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[Display omitted] In this paper, we have developed a simple and efficient sulfur-amine chemistry strategy to prepare a three-dimensional (3D) porous Ti 3 C 2 T x composite with large amounts of N and S terminal groups. The well-designed 3D macroporous architecture presents enlarged interlayer spacing, large specific surface area, and unique porous structure, which successfully solves the re-stacking issue of MXene during storage and electrode fabrication. It is the amount of concentrated hydrochloric acid added to the S-EDA (ethylenediamine)/MXene colloidal suspension that is critical to the formation of 3D morphology. In addition, N and S terminals on MXene could improve the adsorption ability of K+. Owing to the synergistic effect of the structure design and terminal modification, the N, S codoped three-dimensional porous Ti 3 C 2 T x (3D-NSPM) material shows a high surface capacitive contribution and rapid diffusion kinetics for K+ and Na+. As a result, the as-prepared 3D-NSPM delivers high reversible capacity (237 and 273 mAh g−1 at 0.1 A g−1 for PIBs and SIBs, respectively), superb cycling stability (84.9% capacity retention after 10,000 cycles at 1 A g−1 in PIBs and 74.0% capacity retention after 2200 cycles at 1 A g−1 in SIBs), and excellent rate capability (111 and 196 mAh g−1 at 5 A g−1 for PIBs and SIBs, respectively), which are superior to other MXene-based anodes for PIBs and SIBs. Moreover, the described strategy provides a new insight for constructing the 3D porous structure from 2D building blocks beyond MXene. [ABSTRACT FROM AUTHOR]

The synergy between iron doping and (1 1 1) facet engineering in Fe-NiSe octahedron reinforces catalytic activity for IRR to yield impressive photovoltaic performance of DSSCs. [Display omitted] • The possibility of Fe-NiSe (1 1 1) as CE catalysts was investigated by DFT calculation. • The well-defined Fe-doped NiSe octahedron with (1 1 1) plane was synthesized. • Synergy between doping and facet engineering reinforces electrochemical behavior. • PCE can be further enhanced by introducing Fe heteroatom into NiSe (1 1 1). Reasonable design of cost-effective counter electrode (CE) catalysts for triiodide (I 3 −) reduction reaction (IRR) by simultaneously combining heteroatom doping and facet engineering is highly desired in iodine-based dye-sensitized solar cells (DSSCs), but really challenging. Herein, the density function theory (DFT) calculations were first conducted to demonstrate that the Fe-doped NiSe (1 1 1) showed an appropriate adsorption energy for I 3 −, increased number of metal active sites, reinforced charge-transfer ability, and strong interaction between 3 d states of metal sites and 5 p state of I 1 atoms in I 3 −, compared to NiSe (1 1 1). Based on this finding, the well-defined Fe-NiSe octahedron with exposed (1 1 1) plane (marked as Fe-NiSe (1 1 1)) and NiSe octahedron with the same exposed plane (named as NiSe (1 1 1)) are controllably synthesized. When the as-prepared Fe-NiSe (1 1 1) and NiSe (1 1 1) worked as CE catalysts, Fe-NiSe (1 1 1) exhibits improved electrochemical performance with higher power conversion efficiency (PCE) than NiSe (1 1 1), providing new opportunity to replace precious Pt for DSSCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • The carbonized recycled melamine sponge obtained excellent low-cost porous matrix. • FeNi@NCS shows lower reaction potential and higher electron transfer ability on UOR. • Successfully assembled the DBHPFC using urine as fuel. • DUHPFC presents excellent open circuit voltage. The direct urea fuel cell (DUFC) is a power generation equipment with urea-rich wastewater or urine as fuel source. It has the unique ability to purify sewage while simultaneously generating electricity, making it a highly efficient and environmentally friendly option. In this paper, pomegranate seed-like Ni nano-blocks and Fe nanosheets were synthesized by electrodeposition and chemical reduction and attached to the carbonized melamine sponge matrix. The N -doped carbon sponge (NCS) provided a large number of polyhedral holes, which allowed for efficient gas escape through channels. The combination of Fe reduces the initial urea oxidation potential, reaction activation energy and reaction resistance. The synthesized FeNi supported on N -doped carbon sponge composite (FeNi@NCS) has a catalytic current density of 625 mA cm−2 and a Tafel slope of 42.51 mV dec−1 for urea electrooxidation reaction (UOR). Assembling the direct urine-hydrogen peroxide fuel cell (DUrHPFC) resulted in the highest performance output. The open circuit voltage (OCV) was 0.98 V, and the peak power density reached 9.61 mW cm−2. The results show that the prepared catalyst provides an opportunity to solve the problems that hinder the development of urea green cycle at present. [ABSTRACT FROM AUTHOR]