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Electrocatalytic nitrate reduction reaction (NitRR) is an energy-saving and environmentally benign approach to synthesizing ammonia under ambient conditions. However, the development of noble metal-free catalysts with high activity and selectivity is still a significant challenge. In this study, uniformly dispersed amorphous CoBx nanoparticles supported on carbon paper were synthesized VIA a simple wet chemical reduction method. As an efficient nitrate reduction electrocatalyst, CoBx exhibited a maximum faradaic efficiency of 94.00 ± 1.67% and a yield rate of up to 0.787 ± 0.028 mmol h−1 cm−2 for ammonia production. The enhanced NitRR performance could be attributed to a partial electron transfer from B to Co, which is necessary for optimizing the adsorption energies of the reaction intermediates and facilitating electron transport. Thus, selective and cost-effective electroreduction of nitrates to ammonia can be achieved using CoBx nanoparticles. [ABSTRACT FROM AUTHOR]

Photoelectrochemical reduction of CO2 is a promising approach for renewable fuel production. We herein report a novel strategy for preparation of hybrid photocathodes by immobilizing molecular cobalt catalysts on TiO2‐protected n+‐p Si electrodes (Si|TiO2) coated with multiwalled carbon nanotubes (CNTs) by π–π stacking. Upon loading a composite of CoII(BrqPy) (BrqPy=4′,4′′‐bis(4‐bromophenyl)‐2,2′ : 6′,2′′ : 6′′,2′′′‐quaterpyridine) catalyst and CNT on Si|TiO2, a stable 1‐Sun photocurrent density of −1.5 mA cm−2 was sustained over 2 h in a neutral aqueous solution with unity Faradaic efficiency and selectivity for CO production at a bias of zero overpotential (−0.11 V vs. RHE), associated with a turnover frequency (TOFCO) of 2.7 s−1. Extending the photoelectrocatalysis to 10 h, a remarkable turnover number (TONCO) of 57000 was obtained. The high performance shown here is substantially improved from the previously reported photocathodes relying on covalently anchored catalysts. [ABSTRACT FROM AUTHOR]

The development of highly active and stable non-precious metal electrocatalysts is of great significance for energy conversion with the oxygen evolution reaction (OER) being a rate-determining step. Herein, we report a hybrid material bearing a three-dimensional (3D) core–shell hierarchical structure, in which binary metal–organic framework nanosheets (NiFe-MOF NSs) are rationally decorated on NiSex nanosheet (NS) arrays supported on Ni foam (NF). With this approach, the highly conductive NiSex NSs ensure rapid charge transfer, the NiFe-MOF NSs provide a large number of exposed active sites, and the 3D hierarchical structure benefits gas release and electrolyte diffusion. As a result the NiFe-MOF/NiSex/NF electrode delivers current densities of 10 and 100 mA cm−2 at overpotentials of 198 and 230 mV and reveals a low Tafel slope of 30.6 mV dec−1 toward the OER. When NiFe-MOF/NiSex/NF was used as both the anode and cathode for overall water splitting, the potential to deliver a current density of 10 mA cm−2 was 1.59 V, lower than that for the benchmark IrO2/NF(+)‖Pt/C/NF(−) system (1.66 V at 10 mA cm−2). [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) are promising catalysts for electrochemical reactions. Herein, self-supported NiFe-MOF nanoplates grown on Ni foam (NF) were prepared with iron carbonate hydroxide nanosheets (FeCH NSs) as a semisacrificial template and evaluated for the electrocatalytic oxygen evolution reaction (OER). In this approach, the porous FeCH NSs not only serve as the iron source of NiFe-MOF, but also slow down the leaching of Ni ions from the substrate, thus playing a unique role in regulating the morphology of NiFe-MOF with reduced thickness and sizes, enabling rapid electron transfer and mass transport. The resultant NiFe-MOF/FeCH-NF electrode showed higher activity than FeCH template-free electrodes and superior OER performance over other MOF based binder-free OER electrodes. A current density of 10 mA cm−2 was obtained at a low overpotential of 200 mV with excellent durability in alkaline solution. Raman and TEM measurements reveal the partial transformation of NiFe-MOF to hydroxide during water oxidation. [ABSTRACT FROM AUTHOR]