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Rechargeable Zn-air batteries (ZABs) are promising candidates for next-generation sustainable energy storage due to high theoretical energy density and inherent safety. For further practical applications, in addition to developing bifunctional cathode catalysts, there is still a significant performance bottleneck of poor oxygen utilization efficiency in conventional air cathodes, which is often overlooked. To address this problem, a novel “gas-breathing” integrated air diffusion electrode based on B,N-codoped carbon (BN-C/ADE) is designed, which combines gas-diffusion layers and catalyst layers into a single architecture. The hydrophobic diffusion layer with substantial channels promotes active diffusion of oxygen from air atmosphere to reaction interface without the need for an air pump. Consequently, compared with the conventional cathode, a reduced overpotential, higher power density (118.5 mW cm−2) and long lifespan (over 170 h) are obtained for liquid ZABs based on BN-C/ADE, even without external oxygen-pumping equipment, profiting from higher oxygen utilization and transfer efficiency.

Developing efficient electrocatalysts for direct N2 electrolysis that includes two key reactions of oxygen evolution reaction (OER) at the anode and nitrogen reduction reaction (NRR) at the cathode is an appealing yet challenging task. Herein, Ni foam (NF) supported sisal-like porous MoO2 nanosheet array (MoO2/NF) was synthesized through a facile hydrothermal and subsequent annealing process. It is shown that in the NRR process the Mo4+ in MoO2/NF is more favorable in an associative mechanism of NRR than Mo6+ in MoO3/NF, thus yielding an impressive ammonia electrosynthesis activity (NH3 yield rate: 9.56 μg h−1 cm−2; Faradaic efficiency: 5.14%) in 0.1 M KOH. Moreover, the sisal-like porous nanosheet array structure not only provides a high surface area for abundant accessible active sites, but also limits the coalescence of gas bubbles, enabling active sites better exposed to nitrogen by removing the small gas bubbles rapidly. The MoO2/NF also shows excellent performance for the OER in 0.1 M KOH, exhibiting a small overpotential of 340 mV to realize a current density of 10 mA cm−2. In two-electrode full N2 electrolysis, a remarkable ammonia production performance with an ammonia yield of 5.73 μg h−1 cm−2, an FE of 15.8%, and good long-term stability for at least 24 h is obtained.

Developing controllable and facile devices beyond traditional N2 electrocatalysis cell is critical for the commercial production of NH3 through electrochemical N2 reduction reaction (NRR) under ambient condition. Herein, the aqueous Al-N2 battery, fabricated by coupling the hollow molybdenum phosphate microspheres as cathode and the Al plate as anode within KOH electrolyte, was assembled for the electrochemical reduction of N2 to NH3 and power generation during the discharge process. Benefiting from the desirable active components and the structural advantages, the hollow molybdenum phosphate microspheres derived from molybdenum phosphonates exhibit high NH3 yield rate of 18.66 μg h−1 mgcat.-1 with the Faradaic efficiency of 9.04% at − 0.2 V vs. reversible hydrogen electrode, associated with excellent robustness for cycling operation. The Mo4+ species of molybdenum phosphates are verified as the active components for NRR through the associative reaction pathway. When measured in the flow battery configuration with flowing N2 during discharge, the formed Al-N2 battery delivers the high NH3 yield rate of 13.47 μg h−1 mgcat.-1 and Faradaic efficiency of 5.06% at 1.0 V vs. Al(OH)4−/Al, which can be stably maintained in discharge cycling tests over 20 cycles. Moreover, the peak power density of 2.37 mW cm−2 and the long-term energy output are still achieved by this Al-N2 battery during the discharge process. This work not only supplies some guidelines for the rational design of active NRR electrocatalysts from earth-abundant elements but also provides a reasonable and promising devices for efficient electrochemical N2 fixation and power generation.

Chemical doping is adopted to tune the work function and electrical conductivity of carbon counter electrode (CE) in HTM-free organometallic halide perovskite solar cells (PSCs). In this work, the boron and phosphorus co-doped carbon (BPC) CE is constructed by coating a B doped carbon layer onto the P-doped carbon (PC). The work function of BPC CE with B/P co-doping (B: 2.68 at.%, P: 2.23 at.%) is thus regulated to 5.12 eV from the 5.01 eV of pure carbon and 4.81 eV of PC, and the sheet resistance is modulated to 8.41 Ω sq −1 from 14.75 Ω sq −1 of pure carbon and 7.89 Ω sq −1 of PC. As a consequence, the BPC-based PSCs deliver a power conversion efficiency of 6.78%, higher than those of pristine carbon (3.72%), PC (5.39%) and BC (5.20%) based PSCs, and even comparable to that of conventional Au-based device (7.22%), due to the enhanced hole extraction ability and the maintained high electronic conductivity. Moreover, the good stability in ambient condition over a period of 720 h is also demonstrated in the BPC-based PSCs. The successful application of BPC CE in PSCs shows a promising way for fabricating low-cost, large-scale and highly efficient PSCs in future.

Red mud was activated by digestion in hydrochloric acid and re-precipitation with ammonia, and the activated red mud (ARM) was used as the support for preparation of CuO/ARM catalysts by a simple deposition–precipitation method. The prepared catalysts possessed well-structured porosity and high surface area, as characterized by X-ray diffraction, Fourier transform infrared spectroscopy, H 2 -temperature-programmed reduction, X-ray photoelectron spectroscopy, and nitrogen sorption techniques. High activity was observed for CO oxidation on the resultant CuO/ARM catalysts, and the CuO content and precalcination temperature had significant impacts on the catalytic properties. The catalyst calcined at 200 °C with 20% CuO loading amount demonstrated the highest catalytic activity, suggesting the CuO/ARM as a promising catalyst in the CO oxidation reaction, on the sake of the utilization of waste solids with much low cost of ARM.

Hybridization of non-precious metals with advanced carbon monolith provides a promising approach to substitute noble metal catalysts for various electrochemical reactions. The structural and electronic properties of non-precious metals significantly affect electrocatalytic performance, which depends on the physicochemical structure of carbon substrates and the types of metal components. Herein, binary FeNi phosphide nanoparticles coupled with N,P-modified carbon nanosheets were fabricated through an universal carbonization-phosphorization approach. Besides the structural advantage of 2D nanosheets, the electronic structure change of bimetallic FeNi phosphides via modulating Fe/Ni ratio is another reason responded for the exceptional activities with reduced overpotentials of this hybridized catalyst for both hydrogen evolution, oxygen evolution and oxygen reduction reactions. Furthermore, by employing the fabricated materials as electrode catalysts for overall water splitting and rechargeable Zn-air batteries with liquid and solid-state electrolytes, excellent performances are achieved in these energy conversion and storage devices, revealing the significant feasibility for practical applications.

A new micro-nanostructured composite (NOMC-Ni@NCNTs) of Ni-encapsulated and N-doped carbon nanotubes (Ni@NCNTs) pinned on N-doped ordered mesoporous carbon (NOMC) is constructed by a two-step synthesis strategy. The strategy involves the self-assembly preparation of water-soluble phenolic resin/F127 colloid by a hydrothermal route and the subsequent catalytic pyrolysis of as-prepared phenolic resin/F127 copolymer and melamine with nickel acetate as Ni source and self-generated catalyst, leading to the in situ growth of dispersive Ni@NCNTs pinned on NOMC through the Ni junction. In the resultant NOMC-Ni@NCNTs, the NOMC shows reduced particle size and shortened mesopore channel length of 15–30 μm compared to 850 μm-2 mm of pristine NOMC. The pinned Ni@NCNTs constructs a 3D conductive scaffold in the composite and the conductivity is correspondingly raised from 20.4 S cm−1 of pristine NOMC to 254.1 S cm−1 of NOMC-Ni@NCNTs. The particle size, mesoporosity and surface area of NOMC-Ni@NCNTs composite are also flexibly regulated by tailoring the relative content of Ni@NCNTs and NOMC. The new-structured NOMC-Ni@NCNTs composites are developed as counter electrode (CE) materials for DSSCs, which demonstrates an excellent catalytic activity towards I 3 - reduction. The optimum NOMC-Ni@NCNTs CE delivers a low charge-transfer resistance of 2.21 Ω and the assembled DSSC achieves a high power conversion efficiency of 8.39%. Moreover, the NOMC-Ni@NCNTs CE based DSSC also manifests a preeminent electrochemical stability in corrosive I - / I 3 - electrolyte with a remnant efficiency of 7.82% after 72 h of illumination. The outstanding electrocatalytic performance is mainly correlated with their unique architecture, in which the pinned Ni@NCNTs conductive substrate accelerates the electron transportation among NOMC micron-particles, and the amorphous NOMC with short-range mesopores accelerates the electrolyte diffusion and supplies abundant ions-accessible defects for I 3 - reduction.

The modification of electronic structure in heterogeneous catalysts has been particularly proven as one of efficient approaches for enhancing the catalytic performances in redox. Herein, phosphorus-doped g-C3N4 nanosheets with atomically dispersed V-based nanocomposites (V/P-CN) were fabricated through a facile organophosphonic acid-modified co-condensation route. The use of organophosphonic acid not only achieves the in-situ P-doping but also tailors the texture of the synthesized V/P-CN, leading to narrow band gap, electron-enriched structure, nanosheet morphology, abundant mesh-like pores and enlarged surface area. Series of physicochemical and electrochemical characterizations indicate the enhanced electron transfer from the P-doped g-C3N4 to V-based nanocomposites. The heterojunction-induced electron–enriched structure of V-based nanocomposites in V/P-CN endows with the impressive intrinsic oxidative desulfurization activities. Radical scavenger experiment further suggests the significant electron interaction in the heterojunction catalysts favors the enriched electron dispersion around V-based active species and employs as rate-determining step for oxidative desulfurization. This work offers a facile but economic and powerful method to modulate the structure of the heterojunction catalysts for green catalysis, especially redox reactions.

Highly ordered, ordered and disordered mesoporous carbons were prepared by an organic–organic self-assembly method with different molar ratios of formaldehyde to resorcinol (F/R) under the catalysis of citric acid. The mesoporous carbon synthesized with the F/R ratio of 2 possesses highly ordered pore system and large surface area, while the ones with the F/R ratio of 1 and 3 have an ordered and a disordered wormhole-like mesostructure, respectively. These three kinds of mesoporous carbons were utilized as counter electrode (CE) materials for dye-sensitized solar cells (DSSCs) and the effect of structural mesopore ordering on the photovoltaic performance was investigated. The cell assembled with highly ordered mesoporous carbon CE showed an excellent energy conversion efficiency of 6.06%, which is comparable to the one with Pt CE (6.29%), whereas ordered mesoporous carbon and disordered mesoporous carbon CEs based cells exhibited relatively poor photovoltaic performance at the same testing conditions. The enhanced catalytic capability of highly ordered mesoporous carbon CE is intrinsically attributed to the straight channels of long-range highly ordered 2-D hexagonal mesopores, which accelerates the diffusion of redox species and facilitates the charge-transfer process. The synthesized highly ordered mesoporous carbon with outstanding catalytic activity could be an alternative to replace Pt for high-efficiency DSSC CE.

Mesoporous carbon nitride (MCN) and carbon nitride–carbon (MCN/C) composites with a partly graphitized structure are synthesized by using mesoporous silica SBA-15 as a hard template and ethylenediamine and carbon tetrachloride as precursors, possessing uniform mesopore size of 6.3 nm, high surface area of 278–338 m 2 /g, and high nitrogen content of 20.5–24.9% with abundant basic sites. The synthesized MCN and MCN/C composites are used as adsorbents for CO 2 capture, showing high adsorption capacity and good reusability. The presence of carbon coating layer in MCN/C composites introduced more micropores, which favored the capture of CO 2 , exhibiting high CO 2 capture capacity of 3.05 mmol/g at 0 °C and 2.35 mmol/g at 25 °C and 760 mm Hg, with good CO 2 /N 2 selectivity and excellent regeneration stability.

Nitrogen-doped carbon materials with hierarchically porous structure were prepared by employing meso-/macroporous titania (MMT) as exotemplate with the use of Vitamin B6 (VB6) as both the carbon precursor and the nitrogen source for elemental doping. The synthesized materials were characterized by N 2 sorption, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The obtained N-doped carbon materials have a multi-scaled porous hierarchy with pore sizes ranging from micropores, mesopores to macropores, and their morphology can be easily tuned through a simple adjustment of the weight ratio of VB6 to MMT. The different chemical state (pyridine-like N, quaternary N and oxidized N) and the content of nitrogen were analyzed by XPS. The prepared materials were used as the adsorbents for lysozyme. The effect of nitrogen doping on the lysozyme adsorption capability was investigated by comparison of the lysozyme adsorption behavior on the nitrogen-doped and nitrogen-free carbon materials with a similar pore structure. It was found that the nitrogen-containing carbon had higher adsorption capacity of lysozyme than that of the nitrogen-free carbons.

Zirconium ribonucleotides were grafted onto SBA-15 by a one-pot condensation process using ZrOCl2 and 5′-adenylic acid (or 5′-cytidylic acid) as precursors. The ordered mesoporous structure with high surface area was well preserved in the obtained materials, exhibiting high capacity for CO2 capture of 1.96–1.99 mmol g−1 at 25 °C and 1.0 atm, with excellent reusability. The large CO2 capture capacity was comparable to or even higher than the previously reported amino functionalized mesoporous silica materials, which benefited from the large amount of amino and hydroxyl groups in the hybrid pore wall. It was the first illustration of substituted phosphate surface functionalized mesoporous silica materials, which would open a new area for the preparation of hybrid materials from biomolecules.

Mesoporous titania–silica–phosphonate (TSP) hybrid materials with different Si/Ti molar ratios have been synthesized by triconstituent assembly through oil-in-water microemulsion strategy with the use of Si(OEt)4, TiCl4 and sodium salt of ethylene diamine tetra(methylene phosphonic acid) as Si, Ti and P sources, respectively, and cetyltrimethylammonium bromide as surfactant template. The integration of silica into titania–phosphonate hybrids resulted in the improvement of regularity of mesoporous structure and the enlargement of surface area and pore volume of the hybrid materials, confirmed by low-angle powder X-ray diffraction, transmission electron microscopy and nitrogen adsorption–desorption analysis. The synthesized TSP triconstituent hybrid mesoporous materials have a preferable BET surface area up to 670 m2/g with large pore volume of 1.1 cm3/g. And the adsorption measurements of the synthesized TSP materials for CO2 in gas phase and Cd(II) ions in liquid phase were tested, indicating their potential applications as multifunctional adsorbents for environmental protection.

Carbon-modified TiO 2 photocatalysts with a hierarchical meso-/macroporous structure were prepared through direct hydrolyzation of n-tetrabutyl titanate in the dodecylamine solution and subsequent calcination under nitrogen atmosphere. The resulting photocatalysts were characterized by X-ray diffraction, scanning and transmission electron microscopy, nitrogen sorption analysis, X-ray photoelectron spectroscopy, and UV–vis spectroscopy. A well-defined hierarchical macrochannel-like structure of mesoporous nanoparticle assembly with a predominant anatase phase was observed in the synthesized carbon-modified titania materials, exhibiting obviously high absorption in the wavelength range of 400–800 nm. It is revealed that carbon could not only substitute partly Ti in the form of Ti–O–C bond but also substitute O in the form of O–Ti–C, besides amorphous interstitial carbon atoms were synchronously introduced, benefitting the improvement of solar light photocatalytic activity. The synthesized hierarchical carbon-modified titanias materials exhibited excellent photocatalytic performance in the photodegradation of Rhodamine B dye, suggesting their promising potential as effective solar photocatalysts for organic waste degradation.