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Although layered double hydroxides (LDHs) are extensively investigated for oxygen electrocatalysis, their development is hampered by their limited active sites and sluggish reaction kinetics. Here, sulfur mismatch substitution of NiFe–LDH (S–LDH) is demonstrated, which are in‐situ deposited on nitrogen‐doped graphene (S–LDH/NG). This atomic‐level sulfur incorporation leads to the construction of the tailored topological microstructure and the modulated electronic structure for the improved catalytic activity and durability of bifunctional electrocatalysts. The combined computational and experimental results clarify that the electron transfer between the sulfur anion and Fe3+ generates the high‐valence Fe4+ species, while the mismatch substitution of the sulfur anion induces the metallic conductivity, an increased carrier density, and the reduced reaction barrier. Consequently, the as‐fabricated Zn–air battery achieves a high power density of 165 mW cm‐2, a large energy density of 772 Wh kgZn‐1 at 5 mA cm‐2, and long cycle stability for 120 h, demonstrating its real‐life operation. [ABSTRACT FROM AUTHOR]

The development of efficient electrocatalysts for the CO2 reduction reaction (CO2RR) remains a challenge. Demonstrated here is a NiSn atomic‐pair electrocatalyst (NiSn‐APC) on a hierarchical integrated electrode, which exhibits a synergistic effect in simultaneously promoting the activity and selectivity of the CO2RR to formate. The NiSn atomic pair consists of adjacent Ni and Sn, each coordinated with four nitrogen atoms (N4‐Ni‐Sn‐N4). The as‐prepared NiSn‐APC displays exceptional activity for the CO2RR to formate with a turnover frequency of 4752 h−1, a formate productivity of 36.7 mol h−1 gSn−1 and an utilization degree of active sites (57.9 %), which are superior to previously reported single‐atomic catalysts. Both experimental data and density‐functional theory calculations verify the electron redistribution of Sn imposed by adjacent Ni, which reduces the energy barrier of the *OCHO intermediate and makes this potential‐determining step thermodynamically spontaneous. This synergistic catalysis provides a successful paradigm for rational design and preparation of atomic‐pair electrocatalysts with enhanced performance. [ABSTRACT FROM AUTHOR]

The development of active and inexpensive electrocatalysts for the oxygen evolution reaction (OER) to promote water splitting has always been a major challenge. Cobalt‐based oxides and sulfides have been actively investigated due to their low cost and high activity. However, the lower intrinsic conductivity of cobalt oxide and the inferior stability of cobalt sulfides still limit their practical application. Herein, CoO was chosen for a proof‐of‐concept study in which the anion‐doping strategy was used to obtain an excellent catalyst. Sulfur incorporation optimizes the charge‐transfer properties and active sites of sulfur‐doped CoO (S‐CoO) and thus gives rise to improved catalytic activity. Besides sulfur doping, the stable framework of the cobalt oxide was well maintained, and thus high stability of S‐CoO throughout the reaction process was ensured. Nanoflake electrocatalyst: Sulfur‐doped CoO nanoflakes with loosely packed structure were fabricated by reaction of Co3O4 nanosheets with thioacetamide (TAA) which was used as both sulfur source and reducing agent (see figure). Sulfur doping optimizes the charge‐transfer properties and the active sites and thus leads to clearly enhanced catalytic activity in the oxygen evolution reaction. [ABSTRACT FROM AUTHOR]

Observation of novel linear relationship between Δ G OOH and Δ E H suggests Δ E H as a simple descriptor for rational design of HER/ORR bifunctional graphyne materials. [Display omitted] The high cost and relative scarcity of platinum (Pt) restrict large-scale commercialization of fuel cells, which has spurred researchers to develop low-cost alternatives integrating with high hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) catalytic activity. Herein, we performed density functional theory (DFT) calculations to explore the electrocatalytic activity of graphyne nanotubes (GyNTs). Several GyNTs were found to be potential metal-free electrocatalysts, with both HER and ORR activity superior to Pt. Moreover, we revealed a linear relationship between the Gibbs free energy change of O 2 adsorption (Δ G OOH) and binding energy of H adsorption (Δ E H), which could be attributed to the fact that both the C O bond of OOH adsorption and the C H bond of H adsorption are single bonds. Therefore, Δ E H is proposed as a general descriptor for the rational design of bifunctional graphyne materials toward HERs and ORRs. Our findings provide a simple strategy for the rational design of bifunctional materials. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • MOFs-deriver N-doped CoC x /FeCo@C/rGO was synthesized as a catalyst for ORR. • The ORR activity of N-doped CoC x /FeCo@C/rGO was higher than that of the Pt/C. • The OER activity of N-doped CoC x /FeCo@C/rGO was higher than that of the RuO 2. • The synergistic effect of CoC x /FeCo and N-doped carbon results in the activity. Abstract Metal-organic framework derived materials have a great promise as non-precious metal-based electrocatalysts for large-scale applications of energy storage and transition devices with low-cost and high efficiency. Here, we report a high performance core-shell-structured nitrogen-doped CoC x /FeCo@C/reduced graphene oxide (rGO) hybrid, which is derived from Fe-doped Co 3 [Co(CN) 6 ] 2 MOFs, as bifunctional catalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Structure characterizations show that the carbon shell of CoC x /FeCo and graphene support are bonded to each other, which offer a large surface area and stable anchoring sites for the CoC x /FeCo. Electrochemical tests show that N-doped CoC x /FeCo@C/rGO hybrid exhibits superior onset potential (1.0183 V vs RHE), half-wave potential (0.9653 V vs RHE), peak current intensity (0.9233 mA/cm−2) and long-term durability for ORR than those of Pt/C (onset potential, half-wave potential and peak current intensity are 1.0174 V and 0.9213 V, 0.8233 mA/cm−2, respectively) in 0.1 M KOH electrolyte. The overpotential of the hybrid for OER is only ∼390 mV at a current intensity of 10 mA/cm−2, which is close to that of the RuO 2. The excellent electrocatalytic properties of this hybrid make it a great potential to be substitute for precious-based catalysts for ORR and OER in fuel cells and water splitting. [ABSTRACT FROM AUTHOR]

• γ-graphyne nanoribbons are promising bifunctional electrocatalysts for ORR and HER. • Δ E H is a general energy descriptor for designing bifunctional electrocatalysts. • Light gradient boosting machine could predict electrocatalytic activities. Carbon-based metal free materials (CMFCs) as electrocatalysts have been a hot issue and are receiving growing attention. In this paper, we applied intensive density functional theory (DFT) calculations to study the electrocatalytic activities of γ-graphyne nanoribbons (γGyNRs) toward the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). Our results revealed γGyNRs to be excellent bifunctional CMFCs after functionalization by termination or N-doping at the edge to introduce proper spin densities. The scaling relationship analysis enhanced our earlier understanding that the binding strength of H atom (Δ E H) is a general descriptor for designing bifunctional electrocatalysts for HER and ORR. Further study revealed that the light gradient boosting machine is a promising machine learning algorithm to accurately predict the electrocatalytic activities of γGyNRs. Feature importance analysis suggested that the surrounding environment of the active site plays a more significant role than we previously anticipated. Overall, we suggest promising γGyNRs as HER and ORR bifunctional electrocatalysts for the first time and provide deeper insight into the reaction mechanism, which is beneficial for the rational design of novel CMFCs. [ABSTRACT FROM AUTHOR]

• Few-layered ReSe 2 nanoflakes are vertically arranged on rGO. • Mechanism of vertical growth of ReSe 2 on rGO is clarified by DFT calculation. • Plentiful exposed edges/corners on ReSe 2 facilitate the generation of active sites for electrocatalysis. • Improved electrical conductivity and electrochemical stability of ReSe 2 are realized after hybrid with rGO. • Prominent HER performance is measured with a low overpotential and small Tafel slope. Hydrogen evolution reaction (HER) by water splitting has made a significant contribution to producing large amounts of hydrogen gas as the next generation fuel. Development of highly efficient, economically viable, and electrochemically stable HER electrocatalysts has accordingly become a prerequisite for practical implementation of large scale water electrolysis. Mono/few-layered transition metal dichalcogenide (TMD) based HER-electrocatalysts have recently garnered great interest due to their diverse tunable electrochemical properties. However, they still face intrinsic limitations such as self-aggregation, rare active sites, high electrical resistance, and long-term electrochemical instability. To tackle these challenges, we designed and synthesized a novel electrocatalyst comprising active site-rich rhenium diselenide (ReSe 2) nanoflakes perpendicularly anchored on a reduced graphene oxide (rGO) nanosheet support via a facile one-step hydrothermal synthesis. The rGO support provides a growing platform for few-layered ReSe 2 nanoflakes while facilitating plentiful exposure of edge/corner sites of ReSe 2 , highly desirable for maximizing the catalytic activity of ReSe 2 @rGO. The synthesized ReSe 2 @rGO exhibits a low overpotential of 145.3 mV at a current density of 10 mA·cm−2 with a Tafel slope of 40.7 mV·dec−1 for the HER process due to the synergistic combination of high surface density of unsaturated coordination sites, remarkably accelerated electron transfer, and enhanced electrochemical stability. This outcome suggests using structurally regulated hybridization of TMDs and graphene as a platform toolkit for developing high performance HER catalysts. [ABSTRACT FROM AUTHOR]