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An electrochemical nitrogen reduction reaction (NRR) under mild conditions offers a promising alternative to the traditional Haber-Bosch process in converting abundant nitrogen (N2) to high value-added ammonia (NH3). In this work, iron phthalocyanine (FePc) was homogeneously immobilized on pyridine-functionalized carbon nanotubes to form a well-tuned electrocatalyst with an FeN5 active center (FePc-Py-CNT). Synchrotron X-ray absorption and Fourier transform infrared spectroscopy proved the presence of an Fe-N coordination bond between FePc and surface-bound pyridine. The resulting hybrid exhibited notably enhanced electrocatalytic NRR performance compared to FePc immobilized on CNTs based on pi-pi stacking interactions (FePc-CNT), resulting in doubled NH3 yield (21.7 mu g 1 h mgcat-1h-1) and Faradaic efficiency (22.2%). Theoretical calculations revealed that the axial coordination on FePc resulted in partial electron transfer from iron to pyridine, which efficiently suppresses the adsorption of H+ and improves the chemisorption of N2 at Fe sites. Meanwhile, the interfacial electron transfer was facilitated by pyridine as an electron transfer relay between FePc and CNTs. This work provides a unique strategy for the design of highly efficient NRR electrocatalysts at the molecular level., QC 20220706

Splitting water into hydrogen and oxygen by dye-sensitized photoelectrochemical cell (DSPEC) is a promising approach to solar fuels production. In this study, a series of pyridine derivatives as surface additives were modified on a molecular chromophore and water oxidation catalyst co-loaded TiO2 photoanode, TiO2 vertical bar RuP, 1 (RuP = Ru(4,4'-(PO3H2)(2)-2,2'-bipyridine)(2,2'-bipyridine)2, 1 = Ru(bda)(L)(2), (bda = 2,2'-bipyridine-6,6'-dicarboxylate, L = 10-(pyridin-4-yloxy)decyl)phosphonic acid). The addition of pyridine additives was found to result in up to 42% increase in photocurrent. Under simulated sun-light irradiation, TiO2 vertical bar RuP, 1, P-1 (P-1 = 4-Hydroxypyridine) produced a photo-current density of 1 mA/cm(2) at a bias of 0.4 V vs. NHE in acetate buffer. Moreover, the observed photocurrents are correlated with the electron-donating ability of the substituent groups on pyridine ring. Transient absorption measurements and electrochemical impedance spectroscopy revealed that surface-bound pyridine can effectively retard the back-electron transfer from the TiO2 conduction band to the oxidized dye, which is a major process responsible for energy loss in DSPECs., QC 20210629

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 NiSe(x)nanosheet (NS) arrays supported on Ni foam (NF). With this approach, the highly conductive NiSe(x)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))., QC 20201007

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., QC 20200103