A multi-dimensional hierarchical strategy building melamine sponge-derived tetrapod carbon supported cobalt-nickel tellurides 0D/3D nanohybrids for boosting hydrogen evolution and triiodide reduction reaction.

Designing efficient nanohybrid electrocatalysts with advanced structure is of great essential for energy conversion devices. Herein, a multi-dimensional hierarchical strategy is proposed to design melamine sponge-derived sulfur and nitrogen co-doped tetrapod carbon (SNTC) supported cobalt-nickel telluride (CoTe2/SNTC, NiTe2/SNTC, and CoNiTe2/SNTC) 1D/3D and 0D/3D nanohybrids for boosting hydrogen evolution reaction (HER) and triiodide reduction reaction (IRR). Among these, the CoNiTe2/SNTC 0D/3D hybrid exhibited superior catalytic activities and excellent electrochemical stability. In alkaline HER, the CoNiTe2/SNTC catalyst had a low Tafel slope of 72 mV dec-1, which was comparable to that of Pt/C (49 mV dec-1). CoNiTe2/SNTC served as counter electrode catalyst in photovoltaics and obtained a power conversion efficiency (PCE) of 8.11%, which is higher than that of Pt (7.25%). This investigation provides a novel approach for designing highly efficient nanohybrid catalysts in advanced energy devices.

Defect engineering tuning electron structure of biphasic tungsten-based chalcogenide heterostructure improves its catalytic activity for hydrogen evolution and triiodide reduction.

The design and exploration of high-efficiency and low-cost electrode catalysts are of great significance to the development of novel energy conversion technologies. In this work, metal and nonmetal heteroatoms co-doped biphasic tungsten-based chalcogenide heterostructured catalyst (Co-WS2/P-WO2.9) with rich defects is successfully synthesized by a vulcanization technique. The electrocatalytic performance of WS2/WO3 in the hydrogen evolution reaction (HER) and triiodide reduction reaction is significantly enhanced by modifying and optimizing its electronic structure through a defect engineering strategy. As an electrocatalyst for HER, the optimized Co-WS2/P-WO2.9 exhibits a low overpotential at 10 mA cm-2 of 146 and 120 mV with small Tafel slopes of 86 and 74 mV dec-1 in alkaline and acidic electrolyte, respectively. In addition, a Co-WS2/P-WO2.9 assembled solar cell yields a short circuit current density of 15.85 mA cm-2, an open-circuit voltage of 0.74 V, a fill factor of 0.66, and a competitive power conversion efficiency (7.83%), which is comparable or higher than conventional Pt-based solar cell (16.02 mA cm-2, 0.70 V, 0.63, 7.14%). The formation of a heterostructure in Co-WS2/P-WO2.9 leads to the presence of a built-in electric field in the interfacial region between Co-WS2 and P-WO2.9, which leads to an increased open-circuit voltage from 0.70 V for Pt to 0.74 V for Co-WS2/P-WO2.9. This work can provide a technical support for developing high-performance heterostructured catalysts, which open up a way for improving catalytic performance of heterostructured catalysts in the field of electrocatalysis.

Ni and Fe nanoparticles, alloy and Ni/Fe-Nx coordination co-boost the catalytic activity of the carbon-based catalyst for triiodide reduction and hydrogen evolution reaction.

The design of high-performance early transition metal decorated carbon-based multiple active-site catalysts is of high significance for improving the efficiency of energy utilization. Highly dispersed Fe7Ni3 alloy, Ni and Fe metal nanoparticles and 1D carbon nanotubes (CNTs) decorated metal-nitrogen species (Me-Nx) anchored carbon-based catalysts (Ni NP|Ni-NDC, Fe NP|Fe-NDC, Fe7Ni3|Ni/Fe-NDC) are prepared by a facile in-situ chemical synthesis. As-prepared three nanohybrid catalysts exhibit exceptional catalytic ability and stability for the alkaline hydrogen evolution reaction (HER) and triiodide reduction reaction (IRR). The power conversion efficiency of the dye-sensitized solar cell with the Fe7Ni3|Ni/Fe-NDC counter electrode catalyst reaches 8.58%. The overpotential and corresponding Tafel slope of electrocatalytic water splitting with Fe7Ni3|Ni/Fe-NDC catalyst exhibit 129 mV and 68 mV dec-1 at the current density of 10 mA cm-2 in alkaline solution, respectively. The enhanced catalytic performance of the as-designed hybrid catalysts can be attributed to the synergistic coupling effect of various components (the dispersed Fe7Ni3 alloy, Ni and Fe metal nanoparticles, Ni/Fe-Nx active sites and 1D CNTs) of the hybrid catalyst.

Designing and Understanding the Outstanding Tri-Iodide Reduction of N-Coordinated Magnetic Metal Modified Defect-Rich Carbon Dodecahedrons in Photovoltaics.

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.

Boosting catalytic activity of niobium/tantalum-nitrogen active-sites for triiodide reduction in photovoltaics.

To fabricate high-quality catalysts with abundant active sites, a series of transition-metal-modified nitrogenous carbon catalysts (Ta-NOC, Nb-NOC, and Nb/Ta-NOC) was successfully fabricated via pyrolysis and ion exchange. Owing to the high conductivity and ion transport capacity of its unique nitrogen-carbon structure, and synergistic effect of dual-metal active sites on modulating electronic structure, Nb/Ta-NOC catalyst exhibited an excellent catalytic performance and a remarkable electrochemical stability in triiodide reduction reaction (IRR) and hydrogen evolution reaction (HER). Nb/Ta-NOC catalyst achieved an ideal conversion efficiency of 8.45% for IRR in solar cells, which was higher than that of Pt electrode (7.63%). Furthermore, Nb/Ta-NOC catalyst exhibited a small overpotential of 145 mV at a current density of 10 mA·cm-2 and a Tafel slope of 77 mV dec-1 for HER. This work provided a new approach for the rational design of the active-sites-rich electrocatalysts for energy conversion applications.