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The design of high‐entropy single‐atom catalysts (HESAC) with 5.2 times higher entropy compared to single‐atom catalysts (SAC) is proposed, by using four different metals (FeCoNiRu‐HESAC) for oxygen reduction reaction (ORR). Fe active sites with intermetallic distances of 6.1 Å exhibit a low ORR overpotential of 0.44 V, which originates from weakening the adsorption of OH intermediates. Based on density functional theory (DFT) findings, the FeCoNiRu‐HESAC with a nitrogen‐doped sample were synthesized. The atomic structures are confirmed with X‐ray photoelectron spectroscopy (XPS), X‐ray absorption (XAS), and scanning transmission electron microscopy (STEM). The predicted high catalytic activity is experimentally verified, finding that FeCoNiRu‐HESAC has overpotentials of 0.41 and 0.37 V with Tafel slopes of 101 and 210 mVdec−1 at the current density of 1 mA cm−2 and the kinetic current densities of 8.2 and 5.3 mA cm−2, respectively, in acidic and alkaline electrolytes. These results are comparable with Pt/C. The FeCoNiRu‐HESAC is used for Zinc–air battery applications with an open circuit potential of 1.39 V and power density of 0.16 W cm−2. Therefore, a strategy guided by DFT is provided for the rational design of HESAC which can be replaced with high‐cost Pt catalysts toward ORR and beyond. [ABSTRACT FROM AUTHOR]

Urea oxidation reaction (UOR) has been utilized to substitute the oxygen evolution reaction (OER), to escalate the energy conversion efficiency in electrochemical hydrogen generation processes with denitrification of widespread urea in wastewater. This study reports breakthroughs in Ni‐based UOR electrocatalysts, particularly with NiFe oxalate (O‐NFF), derived from Ni3Fe alloy foam with prismatic nanostructures and elevated surface area. The O‐NFF achieves cutting‐edge performances, representing 500 mA cm−2 of current density at 1.47 V RHE and exceptionally low Tafel slope of 12.1 mV dec−1 (in 1 m KOH with 0.33 m urea). X‐ray photoelectron/absorption spectroscopy (XPS/XAS) coupled with density functional theory calculations unveil that oxalate ligands induce charge deficient Ni center, promoting stable urea‐O adsorption. Furthermore, Fe dopants enhance oxalate‐O charge density and H‐bond strength, facilitating C‐N cleavage for N2 and NO2− formation. The extraordinary UOR kinetics by the tandem effects of oxalate and Fe prevent Ni over‐oxidation, corroborated by operando XAS, minimizing OER interference. It agrees with an adaptive reconstruction to Fe‐doped β‐NiOOH on top surface in extended urea electrolysis with marginal loss in UOR kinetics. This findings shed light to bimetal‐organic‐framework as (pre)catalysts to improve industrial electrolytic H2 production. [ABSTRACT FROM AUTHOR]

To realize economically feasible electrochemical CO2 conversion, achieving a high partial current density for value-added products is particularly vital. However, acceleration of the hydrogen evolution reaction due to cathode flooding in a high-current-density region makes this challenging. Herein, we find that partially ligand-derived Ag nanoparticles (Ag-NPs) could prevent electrolyte flooding while maintaining catalytic activity for CO2 electroreduction. This results in a high Faradaic efficiency for CO (>90%) and high partial current density (298.39 mA cm‒2), even under harsh stability test conditions (3.4 V). The suppressed splitting/detachment of Ag particles, due to the lipid ligand, enhance the uniform hydrophobicity retention of the Ag-NP electrode at high cathodic overpotentials and prevent flooding and current fluctuations. The mass transfer of gaseous CO2 is maintained in the catalytic region of several hundred nanometers, with the smooth formation of a triple phase boundary, which facilitate the occurrence of CO2RR instead of HER. We analyze catalyst degradation and cathode flooding during CO2 electrolysis through identical-location transmission electron microscopy and operando synchrotron-based X-ray computed tomography. This study develops an efficient strategy for designing active and durable electrocatalysts for CO2 electrolysis. A key factor for the electrochemical reduction of CO2 to CO is limiting the competing H2 evolution reaction. Here, authors use real-time synchrotron X-ray computed tomography to show that a silver nanoparticle-ligand catalyst structure improves water management, thereby maintaining CO production. [ABSTRACT FROM AUTHOR]

Although great efforts on the delicate construction of a built‐in electric field (BIEF) to modify the electronic properties of active sites have been conducted, the substantial impact of BIEF coupled with electrode potential on the electrochemical reactions has not been clearly investigated. Herein, we designed an alkaline hydrogen evolution reaction (HER) catalyst composed of heterogeneous Ru−CoP urchin arrays on carbon cloth (Ru−CoP/CC) with a strong BIEF with the guidance of density functional theory (DFT) calculations. Impressively, despite its unsatisfactory activity at 10 mA cm−2 (overpotential of 44 mV), Ru−CoP/CC exhibited better activity (357 mV) than the benchmark Pt/C catalyst (505 mV) at 1 A cm−2. Experimental and theoretical studies revealed that strong hydrogen adsorption on the interfacial Ru atoms created a high energy barrier for hydrogen desorption and spillover, resulting in unsatisfactory activity at low current densities. However, as the electrode potential became more negative (i.e. the current density increased), the barrier for hydrogen spillover from the interfacial Ru to the Co site, which had near‐zero hydrogen adsorption energy, significantly decreased, thus greatly accelerating the whole alkaline HER process. This explains why the activity of Ru−CoP is relatively susceptible to the electrode potential compared to Pt/C. [ABSTRACT FROM AUTHOR]

Even though grain boundaries (GBs) have been previously employed to increase the number of active catalytic sites or tune the binding energies of reaction intermediates for promoting electrocatalytic reactions, the effect of GBs on the tailoring of the local chemical environment on the catalyst surface has not been clarified thus far. In this study, a GBs‐enriched iridium (GB−Ir) was synthesized and examined for the alkaline hydrogen evolution reaction (HER). Operando Raman spectroscopy and density functional theory (DFT) calculations revealed that a local acid‐like environment with H3O+ intermediates was created in the GBs region owing to the electron‐enriched surface Ir atoms at the GBs. The H3O+ intermediates lowered the energy barrier for water dissociation and provided enough hydrogen proton to promote the generation of hydrogen spillover from the sites at the GBs to the sites away from the GBs, thus synergistically enhancing the hydrogen evolution activity. Notably, the GB−Ir catalyst exhibited a high alkaline HER activity (10 mV @ 10 mA cm−2, 20 mV dec−1). We believe that our findings will promote further research on GBs and the surface science of electrochemical reactions. [ABSTRACT FROM AUTHOR]

Simultaneous optimization of the energy level of water dissociation, hydrogen and hydroxide desorption is the key to achieving fast kinetics for the alkaline hydrogen evolution reaction (HER). Herein, the well‐dispersed Ru clusters on the surface of amorphous/crystalline CeO2‐δ (Ru/ac‐CeO2‐δ) is demonstrated to be an excellent electrocatalyst for significantly boosting the alkaline HER kinetics owing to the presence of unique oxygen vacancy (VO) and Ru Lewis acid–base pairs (LABPs). The representative Ru/ac‐CeO2‐δ exhibits an outstanding mass activity of 7180 mA mgRu−1 that is approximately 9 times higher than that of commercial Pt/C at the potential of −0.1 V (V vs RHE) and an extremely low overpotential of 21.2 mV at a geometric current density of 10 mA cm−2. Experimental and theoretical studies reveal that the VO as Lewis acid sites facilitate the adsorption of H2O and cleavage of H‐OH bonds, meanwhile, the weak Lewis basic Ru clusters favor for the hydrogen desorption. Importantly, the desorption of OH from VO sites is accelerated via a water‐assisted proton exchange pathway, and thus boost the kinetics of alkaline HER. This study sheds new light on the design of high‐efficiency electrocatalysts with LABPs for the enhanced alkaline HER. [ABSTRACT FROM AUTHOR]

[Display omitted] • P-doped graphene quantum dots were synthesized with different P-C bond configurations via simple hydrothermal process. • The PGQD3/GH composite demonstrated excellent photocatalytic hydrogen production of 20.47 mmol·g−1·h−1 in seawater splitting. • The PGQD3/GH composite performs superior bifunctional electrochemical activities of HER and OER. • The seawater electrolysis cell using PGQD3/GH composite delivers small overall voltage with excellent stability. Designing metal-free catalyst with outstanding activity for both photocatalytic and electrocatalytic seawater splitting is highly demand and still remained challenge. This work demonstrates the synthesis of P-doped graphene quantum dots (PGQDs) containing different P-configuration bonding of PC 3 , PO 4 and PO 3 via synthesis temperature controlled simple hydrothermal process. Specifically, PGQDs having PC 3 -bonds (PGQD3) shows effectively tunable electronic structure, significant enhancing visible light absorption, then their hybrid composite with graphene hydrogel (PGQD3/GH) is prepared. The PGQD3/GH composite possesses excellent photocatalytic hydrogen production with yield of 20.47 mmol·g−1·h−1 in seawater splitting. Furthermore, the PGQD3/GH composite performs superior electrochemical activities of hydrogen evolution reaction (HER) toward seawater with an overpontetial of 41 mV at 10 mA·cm−2 as well as oxygen evolution reaction (OER) with 262 mV at 10 mA·cm−2. In seawater electrolysis cell, the PGQD3/GH composite delivers small overall voltage of 1.62 V to obtain high current density of 500 mA·cm−2 with excellent stability for 1000 h continuous operation, outperforming the commercial Pt/C and IrO 2. This work demonstrates the role of PC 3 -bond in modulating the band gap and active site for photocatalytic and electrocatalytic seawater splitting reaction that may provide new idea for developing porous non-metal all-carbon catalyst for seawater splitting by both photocatalysis and electrocatalysis. [ABSTRACT FROM AUTHOR]

Doped carbon structures have been developed as non-precious metal catalysts for oxygen reduction reactions (ORR) in polymer electrolyte membrane fuel cells (PEMFCs). Among doped carbon structures, Fe- and N-doped carbon (Fe/N/C) nanostructured catalysts have received attention due to their catalytic activity, comparable to that of Pt, avoiding the use of critical raw materials. However, obviously, its durability is not yet neither fully understood nor comparable to that of traditional catalysts. In this study, we synthesized mesoporous F-doped Fe/N/C, which is a tri-doped carbon nanostructure, as a cathode catalyst for ORR. Tri-doped carbon catalysts with different amounts (x) of F (Fx-Fe/N/C) were prepared using Fe-5,10,15,20-tetrakis(4-methoxyphenyl)-21H,23H-porphine iron(III) chloride and NH 4 F as the Fe/N- and F- doping sources, respectively, and Santa Barbara amorphous-15 as the template. Fx-Fe/N/C with an optimal F content exhibited excellent electrocatalytic performance for ORRs i.e. a high half-wave potential of 809 mV in 0.1 M HClO 4 solution, a maximum power density of 280 mW cm−2, and a high stability for 4000 min at 0.5 V, owing to the high proportion of FeN x and pyridinic N as active sites, strong C–F bonds, and hydrophobic surfaces. We synthesized mesoporous F-doped Fe/N/C, which is a tri-doped carbon nanostructure, as a cathode catalyst for ORR. Fx-Fe/N/C with an optimal F content exhibited excellent electrocatalytic activity and durability for ORRs owing to the high proportion of FeNx and pyridinic N as active sites, strong C–F bonds, and hydrophobic surfaces. [Display omitted] [ABSTRACT FROM AUTHOR]