ABSTRACT
Nitrogen-coordinated metal-modified carbon is regarded as a novel frontier electrocatalyst in energy conversion devices. However, the construction of intrinsic defects in a carbon matrix remains a great challenge. Herein, N-coordinated magnetic metal (Fe, Co) modified porous carbon dodecahedrons (Fe/Co-NPCD) with a large surface area, rich intrinsic defects, and evenly distributed metal-Nx species are successfully synthesized via the rational design of iron precursor and the bimetallic-organic frameworks. Because of a synergistic effect between N-coordinated dual magnetic metal active sites, the Fe/Co-NPCD exhibits exceptional electrocatalytic activity and electrochemical stability. A solar cell fabricates with the Fe/Co-NPCD yields an impressive power conversion efficiency of 8.35% in dye-sensitized solar cells, superior to that of mono-metal-doped carbon-based cells and conventional Pt-based cells. Furthermore, density functional theory calculations illustrate that Fe, Co, and N doping are in favor of improving the adsorption capacity of the catalyst for I3 - species by optimizing the magnetic momentum between the magnetic metal atoms, thereby upgrading its catalytic activity. This work develops a general strategy for synthesizing a high-performance defect-rich carbon-based catalyst, and offers valuable insight into the role of magnetic metals in catalysis, which can be used to guide the design of high-performance catalysts in the energy field.
ABSTRACT
Developing highly-efficient multifunctional electrocatalysts for energy conversion devices is of great importance. A sequence of nano-sized bimetal (Al, Cr, Fe) niobium oxide nanoparticles anchored on aloe peel-derived porous carbon skeleton hybrids (AN/APPC, CN/APPC, and FN/APPC) are successfully prepared via co-precipitation avenue and used as electrocatalysts for photovoltaics and alkaline hydrogen evolution reaction. Benefiting from the synergies between nano-sized metal niobium oxides and highly conductive porous carbon skeleton, these robust polycomponent hybrid electrocatalysts exhibit superior catalytic performances for accelerating the triiodide reduction and hydrogen evolution reaction. The solar cell with AN/APPC electrocatalyst achieves an outstanding device efficiency of 7.31%, superior to that with Pt (6.84%), and the AN/APPC electrocatalyst exhibit an overpotential (131.6 mV) when the current density is 10 mA cm-2 and Tafel slope (54 mV dec-1) in 1 M KOH for hydrogen evolution reaction. The AN/APPC electrocatalysts illustrate remarkable electrochemical durability in both I3-/I- electrolyte and alkaline media. Furthermore, the catalytic mechanism was clarified both from the electronic structure and work function through first-principle density functional theory (DFT) calculations. This work opens a new avenue for electrocatalysis field via using nano-sized porous bio-carbon skeleton loaded with niobium-based binary metal.
ABSTRACT
Manganese tungstate (MnWO4), zinc tungstate (ZnWO4), and copper tungstate (CuWO4) embedded biomass-derived carbon (MWO-C, ZWO-C, CWO-C) was synthesized by hydrothermal treatment and investigated as counter electrode (CE) catalysts to test electrochemical activity. Biomass-derived carbon was used as the shape controlling agent, which changed the morphology of MWO from spherical to spindle-like. Owing to the synergistic effect between tungsten-based bimetal oxides and biomass-derived carbon, the MWO-C, ZWO-C, and CWO-C catalysts exhibited enhanced electrochemical performance in dye-sensitized solar cells (DSSCs) system. The MWO-C, ZWO-C and CWO-C catalysts in DSSCs showed outstanding power conversion efficiency (PCE) of 7.33%, 7.61%, and 6.52%, respectively, as compared with 7.04% for Pt based devices. Biomass-derived carbon improves the catalytic properties of tungsten-based nanohybrids. The results showed that biomass-derived carbon-enhanced inorganic compound as CE catalysts are promising alternatives to Pt-based CE catalysts for energy conversion devices.
