vacancy structures in Ti3C2Tx MXenes are controllably tuned, producing nearly vacancy‐free (Ti3C2Tx‐V0), single Ti atom vacancy (Ti3C2Tx‐VS), or Ti vacancy cluster (Ti3C2Tx‐VC) engineered MXenes. Ruthenium atomic clusters, as a model catalyst, successfully anchor on all MXene substrates. Different from the terminal O/F coordination groups on routine Ti3C2Tx MXene surfaces, the Ti vacancy clusters in Ti3C2Tx‐VC create unique lattice carbon ligand environment toward Ru species, which induces ultra‐strong MSI. As a result, compared to Ti3C2Tx‐V0 and Ti3C2Tx‐VS, the Ti3C2Tx‐VC modulated Ru clusters (Ru@Ti3C2Tx‐VC) exhibit the optimized balance of H2O adsorption/dissociation and OH/H desorption, thereby delivering superior electrocatalytic performance in the alkaline hydrogen evolution reaction (HER). Within the wide range from laboratory‐level (90 mA cm−2) to industrial‐level (1.5 A cm−2) current density, Ru@Ti3C2Tx‐VC outperforms commercial Pt/C in terms of overpotential and mass activity. Moreover, as a universal substrate for noble metal catalysts, Ti3C2Tx‐VC can also anchor Ir/Pt/Rh atomic clusters and enable excellent HER catalytic activity. This work expands the scope of the MSI between MXene and noble metal catalysts. [ABSTRACT FROM AUTHOR]

Alloying platinum with early transition metals is a promising approach to optimize the adsorption behaviors of catalysts. Nevertheless, the large negative redox potential between early transition metals and Pt hinders the fabrication of such alloys. Herein, a strategy combining the thermal shock technique with electrochemical activation to prepare Pt3V alloy as a hydrogen evolution reaction catalyst is reported for the first time. Electrochemical tests show that the as‐prepared catalyst exhibits exceptional catalytic activity and durability in 0.5 m H2SO4, surpassing the state‐of‐the‐art 20 wt.% Pt/C. The catalyst can maintain its activity after 100 h tests without evident decay under the current density of 500 mA cm−2. Theoretical calculations demonstrate that the optimized hydrogen absorption and high vacancy formation energy of Pt3V contributes to the enhanced electrocatalytic activity and stability. This work may spur future research for other Pt‐based early transition metal alloy catalysts for electrocatalysis. [ABSTRACT FROM AUTHOR]

The state‐of‐the‐art active hydrogen evolution reaction (HER) catalysts in acid electrolytes generally lose considerable catalytic performance in alkaline electrolytes mainly due to the additional water dissociation step. Designing composite materials is an effective strategy to accelerate alkaline water electrolysis by optimizing the electronic structure of materials. Here, different phases of Co(OH)2‐supported Ru clusters (α/β‐Co(OH)2@Ru) are prepared for enabling a highly efficient electrocatalytic HER performance in alkaline solution. The prepared α‐Co(OH)2 nanosheets facilitate the loading of uniform and high‐density Ru clusters and the formed highly active RuOCo bonds at the interface. The synergistic interaction endows the hybrid catalyst with low overpotential of 33 mV at 10 mA cm−2. Moreover, the homemade anion exchange membrane water electrolysis cell based on α‐Co(OH)2@Ru affords a cell voltage of 2 V to drive a current density of 270 mA cm−2 and performs stably during continuous operation for over 100 h. Density functional theory calculations demonstrate that active RuOCo bonds in α‐Co(OH)2@Ru optimize the energy barriers for H2O dissociation and OH− desorption to facilitate the Volmer reaction step. This work offers a strategy for designing interfacial chemical bonds for high electrocatalytic activity. [ABSTRACT FROM AUTHOR]

It is vitally important to develop highly active, robust and low‐cost transition metal‐based electrocatalysts for overall water splitting in neutral solution especially at large current density. In this work, amorphous Mo‐doped NiS0.5Se0.5 nanosheets@crystalline NiS0.5Se0.5 nanorods (Am−Mo−NiS0.5Se0.5) was synthesized using a facil one‐step strategy. In phosphate buffer saline solution, the Am−Mo−NiS0.5Se0.5 shows tiny overpotentials of 48 and 209 mV for hydrogen evolution reaction (HER), 238 and 514 mV for oxygen evolution reaction (OER) at 10 and 1000 mA cm−2, respectively. Moreover, Am−Mo−NiS0.5Se0.5 delivers excellent stability for at least 300 h without obvious degradation. Theoretical calculations revealed that the Ni sites in the defect‐rich amorphous structure of Am−Mo−NiS0.5Se0.5 owns higher electron state density and strengthened the binding energy of H2O, which will optimize H adsorption/desorption energy barriers and reduce the adsorption energy of OER determining step. [ABSTRACT FROM AUTHOR]

The development of cost‐effective and highly efficient electrocatalysts to accelerate distinct electrochemical reactions is essential to help the industry to achieve a low‐carbon footprint. Single‐atom alloys (SAAs) with the characteristics of unique electronic structures, well‐defined active sites, and maximum atom utilization demonstrate promising potential to replace traditional noble metal catalysts. SAAs are expected to tailor the adsorption properties of reaction species, thus promoting electrocatalytic behaviors. Herein, representative synthetic strategies including wet chemistry, galvanic replacement, dealloying, and atomic layer deposition are introduced, followed by a summary of applications of SAAs in hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, carbon dioxide reduction reaction, and ethanol electro‐oxidation to provide an in‐depth understanding of the structure–activity relationship. Moreover, the challenges and perspectives in this emerging field of SAAs are discussed. [ABSTRACT FROM AUTHOR]

Facilitating the cleavage of a NN bond and suppressing the competition hydrogen evolution reaction is essential, and but still remains a challenge in nitrogen reduction reaction (NRR). Crystal phase tailoring is an effective approach to optimize the energy barrier during the NRR process to improve the catalytic efficiency. Herein, a boron‐doping strategy to induce phase transfer from hexagonal Mo2C to cubic Mo2C for regulating the electronic structure and catalytic properties of electrocatalysts toward NRR is reported. The B doped cubic Mo2C is found to increase the exposure of active sites, regulate the d band center of Mo for enhancing the adsorption and activation of nitrogen, and reduce the energy barrier of NRR pathway, giving rise to a high ammonia yield of 52.1 μg h−1 mg−1 at −0.6 V versus reversible hydrogen electrode under ambient conditions. More importantly, the hydrogen adsorption on the surface of electrocatalyst is significantly inhibited due to the B‐doping, further improving the faradic efficiency to 36.9%, which is 4 times that of hexagonal Mo2C (9%). This work not only sheds light on the atomic‐scale design of efficient NRR electrocatalysts, but also provides a promising avenue for synchronizing the catalytic activity and selectivity for catalytic reactions. [ABSTRACT FROM AUTHOR]

Rational design of bifunctional efficient electrocatalysts for both oxygen reduction (ORR) and oxygen evolution reactions (OER) is desirable—while highly challenging—for development of rechargeable metal–air batteries. Herein, an efficient bifunctional electrocatalyst is designed and fabricated by encapsulating Co nanoparticles in interconnected N‐doped hollow porous carbon nanofibers (designated as Co@N‐C/PCNF) using an ultrafast high‐temperature shock technology. Benefiting from the synergistic effect and intrinsic activity of the CoNC moiety, as well as porous structure of carbon nanofibers, the Co@N‐C/PCNF composite shows high bifunctional electrocatalytic activities for both OER (289 mV at 10 mA cm−2) and ORR (half‐wave potential of 0.85 V). The CoNC moiety in the composite can modulate the local environmental and electrical structure of the catalysts, thus optimizing the adsorption/desorption kinetics and decreasing the reaction barriers for promoting the reversible oxygen electrocatalysis. Co@N‐C/PCNF‐based aqueous Zn–air batteries (AZAB) provide high power density of 292 mW cm−2, and the assembled flexible ZAB can power wearable devices. [ABSTRACT FROM AUTHOR]

Tuning the electronic states near the Fermi level can effectively facilitate the reaction kinetics. However, elucidating the role of a specific electronic state of metal oxide in simultaneously regulating the CO2 electroreduction reaction (CO2RR) and competing hydrogen evolution reaction (HER) is still rare, making it difficult to accurately predict the practical CO2RR performance. Herein, replacing the Zn site by heteroatoms with different outer electrons (Mo and Cu) is found to tune both occupied and unoccupied orbitals near the Fermi level of ZnO. Moreover, the different electronic states significantly modulate both CO2RR and HER activity with a totally inverse trend, thus dramatically tuning the practical CO2RR performance. In parallel, the correlation between electronic states, reaction free energies and practical activity is demonstrated. This work provides a possibility for engineering efficient CO2RR eletrocatalysts through tunable composition and electronic structures. [ABSTRACT FROM AUTHOR]