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eNRR is a promisingly environment-friendly strategy to obtain ammonia under ambient conditions. For metal-based catalysts, the competitive adsorption of H+ over N2 remains the primary hurdle for high ammonia yield and faradaic efficiency. Carbon-based metal-free catalysts attract our attention for the potential of being promising NRR catalysts due to their natural low HER activity. In this study, we prepared a modified Zn-based metal–organic framework (Zn-BTC) decorated with Cl ions by simply adding NaCl in the synthetic process. The existence of Cl ions in the framework contributes to the generation of large pores during thermolysis. Moreover, –Cl and –COCl species were formed in situ and connected with carbon atoms in the defect area. Benefitting from such a structure, this catalyst achieves a high ammonia yield rate of 103.96 μg h−1 mgcat−1 and a faradaic efficiency of 21.71% at room temperature. Theoretical results also proved that the newly produced –COCl and –Cl functional groups could attract more electrons from adjacent carbon atoms due to their stronger electronegativity, thus improving its affinity towards N2 while lowering the HER activity as reactive sites. [ABSTRACT FROM AUTHOR]

In comparison to other electrocatalysts, graphene possesses two distinguished merits of superior electrical conductivity and anticorrosion performance. However, graphene and graphene oxide are electrocatalytically inert in hydrogen evolution reaction (HER) due to their electronic properties. Herein, for the first time, we report a highly active and stable graphene oxide electrocatalyst for the HER. The graphene oxide-encapsulated IrNi alloy catalyst (IrNi@OC) was prepared via the pyrolysis of Ir-doped Ni-BTC, which exhibited an excellent electrocatalytic activity for the HER, achieving 100 mA cm−2 at a low overpotential of 95 mV in 0.5 M H2SO4 and 10 mA cm−2 at 27 mV in 1 M KOH. Furthermore, these results are superior to those of commercial Pt/C. DFT calculations revealed that electrons were transferred from the IrNi alloy core to the graphene shell, and this process became more facile when graphene was decorated with O species, which tuned the electronic structure of the carbon atoms and made them favorable for the formation of C–H bonds, thereby decreasing the ΔGH* for the HER. [ABSTRACT FROM AUTHOR]

Biological heme–copper oxidases (HCOs) play a critical role in the four-electron, four-proton reduction of O2 to H2O in biosystems. HCOs exhibit high enzymatic activity due to their natural structure with heme–non-heme metal active sites, and the non-heme metal plays a role in conferring and fine-tuning the O2 reduction activity of the HCOs. Inspired by this binuclear active enzyme, herein, we designed an efficient electrocatalyst (Fe, Mn–N/C) for the oxygen reduction reaction, which contains two types of metal–Nx active site incorporated within the graphene framework of porous carbon. The catalyst displayed remarkable ORR performance with a half-potential of 0.904 V and kinetic current density of 33.33 mA cm−2, which is 4.9 times that of 20% Pt/C (6.76 mA cm−2). When the Fe, Mn–N/C catalyst was applied as an air electrode in a Zn–air battery, it exhibited a superior performance compared to commercial Pt/C. Its discharge curve showed that the change in output voltage was negligible at 20 mA cm−2 for 23 000 seconds (6.4 h). First principles calculations revealed that Fe, Mn–N/C needs less energy for the protonation of O* to OH* in ORR procedures compared with Fe–N/C. This catalyst, with its bimetal reactive center mimicking a metal enzyme, will pave a new way to design efficient electrocatalysts for the ORR in fuel cells. [ABSTRACT FROM AUTHOR]

Transition metal sulfides have attracted tremendous attention as promising lithium-ion anodes due to their natural abundance, intrinsic safety and high theoretical capacity. However, low conductivity and dramatic volume variation hinder their further application in lithium storage. Here, we reported a facile metal–organic framework (MOF)-derived self-template approach to prepare hollow cobalt sulfide polyhedra with vertically aligned metallic phase MoS2 nanosheets (denoted as CoS@1T-MoS2) as efficient anode materials for lithium storage. Benefiting from the high intrinsic conductivity of metallic phase MoS2, the hierarchical hollow framework, and the synergistic effect of interior cobalt sulfide and exterior metallic MoS2, the CoS@1T-MoS2 composite delivers a high reversible capacity of 1269 mA h g−1 after 100 cycles at a current density of 100 mA g−1 and 936 mA h g−1 at a current density of 1000 mA g−1 after 220 cycles. [ABSTRACT FROM AUTHOR]