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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]

Hydrogen evolution reaction and dendrite growth seriously break the Zn plating/stripping process at the electrolyte/electrode interface, causing the instability of the Zn anode of aqueous zinc ion batteries. To improve the Zn anode stability and reversibility, we report a new electrolyte additive of aqueous electrolyte with the hydrophobic group. This interfacial hydrophobicity maximises the exclusion of free water from the Zn anode surface, which blocks water erosion and reduces interfacial side reactions. Thus, in an optimal 2 M ZnSO4 electrolyte with 2 g·L−1 Tween-85, the hydrogen evolution reaction and other water-induced undesired reactions can be suppressed, which greatly improves the cycling stability and Coulombic efficiency (CE) of Zn plating/stripping process. The stable cycle time of the Zn//Zn symmetric battery reaches over 1300 h, especially at a high current density and a high areal capacity (more than 650 h at 5 mA·cm−2, 5 mAh·cm−2). The average Coulomb efficiency (CE) of Zn//Ti asymmetric cell achieves 98.11% after 300 cycles. The capacity retention rate of Zn//MnO2 full battery is up to 88.6% after 1000 cycles. [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]

Here, we report the synthesis of activated NiCo LDH to immobilize Pt, Ir and Rh single atoms for hydrogen evolution reaction. The Pt/A-NiCo LDH electrocatalyst exhibits the highest catalytic ability with a low overpotential of 16 mV to achieve a current density of 10 mA cm−2 and a mass activity about 24.8-fold that of commercial Pt/C. The results suggest that the Pt single atom catalyst can not only accelerate the Volmer steps in alkaline media, but also optimize the hydrogen adsorption process, improving the HER catalytic activity. [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]

Purpose: This paper aims to study the effect of temperature on the process and kinetic parameters of the hydrogen evolution reaction of X80 under cathodic protection (CP) in 3.5% NaCl solution. Design/methodology/approach: Potentiodynamic polarization combined with the hydrogen permeation test is used to analyze the hydrogen evolution reaction (HER) process and the rate-determining step for which is diagnosed through the electrochemical impedance spectrum method. Then, the influence of temperature on kinetic parameters of HER can be known from the results obtained by using the Iver-Pickering-Zamenzadeh model for data analysis. Findings: The results show that the HER proceeds through Volmer–Tafel route with the Volmer reaction acting as the rate-controlling step; Increasing temperature gives a higher activity of the HER on X80, it also accelerates the hydrogen desorption and diffusion of hydrogen into the metal. Originality/value: There exist few studies on the topic of how temperature affects the HER process. It is imperative to conduct a relevant study to give some instruction in cathodic protection system design and this paper fulfills this need. [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]

This paper introduces HER activity of a string of Ni-P nanoparticles. The hydrogen evolution reaction (HER) activity of different Ni-P nanoparticles hinges on elemental ratios of nickel to phosphorus and nickel phosphide phases through annealing processes, which lead to utter diverse HER performances in HSO and NaOH. The sample annealed under 350 °C by 4 h, mainly comprised by NiP and NiP, shows overpotential of 333 mV to achieve 100 mA·cm (η = 333 mV) current density in acidic condition, whereas in alkaline condition, the non-heat-treated sample, mainly formed by NiP and NiP, shows the best HER performance. Ni-P nanoparticles have also displayed distinguished durability in both HSO and NaOH. The superior HER activity and durability are supported by a series of characterizations and stem from Ni-P nanoparticles' nature, including their morphology, good ensemble effect between nickel and phosphorus, and anti-corrosive quality. [ABSTRACT FROM AUTHOR]

Highlights: Nanomaterials-based nickel foam (NF-C/CoS/NiOOH) with nanosheets structure and core–shell heterostructure was prepared for the first time by a facile and fast synthesis strategy of Joule-heating and water soaking treatment. The formation mechanism of nanosheets structure was proposed that the driving force of nanosheets structure generation was the metastable nickel activated by thermal shock, and the CoS could induce the NiOOH nanosheets growing continually. NF-C/CoS/NiOOH exhibited good oxygen evolution, hydrogen evolution, and overall water splitting performance. Nanomaterials based on nickel foam (NF) have been widely applied in energy conversion and storage field. Traditional synthesis methods such as hydrothermal method which is dangerous and high cost limited the scalable developments. Herein, we report a fast, simple, and low-cost synthesis method of nanomaterials based on NF by Joule-heating and water soaking treatment. Thin carbon-coated CoS on NF (NF-C/CoS) was synthesized by Joule-heating for a few seconds with rapid cooling. And then, NF-C/CoS/NiOOH with core–shell heterostructure was fabricated by soaking treatment of NF-C/CoS in water on which NiOOH nanosheets grew spontaneously. The formation mechanism is proposed that the coordination complex precursor converts into C/CoS on NF driven by Joule-heating, and the nickel on the surface of NF is activated to form metastable nickel simultaneously. The metastable nickel reacting with water leads to the formation of NiOOH, and the induction of CoS makes NiOOH grow continuously. This synthesis technology provides a new route to manufacture NF-based nanostructures, and the as-fabricated NF-C/CoS/NiOOH exhibits great potential as electrocatalyst for oxygen evolution reaction and hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

The unique electronic structure and diverse elemental composition of high-entropy materials (HEMs) have already showcased remarkable properties in the realm of oxygen evolution reaction (OER). Despite this, the active sites and reaction pathways of HEMs have yet to be fully understood. Our findings indicate that the addition of Fe in HEMs results in a more positive valence state of metals, leading to the enhancement of the covalent characteristic of the M-O bond. Additionally, the predominant oxygen 2p orbitals near the Fermi level enables lattice oxygen to function as an OER center. Guided by theoretical calculations, we synthesized a nanoporous NiFeCoMnOOH (np-NiFeCoMnOOH) electrocatalyst exhibited a low overpotential of 194 mV at 10 mA cm−2 and long-term stability of 120 h at 100 mA cm−2. These results offer insights into the reaction mechanisms of HEM electrocatalysts and may guide future studies in designing high-entropy electrocatalysts with superior activity. Theoretical calculations guided the synthesis of np-NiFeCoMnOOH free-standing composite electrodes exhibiting strong LOM pathway selectivity in the OER process and scrutinizes the reaction pathway transition mechanism, which from AEM to LOM, and the source of excellent OER activity. [Display omitted] • Calculations validate the possibility and causes of pathway transformations of high-entropy OER catalysts. • Multiple active sites and two reaction pathways have been investigated. • np-NiFeCoMnOOH electrode exhibits a low overpotential of 194 mV at 10 mA cm−2 and long-term stability of 120 h at 100 mA cm−2. [ABSTRACT FROM AUTHOR]

Graphical abstract A typical core-shell Cu 7 S 4 -coated Cu 2 O nanocubes (NCs) was designed to enhance the hydrogen evolution under solar light irradiation by water splitting. The presence of Cu 7 S 4 can enlarge light harvesting, promote the electron transfer, prolong the hole lifetime, and suppress electron-hole pairs recombination, and thus photoresponse density and solar conversion efficiency improved. Moreover, Cu 2 O/Cu 7 S 4 NCs display considerable hydrogen production rate of 1689.00 μmol g−1 h−1 under full-spectra irradiation with additives of Na 2 SO 3. Highlights • Cu 7 S 4 as a cocatalyst formed on the surface of Cu 2 O cubes in situ and firstly applied to photocatalytic hydrogen evolution. • The formation of the thin layer Cu 7 S 4 extends the light harvesting and electron-hole pairs spartion of Cu 2 O. • Internal electric field (IEF) can accelerate the photo-generated electron transfer and enhance the HER over Cu 2 O nanocubes by heterojunction. • The hydrogen production rate of Cu 2 O/Cu 7 S 4 NCs was reached to 1689.00 μmolg-1h-1 under visible light irradiation with additive of Na 2 SO 3. Abstract P-type Cu 2 O is an advantageous photocatalyst as the appropriate bandgap structure and low-cost. However, poor photocatalytic and instability of such promising material is still a great challenge. Here the core-shell Cu 7 S 4 -coated Cu 2 O nanocubes (Cu 2 O/Cu 7 S 4 NCs) were successfully synthesized by solution method coupled with anion exchange, and were firstly employed to hydrogen evolution reaction (HER). The resultant integrated structure of Cu 2 O/Cu 7 S 4 NCs exhibited apparent improved photocatalytic hydrogen evolution activity compared with Cu 2 O photocatalyst. Particularly, Cu 2 O/Cu 7 S 4 NCs had a high hydrogen production rate of 1689.00 μmol g−1 h−1 under full spectra irradiation with additive of Na 2 SO 3 , which was higher than that of Cu 2 O NCs with a factor of 1.71 times. Excellent synergistic effect of Cu 2 O and Cu 7 S 4 can be responsible for the improved hydrogen evolution properties, namely, the presence of Cu 7 S 4 with localized surface plasma resonance (LSPR) can promote the photogenerated electrons transfer from the Cu 2 O surface, prolong the photogenerated holes lifetime, accelerate the separation of photogenerated electrons and holes, and ameliorate the photoelectric properties of semiconductors. The in situ formed multifunctional Cu 7 S 4 layer offers a promising avenue to design photocathodes rationally for photocatalytic water reduction. [ABSTRACT FROM AUTHOR]

Abstract One-dimensional transition metal phosphides with large specific surface areas and efficient conductivity have the great potential in both hydrogen and oxygen evolution reaction (HER and OER) as bifunctional catalysts, which are at the heart of water splitting. Herein, we firstly report the controllable synthesis of Co 2 P nanorods through a substrate- and template-free facile phosphating reaction. Electrochemical test results reveal that the synthesized Co 2 P nanorods exhibit superior bifunctional activity with overpotentials of 87 mV for HER and 310 mV for OER at 10 mA cm−2, respectively, relative to Co 2 P/CoP branched nanostructure, CoP nanoparticles and commercial Co 2 P in alkaline media. In addition, the bifunctional Co 2 P nanorods catalysts enable overall water splitting with a cell voltage of 1.65 V to achieve 10 mA cm−2 and stabilized potentials at different current densities testing over 24 h. Further analysis demonstrate that the remarkably bifunctional activity is contributed to high charge transfer efficiency, large contact area with electrolyte and a large number of exposed active sites provided by the rod-like nanostructure. This work should shed light on an industrialized pathway for the future design of phosphide catalysts to apply to overall water splitting even other emerging energy devices. Graphical abstract Image 1 Highlights • Co 2 P nanorods with the diameter and length of around 200 nm and 10–20 nm. • Firstly prepared via a substrate- and template-free facile phosphating reaction. • With the increase in active area and the minimum in charge transfer resistance. • Displaying superior bifunctional activity and stability for water splitting. • Paving the way to in large scale obtain highly active and durable TMPs. [ABSTRACT FROM AUTHOR]

Nickel phosphide has been shown to be active toward hydrogen evolution reaction (HER). In this paper, we demonstrate the phase and composition controllable synthesis of nickel phosphide-based nanoparticles (Ni P-based NPs) via a low-temperature phosphidation reaction (250 °C) using NaH 2 PO 2 as the phosphorus source and the as-prepared Ni(OH) 2 precursor as the nickel source. Interestingly, by changing the NaOH concentration and nickel source used to fabricate Ni(OH) 2 precursors, we could adjust the phases and compositions of as-synthesized Ni P-based nanocatalysts from Ni 5 P 4 , Ni 2 P to Ni 12 P 5 . The different steric hindrance and the electrostatic repulsion of synthesized β-Ni(OH) 2 precursors result in the formation of three Ni P phases with various Ni:P ratios. Electrochemical characterizations reveal that the Ni P-based NPs with P-rich phase (Ni 5 P 4 +Ni 2 P) exhibit remarkable electrocatalytic HER property, with low overpotential ( η ) of 111 mV to reach a current density of 10 mA cm −2 in a 0.5 M H 2 SO 4 media, which is superior than those of pure Ni 2 P ( η = 118 mV) and the Ni-rich Ni P-based counterpart (Ni 12 P 5 +Ni 2 P) ( η = 131 mV). This is attributed to the stronger ensemble effect of P and more active sites provided by P-rich Ni P-based NPs. Our results demonstrate that by tailoring the surface properties of Ni(OH) 2 precursors, the phases and compositions of Ni P-based nanoparticles could be easily tuned, which provides a simple, economic, and green strategy to optimize the HER performance of transition metal phosphide-based electrocatalysts. [ABSTRACT FROM AUTHOR]

Catalyst has been a bottleneck in hydrogen evolution reaction (HER) – a half reaction of water splitting. Hitherto the most efficient HER catalyst in terms of catalytic capacity remains to be those platinum group metals, especially platinum; however, rare metals' exorbitant cost and scarcity inhibit their further application in industry, which therefore call for catalysts prepared from earth-abundant elements. Herein, we introduce nickel phosphide nanospheres (NPNs) bearing excellent HER activity. Prepared via a facile, inexpensive, and eco-friendly preparation procedure, the as-synthesized NPNs have perfect over-potential to reach −100 mA/cm 2 (η 100 ), with η 100 reaching 251 mV in 0.5 M H 2 SO 4 . A series of durability tests, including cyclic voltammetry (CV) and chronoamperometry, also indicate NPNs' favorable stability under both acidic and alkaline conditions. After taking account of a string of factors, including NPNs' mass density, handy preparation process, superior catalytic activity as well as favorable durability, the NPNs bear probable potentiality of taking traditional noble metals' place as the HER catalyst and are worth studying further. [ABSTRACT FROM AUTHOR]

Metallic nanomaterials with multidimensional defects are promising for electrocatalysis, whereas exploring facile approaches to synthesize such materials with peculiar structure remains challenging. Here, we firstly synthesized Ru nanoparticles with abundant stacking faults (SFs) combining ultrafast heating with rapid quenching. The close-packed planes of perfect hexagonal closed-packed partially transform into face-centered cubic in the SFs region. It requires 196 mV and 35 mV to drive hydrogen evolution reaction and oxygen evolution reaction under 10 mA/cm2 current density, prominently expedites overall water splitting with 1.51 V in acid. Theoretical calculations demonstrate the performance is originated from synergistic effect of the SFs and induced continuous strain field, among which the dominant compressive strain attenuates crystal field splitting effect of Ru sites, thus enhancing the electron transfer of Ru sites. The excellent inter-orbital p-d transfers determine strong electronic activities for boosting OER performance. This work provides insights for rational design of catalysts with defective structures. [Display omitted] • SF-Ru NPs were prepared by a non-equilibrium ultrafast synthesis strategy (sub 1 s). • It requires 196 and 35 mV to reach current density of 10 mA/cm2 for OER and HER. • Compressive strain dominated field adjusts the center of d-band to optimal position. • Synergistic effect between stacking faults and strain field leads to the performance. [ABSTRACT FROM AUTHOR]