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Self-adaptive electrocatalysis of inorganic materials was proposed and its origin, basic principles, and recent advances were discussed toward the fabrication of self-adaptive cycles for sustainable electrocatalysis.

Currently most of research efforts for selective electrocatalysis CO2 reduction to C2+ products have relied on crystalline Cu-based catalysts; amorphous Cu with abundant low-coordinated atoms holds greater promise for this conversion yet remains relatively underexplored. Here we report an amorphous urchin-like Cu@nanosilica hybrid synthesized by electrostatic coupling Si polyanions with Cu salt in hydrothermal processes. The Cu@nanosilica electrocatalyst displays excellent CO2 electroreduction activity and selectivity with a Faradic efficiency of 70.5% for C2+ product production, and higher stability compared to the crystalline Cu counterpart. The solar-driven CO2 electrolysis yields an energy efficiency of 20% for C2+ product production. Mechanism study reveals that the urchin-like Cu@nanosilica catalyst with amorphous Cu/Cu+ dispersion enhances CO2 adsorption and activation to facilitate generation of CO2−* and possible CO* intermediates, and suppresses hydrogen evolution concurrently. The combined effects of both aspects promote efficient C2+ product production from CO2 electroreduction.

Carbon-based metal-free catalysts exhibit great applications in electrochemical CO2 reduction (ECR), while most studies merely focus on large-sized carbons with limited ratio of surface atoms for engineering to create surface active centers. Here, we report a joint treatment of C60 by heating and plasma to induce a dramatic performance promotion during ECR. The electrochemical measurements indicate the Faraday efficiency for ECR toward CO production kept at high level over 80% in a wide potential region from − 0.4 to − 0.7 V versus RHE, with the highest value reaching 96.8%. The physical characterization reveals that fragmentation of C60 occurs together with N/O doping, both of which could induce change in electron structure, causing the formation of *COOH intermediate and ultimately leading to the optimized activity and selectivity for CO production. This treatment route was further revealed to be applicative for other carbon materials, e.g., single-walled carbon nanotube, to promote its ECR activity and selectivity.

Manganese-based layered oxides are one of the most promising cathodes for Na-ion batteries, but the prospect of their practical application is challenged by high sensitivity to ambient air. The stacking structure of materials is critical to the aging mechanism between layered oxides and air, but there remains a lack of systematic study. Herein, comprehensive research on model materials P-type Na

Incorporation of ultrathin nanosheets with dopants/defects shows great potential to enable metal (oxy)-hydroxide electrocatalysts with enhanced oxygen evolution reaction (OER) performance via the regulation of atomic structure and bonding arrangements. However, it remains challenging in synthesis especially for such dual control and at large scale. In this study, we present a stepwise chemical oxidation route, involving phase transition and reconstruction processes, to access ultrathin CoOOH nanosheets with a thickness of ca. 4 nm and abundant oxygen vacancies. Other transition metals were also doped into CoOOH nanosheets through this strategy. Among them, the optimized FeCoOOH nanosheets demonstrated an efficient OER activity with overpotential as low as 252 mV (current density: 10 mA cm−2) and excellent stability. A high and stable solar-to-hydrogen efficiency of 10.5% was acquired when FeCoOOH nanosheets were used as the anode in a constructed water splitting device driven by solar energy. This study offers a noble and facile strategy for potentially scalable preparation of atom-modulated ultrathin metal (oxy)-hydroxide nanosheets, and also demonstrates the OER applications.

Exploring the simple yet well-controlled synthesis of atomically dispersed Pt catalysts is a crucial endeavour for harvesting clean hydrogen via the kinetics-favoured acidic electrochemical water splitting technique. Here we employed the use of defective carbon sheets by KOH etching as a substrate for the in situ surface reduction of Pt(IV) ions to prepare atomically dispersed Pt. Physical and electrochemical characterizations reveal a strong interaction between the carbon substrate and Pt species, providing the basis for the in situ surface reduction. The atomically dispersed Pt electrocatalyst exhibited high HER performance in a sulfuric acid electrolyte, with an overpotential as low as 55 mV at a current density of 100 mA cm-a, and better catalytic durability compared to the commercial Pt/C. The mechanism study revealed that the full utilization of atomically dispersed Pt and the optimized catalyst surface may enhance the recombination of adsorbed *H via the Volmer-Tafel mechanism to produce H2 at a high efficiency. In the light of high activity, durability, and low cost, the atomically dispersed Pt material is promising for acidic HER application.

Metal-CO2 batteries, an attractive technology for both energy storage and CO2 utilization, are typically classified into organic Li(Na)-CO2 batteries with a high energy density/output voltage and aqueous Zn-CO2 batteries with flexible chemical production. However, achieving both high-efficiency energy storage and flexible chemical production is still challenging. In this study, a reversible hybrid aqueous Li-CO2 battery is developed, integrating Li with an aqueous phase, which exhibits not only a high operating voltage and energy density but also highly selective formic acid production. Based on a Li plate as the anode, NaCl solution as the aqueous electrolyte, solid electrolyte Li1.5 Al0.5 Ge1.5 P3 O12 (LAGP) as a separator and Li+ transporter, and a bifunctional Pd-based electrocatalyst as the cathode, the resulting battery shows a high discharge voltage of up to 2.6 V, an outstanding energy conversion efficiency of above 80 %, and remarkable selectivity of CO2 -to-HCOOH conversion of up to 97 %. The related reaction mechanism is proposed as CO2 +2 Li+2 H+ ⇌HCOOH+2 Li+ .

Acidified water electrolysis with fast kinetics is widely regarded as a promising option for producing H

Atomization of noble metals enable their electrocatalysis applications with low cost, whereas the isolated mononuclear site after atomization might lead leads to limited performance. Herein, we present a general strategy of atomically confined alloying (ACA) to synthesize an electrocatalyst of single atom iridium-trapping cobalt nanosheets with dual-reactive Ir–Co sites. The atomic Ir@Co nanosheets (1.7 wt% Ir) exhibit excellent oxygen evolution reaction (OER) performance with a small overpotential (273 mV at 10 mA cm−2) and high stability, higher than that of the Ir/C catalyst (290 mV at 10 mA cm−2). More importantly, density functional theory (DFT) calculations combined with experiments demonstrated that water oxidation proceeded on atomic Ir@Co nanosheets via a dinuclear tandem mechanism, in which Ir–Co dual sites cooperatively worked in favour of the sequential transfer from Co–OH* to Ir–O* via a Co–O–Ir intermediate, and stabilization of OOH* species by hydrogen bonding interaction. The cooperative mechanism based on a dinuclear electrocatalyst by ACA is hoped to open up more possibilities of single atom noble metal electrocatalysts for various applications.

The design and construction of efficient electrode materials are significant for electrochemical energy conversion and storage technologies. The oxygen evolution reaction (OER) is a key process in water splitting devices and metal–air batteries. Herein, we report conductive metal–organic framework (C-MOF) nanowire arrays on carbon cloth as a promising electrocatalyst for OER. The pyrolysis-free C-MOF electrocatalyst can maintain intrinsic molecular active sites in the MOFs. The as-prepared electrode possesses overpotentials of ∼213 and 300 mV at 10 and 150 mA cm−2 and long-term stability in 1 M KOH, respectively. Control experiments and Fourier-transform extended X-ray absorption fine structure (EXAFS) and Mossbauer spectra indicate that the Fe doped in the Ni-based MOFs may serve as highly effective OER active sites. Density functional theory (DFT) calculations reveal an unusual self-adaptable property of the Fe active sites, which enables the OER intermediates to generate additional hydrogen bonds with the neighboring layer, thus lowering the free energy in the OER process. Our findings may provide an alternative method for developing MOF electrocatalysts in frontier potential applications.

Sustainable energy and environmental developments require exploring multi-functional energy conversion and storage, such as metal–air batteries, water splitting and CO2 electro-reduction, which is bottlenecked by the lack of multi-functional electrocatalysts. Herein, we designed and synthesized a Ni–N and P–O codoped graphene (NiPG) nanomaterial for trifunctionally electrocatalyzing the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and carbon dioxide reduction reaction (CDRR). Beyond the known role of P–O and Ni–N units for the OER/ORR and CDRR, separately, the P–O unit, which expressed high activity in the HER, was found to suppress the competitive HER towards enhanced CDRR on NiPG over Ni–N doped graphene, firstly. Besides, the Ni–N unit also promoted the OER/ORR over P–O doped graphene. Based on this trifunctional NiPG electrocatalyst, we realized dual-model Zn–CO2/Zn–O2 batteries, switched by supplying CO2 or O2. This work provides the novel design of multifunctional electrocatalysts and dual-model batteries for the versatile application demands of energy conversion and storage.

As a promising technique for CO2 fixation/utilization and energy conversion/storage, the metal-CO2 battery has been studied to improve its interconversion between CO2 and carbonates/oxalates. Herein, we propose and realize a reversible aqueous Zn-CO2 battery based on the reversible conversion between CO2 and liquid HCOOH on a bifunctional Pd cathode. The 3D porous Pd interconnected nanosheet with enriched edge and pore structure, has a highly electrochemical active surface to facilitate simultaneous selective CO2 reduction and HCOOH oxidation at low overpotentials. The resulting battery has a 1 V charge voltage, a cycling durability over 100 cycles, and a high energy efficiency of 81.2 %. The battery mechanism is proposed as Zn+CO2 +2 H+ +2 OH- ↔ ZnO+HCOOH+H2 O, through which the reversible conversion between CO2 and liquid HCOOH was realized.

Due to energy-efficient and green processes of photocatalysis, the visible-light-driven photocatalytic organic synthesis has developed greatly in the last decade. The well-known photocatalysts, RuII-polypyridyl complexes, have been extensively exploited in the synthesis of various chemicals. However, homogeneity of RuII-polypyridyl complexes makes their recycling difficult. Here, we show an effective strategy for boosting photocatalysis by incorporating [RuII(bpy)3] into a radical metal-organic framework (FJI-Y2). Recyclable photocatalyst FJI-Y2 can efficiently catalyze the cross-dehydrogenative coupling reactions of N-phenyltetrahydroisoquinoline derivatives with phosphite esters, forming medicinal α-aminoquinoline phosphonates. More importantly, the photocatalytic efficiency of FJI-Y2 is actually higher than its homogeneous counterpart [RuII(bpy)3]Cl2, because multiple intermolecular interactions between 1,4,5,8-naphthalenediimide radicals and [RuII(bpy)3] induce optimal photoinduced electron transfer process to expedite chemical conversion and recycling of catalysts. It is envisioned that MOFs containing radicals can be ideal platforms to incorporate more noble-metal photocatalysts for promoting photocatalysis.

Development of the electrochemical water splitting is impeded by the important yet sluggish half-reaction of oxygen evolution reaction (OER). Atomic dispersion of Fe Co species represents a new type of potential materials for OER. However, it is still highly challenging to exploit facile and efficient methods for such synthesis. Herein, we have developed a rapid mechanical ball milling approach to synthesize highly-dispersed Fe/Co/N on graphene as OER electrocatalyst, which displays high OER performance with overpotential of 288 mV at 10 mA cm−2 and no obvious decay after 9 h of continuous operation at 10 mA cm−2. This excellent electrocatalytic performance originates from atomic-scale accessible iron, cobalt and nitrogen electrocatalytic sites and highly conductive graphene. These results suggest feasibility of this facile and efficient ball milling method in synthesis of other electrocatalysts for various applications.

Alternatives to noble metal based electrocatalysts are vitally necessary to produce hydrogen from water at low overpotentials. Earlier research on tungsten based electrocatalyst has been mainly concentrated towards tungsten carbide (WC) and tungsten nitride (WN) as the potential electrocatalysts for hydrogen evolution reaction (HER), whereas tungsten carbide (W2C) has been least focused upon. Herein, we report a highly active novel strongly coupled tungsten-carbon-nitrogen complex (W2C-NC-WN complex) prepared by in situ carbonization method. This W2C-NC-WN complex exhibits a remarkable electrochemical performance for HER with a small onset potential of 33 mV vs. RHE and requires an overpotential (η) of 145 mV vs. RHE to render −10 mA cm−2 current density. The Tafel analysis demonstrates a slope of 96 mV dec−1 which is much better than WN (109.6 mV dec−1) and WC (142.4 mV dec−1). The strong coupling of W2C and WN within N-doped carbon (NC) framework brings about a significant enhancement in HER kinetics and faster electron transport due to the remarkable reduction in charge transfer resistance. The facile synthetic approach reported here, provides a powerful tool for the structurally controlled modification of the catalyst while simultaneously introducing active species.

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are of paramount importance towards to regenerative fuel cells and rechargeable metal-air batteries. Many efforts have been devoted to developing high active ORR and OER bifunctional electrocatalysts to improve the efficiency of devices. However, the possibility of using free solar energy in ORR/OER electrocatalysts to get higher efficiency in the devices has not yet been recognized. Herein, we report a photo-responsive bifunctional ORR/OER electrocatalyst with a built-in p-n heterojunction based on Ni12P5 nanoparticles (NPs) coupled strongly with nitrogen-doped carbon nanotubes (NCNT). The Ni12P5@NCNT hybrid catalyst exhibited unusually high catalytic activities for both ORR (onset potential at 0.90 V vs. RHE) and OER (η = 360 mV @10 mA cm−2) in 0.1 M KOH solution with a ΔE (EOERj = 10 - EORR1/2) = 0.82 V, comparable to that of its state-of-the-art counterparts (e.g., Pt for ORR, IrO2 for OER). Upon light irradiation (300 W Xenon lamp equipped with an AM 1.5G filter, 5 cm to electrode), the ΔE further decreased to 0.80 V. A rechargeable Zn-air battery devised from a Ni12P5@NCNT cathode in 6 M KOH/0.2 M Zn(Ac)2 exhibited a low charge-discharge voltage gap (~ 0.75 V @ 10 mA cm−2, charge potential = 1.94 V and discharge potential = 1.19 V) and a remarkable cycling stability over 500 cycles, which, upon the light irradiation, showed an even lower charge potential of 1.90 V and higher discharge potential of 1.22 V (i.e., a charge-discharge voltage gap: 0.68 V @ 10 mA cm−2). The irradiation caused also a concomitant increase in the round-trip efficiency from ~ 61.3% to ~ 64.2%. To demonstrate the potential applications in portable/wearable electronic devices, we have also developed all solid-state flexible photo-assisted rechargeable Zn-air batteries based on the Ni12P5@NCNT air electrode with high-performance in the both presence and absence of light irradiation. This conceptual demonstration of the first photo-responsive ORR/OER bifunctional catalyst is significant as it reveals a novel catalytic mechanism, from which a class of new bifunctional catalysts with further enhanced photo-responsive performance could be developed, using in other rechargeable metal-air batteries.

Global climate change and energy concerns trigger worldwide interest in sustainable, economical CO2 reductive transformation into valuable chemicals. However, traditional electro/thermo-catalysis strategies usually consume a large amount of energy and suffer from low efficiency. Herein, a three-dimensional porous fractal Zn cathode is synthesized by redox-coupled electrodeposition and it exhibits excellent electrocatalytic properties for CO2-to-CO conversion. Inspired by the coupling of a metal battery and CO2 electroreduction, a novel fuel-gas CO generating Li–CO2 battery is firstly realized with the as-prepared porous fractal Zn cathode. Meanwhile, CO formation can be easily tuned within a wide range of discharge currents and reach a maximum faradaic efficiency of up to 67%. Finally, based on gas and solid discharge product analysis, the related mechanism of CO main product production is proposed as 2Li+ + 2CO2 + 2e− → CO + Li2CO3. Hence the present work presents a new way for the further development of metal–CO2 batteries to generate useful chemicals and fuels besides electrical energy.

Metal-CO

To develop and improve electrocatalysts for promising energy conversion reactions, an in-depth understanding of their active sites is essential. In real operating conditions, the active sites could be subjected to various structural/chemical evolutions, as revealed recently by post-catalysis/in-situ characterizations. Insightful understanding suggests that multiple interactions between electric field, electrolyte, reactant/intermediate/resultant, and electrocatalyst increase the mutability of the electrocatalyst surfaces, triggering the surface evolution. Hence, the surface evolution causes the deviation of the initial design of active sites from the real ones. It calls for re-identification of active sites responsible for the observed activity and further provides more accurate guidelines for rational electrocatalytic design. This review reveals the origin of surface evolution, summarizes the general forms involving composition leaching, phase transformation, atom rearrangement, and metastable intermediate from typical electrocatalysts. It also proposes control strategies toward the formation or reservation of stable highly-active sites by atomic/defective modulation, interfacial coupling, structural optimization of pre-synthesis, and forming a protective layer. The active sites of typical electrocatalysts are identified and elucidated before and after the surface evolution. The current challenges in developing electrocatalysts addressing the definite structure-performance relationship, advanced characterization techniques, and strategies for more rigorous identification of real active sites after surface evolution are presented.

Progress in the development of efficient electrocatalysts for oxygen reduction reactions is imperative for various energy systems such as metal–air batteries and fuel cells. In this paper, an innovative porous two-dimensional (2D) poly-iron–phthalocyanine (PFe–Pc) based oxygen reduction electrocatalyst created with a simple solid-state chemical reaction without pyrolysis is reported. In this strategy, silicon dioxide nanoparticles play a pivotal role in preserving the Fe–N4 structure during the polymerization process and thereby assist in the development of a porous structure. The new polymerized phthalocyanine electrocatalyst with tuned porous structure, improved specific surface area and more exposed catalytic active sites via the 2D structure shows an excellent performance towards an oxygen reduction reaction in alkaline media. The onset potential (E = 1.033 V) and limiting current density (I = 5.58 mA cm−2) are much better than those obtained with the commercial 20% platinum/carbon electrocatalyst (1.046 V and 4.89 mA cm−2) and also show better stability and tolerance to methanol crossover. For practical applications, a zinc–air (Zn–air) battery and methanol fuel cell equipped with the PFe–Pc electrocatalyst as an air cathode reveal a high open circuit voltage and maximum power output (1.0 V and 23.6 mW cm−2 for a methanol fuel cell, and 1.6 V and 192 mW cm−2 for the liquid Zn–air battery). In addition, using the PFe–Pc electrocatalyst as an air cathode in a flexible cable-type Zn–air battery exhibits excellent performance with an open-circuit voltage of 1.409 V. This novel porous 2D PFe–Pc has been designed logically using a new, simple strategy with ultrahigh electrochemical performances in Zn–air batteries and methanol fuel cell applications.

Carbon has been regarded as one of the most attractive cathode materials for non-aqueous lithium-oxygen batteries due to its excellent conductivity, high specific area, large porosity, and low cost. However, a key disadvantage of carbon electrodes lies in the fact that carbon may react with Li2O2 and electrolyte to form irreversible side products (e.g. Li2CO3) at the active surfaces, leading to a high charge voltage and a short cycling life. In this work, we address this issue by decorating NiO and RuO2 nanoparticles onto carbon surfaces. It is demonstrated that the NiO-RuO2 nanoparticle-decorated carbon electrode not only catalyzes both the oxygen reduction and evolution reactions, but also promotes the decomposition of side products. As a result, the battery fitted with the novel carbon cathode delivers a capacity of 3653 mAh g−1 at a current density of 400 mA g−1, with a charge plateau of 4.01 V. This performance is 440 mV lower than that of the battery fitted with a pristine carbon cathode. The present cathode is also able to operate for 50 cycles without capacity decay at a fixed capacity of 1000 mAh g−1, which is more than twice the cycle number of that of the pristine carbon cathode.

Electrochemical CO2 reduction (ECR) to fuels and chemicals driven by renewable energy sources represents a promising solution to current energy, resource, and environmental issues. Carbon-based metal-free electrocatalysts exhibit great prospects for ECR based on their multi-dimensionally tunable structures from atom/molecule level to nano/microscale and the resulting controllable performance. However, ECR on metal-free sites (MFS) still suffers from low control over activity and selectivity, resulting from a limited mechanism understanding of complicated interactions between MFS and intermediates. This review presents that most optimizations refer to multidimensional structure modifications of MFS involving inner p-orbital electron structure, surface structure and/or outer environment, which vary intermediate adsorption. Absolute and relative changes of intermediate adsorption result in the lower-energy-barrier pathway to the products of CO, HCOOH, CH3OH, CH3CH2OH, etc. How engineering atomic dopant/defect/surface curvature, molecule modifier, nano/microscale pore structure, and external electrolyte/potential can alter the adsorption strength/density/configuration of ECR intermediates, is discussed. Adsorbed intermediates are detected by in situ techniques, and their variations for selectively ECR through different reaction pathways are described by Gibbs free energy calculations. Finally, challenges to rationally develop in situ techniques and theoretical simulation methods, and strategies for optimizing intermediate adsorption and reactivity toward desired ECR products are presented.

Metal-CO

As a promising technique for CO

Palladium (Pd)-based catalysts are appealing electro-catalysts for alcohol oxidation reaction in fuel cell, but still not efficient as the complicated oxidation process and sluggish kinetic. Here we rationally design and synthesize a PdRuBi/NG tri-metallic catalyst with space synergetic effect for enhanced ethylene glycol electro-oxidation, in which both Ru and Bi in the catalyst are synergistic effective in promoting catalytic activity of Pd catalytic interlayer by electronic effect and surface modification mechanism respectively. It shows 4.2 times higher peak current density towards ethylene glycol electro-oxidation than commercial Pd/C catalyst, and the catalytic durability is also greatly improved.

Gaining control over the size and dispersion of binary metal nanoparticles is critical in order to manipulate their catalytic properties. In this study, we demonstrate a facile and effective solid phase evolution approach to prepare a highly dispersed PtCu/C catalyst via a surface substitution and etching separation process with the Pt-decorated Cu particles on carbon as the precursors. It is demonstrated that the dispersion of metal nanoparticles in PtCu/C derived from the present solid phase evolution is better than that in PtCu/C (C) prepared from the co-reduction by NaBH 4 . As a result, the synthesized PtCu/C shows a larger electrochemically active surface area (ECSA) (48.6 m 2 g −1 ), higher mass (0.52 mA μg −1 ) and area activities (1.07 mA cm −2 ) than that of the PtCu/C (C) (37.9 m 2 g −1 , 0.34 mA μg −1 and 0.89 mA cm −2 , respectively). As compared to commercial Pt/C catalyst, PtCu/C exhibits ca. 2.5 times higher formic acid oxidation (FAO) activities (0.52 mA μg −1 and 1.07 mA cm −2 ). The tolerance toward CO poisoning is characterized by CO stripping, the result indicates that both onset (0.43 V) and peak (0.50 V) potentials of PtCu/C for CO oxidation show a negative shift of ca. 70 mV. More significantly, PtCu/C shows high stability in the acid solution, which can maintain 90.1% retention in ECSA after 1000 CV cycles. In addition, the solid separation method offers ease of manipulation, allowing the synthesis of a novel class of highly dispersed binary metal nanoparticles.

This work presents a modified chemical etching strategy to fabricate binary metal nanocatalysts with large active areas. The strategy employs PtCu alloy particles with Pt-rich outer layers as the precursor and manganese species to manipulate the acid leaching processes. X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy techniques are used to analyze the catalyst structures and the tuning mechanism of manganese species during etching. It is found that the introduction of manganese species allows more Pt active sites to be formed onto the catalyst surface after etching, possibly due to reduction in the number of Pt atoms enclosed inside particles. The electrochemically active surface area of the synthetic MnA-PtCu/C catalyst increases by 90% relative to commercial Pt/C catalyst. As a result of the increase in active areas and the additional promotion effects by Cu, the MnA-PtCu/C catalyst reveals a methanol oxidation activity 1.7 and 4.0 times higher than that of the synthetic PtCu/C and commercial Pt/C catalysts, respectively.

Increasing energy demands led us to explore cheap, sustainable and efficient materials for energy conversion and storage, but limited strategies have been established to prepare nanoscale carbon materials with tunable nanostructures. In this work, a large-scale nano-sandwich (porous carbon/graphene/porous carbon) N-doped carbon material was synthesized by in situ carbonization of glucose with small amounts of graphene oxide (GO), followed by activation with NH3. The resulting nano-sandwich N-doped carbon materials (NNCMs) possess variable nano-pores (0.8–5 nm) and high surface area (808–1959 m2 g−1), as well as nitrogen moieties (1.87–4.63 at%), which can be well tuned by the route conditions. The optimum NNCM-1050-70 exhibited excellent ORR performance with a high onset potential (0.26 V vs. Ag/AgCl) and a large limiting current density (4.1 mA cm−2 at 0.6 V vs. Ag/AgCl); in neutral conditions the obtained maximum power density (985.3 mW m−2) was higher than that of commercial Pt/C catalysts (874.3 mW m−2). When used as electrode materials for supercapacitors, the optimum NNCM-900-70 demonstrated remarkable performance with a specific capacitance of 178 F g−1 at a current density of 1 A g−1 in 6 mol L−1 KOH solution. Moreover, the NNCM-1050-70 also shows excellent performance of H2 and C2H2 adsorption compared to the best carbon materials. The excellent performance coupled with a scalable, facile and green method lead us to synthesize multifunctional carbon nanomaterials for energy conversion and storage.

Sandwich-type porous carbon/sulfur/polyaniline (SPC–S–PANI) composite with active sulfur nanoparticles confined within porous carbon is prepared. As a cathode material for Li–S batteries, the SPC–S–PANI composite with over 60 wt% sulfur content delivers high reversible capacity up to 1335 mA h g−1 for the first cycle and 834 mA h g−1 maintained over 100 cycles at 0.1C with an high coulombic efficiency of 96.5%. The high performance is attributed to the rationally designed hierarchical structure, which resulted in increased electrical conductivity, and hampered the dissolution of lithium polysulfide and provided a large pore volume for sulfur impregnation. Based on these merits, this sandwich-type porous carbon/polyaniline sulfur cathode shows the great potential for application in high-performance lithium–sulfur batteries.

The development of efficient oxygen reduction reaction (ORR) electrocatalysts composed of low cost and earth abundant elements is imperative for several energy systems. It has been reported that metal-free co-doped materials play a key role in the oxygen reduction reactions. However, a Si/F co-doped material has never been considered as an electrocatalyst for the ORR. Herein, we report a Si–C–F decorated three-dimensional porous carbon material by a facile pyrolysis of a mixture of D-glucose, ammonium fluoride and SiO2 nanoparticles in an argon atmosphere. It shows an excellent electrocatalytic performance with an onset potential of E = 0.24 V and a limiting current density of I = 4.5 mA cm−2 which is better than that of traditional electrocatalysts under neutral conditions. This outstanding electrocatalytic performance is due to the synergistic effect of silicon and fluorine which causes a change in the charge distribution and energetic characteristics of the Si–C–F decorated porous carbon material. For the practical application, a microbial fuel cell equipped with this electrocatalyst as the cathode reveals a high maximum power output and open circuit voltage (1026 mW m−2 and 780 mV), which are higher than those of commercial 20% Pt/C catalysts (913 mW m−2 and 750 mV).

In this paper, RuO 2 -SnO 2 binary oxides were prepared using a hydrothermal approach and added to Vulcan XC-72 carbon black as new support material for Pd. The X-ray diffraction, Transmission electron microscopy and X-ray photoelectronic spectra results show that the addition of binary oxides leads to the formation of (Ru,Sn)O 2 solid solution in Pd/C catalyst and reduces the particle size of Pd particles due to the anchoring effect. In addition, the electrochemical CO-striping measurement reveals that the Pd/RuO 2 -SnO 2 /C catalyst exhibits the largest electrochemical active surface and the best CO tolerance. Moreover, cyclic voltammetry and chronoamperometry tests demonstrate that the Pd/RuO 2 -SnO 2 /C catalyst possesses a much higher specific activity (4.4 mA cm −2 ) than that of the Pd/C catalyst (3.2 mA cm −2 ) towards ethylene glycol electrooxidation in alkaline media, and better stability as well. These results support the suitability of Pd/RuO 2 -SnO 2 /C catalyst developed in this work as a promising candidate for direct alcohol fuel cells (DAFCs) application.

A series of novel nanoarchitectures of SnO2@rGO–carbon inserted with carbon nanoparticles of BP2000 and KJ600 was successfully prepared by a facile coprecipitation method. TGA, XRD, SEM, TEM and Raman spectrom analysis are carried out and indicate that SnO2 nanoparticles and carbon intermediates are uniformly dispersed on graphene nanosheets at a molecular level, forming the framework nanoarchitectures of SnO2@rGO–carbon particles. SnO2@rGO–BP2000 delivers a discharge capacity of 1284.4 mAhg−1 and 76% retention of the reversible capacities after 60 cycles at an initial current density of 100 mAg−1. SnO2@rGO–BP2000 also showed the best rate performance among three anode materials at both high and low rate. The outstanding performance of the SnO2@rGO–BP2000 is attributed to well-defined morphology with suitable particle size, uniform distribution as well as enough room for the SnO2 volume expansion based on the graphene–carbon particles framework.

In this paper, CaSiO 3 was prepared using a thermal decomposition approach and added to Vulcan XC-72 carbon black as support material. The X-ray diffraction and Transmission electron microscopy results show that the addition of CaSiO 3 does not significantly change the particle size and distribution of Pd nanoparticles. The X-ray photoelectron spectroscopy reveals the interaction between Pd and CaSiO 3 . In addition, the electrochemical CO-striping measurement reveals that the Pd/50CaSiO 3 /C catalyst exhibits the largest electrochemical active surface and best CO tolerance. Moreover, cyclic voltammetry and chronoamperometry tests demonstrate that the Pd supported by CaSiO 3 and C (50:50 in wt.%) possesses a much higher current density (1408 mA mg −1 ) than that of the Pd/C catalyst (743 mA mg −1 ) towards ethanol oxidation in alkaline media, and better stability as well. These results support the suitability of Pd/50CaSiO 3 /C catalyst developed in this work as a promising candidate for direct ethanol fuel cells application

In this work, a series of palladium and palladium-lead nanoparticles supported on active carbon, graphene and nitrogen-doped graphene are synthesized via a one-step reduction method. Atomic absorption spectroscopy, X-ray powder diffraction, transmission electron microscope and X-ray photoelectron spectroscopy are used to characterize the catalysts. The results indicate that metal nanoparticles are more uniformly dispersed on the surface of N-doped graphene than those on graphene, without any aggregation. Various electrochemical techniques are carried out to evaluate the electrocatalytic ethanol oxidation activity and durability. The peak current for ethanol electrooxidation of Pd/N-doped graphene increases to 70.2 mA cm−2, obviously higher than that of Pd/Graphene (38.0 mA cm−2) and even surpasses that of Pd/C (51.9 mA cm−2). N-doped graphene support not only possesses faster dehydrogenation but provides an electron effect to Pd. Introduction of Pb into the catalyst causes the formation of abundant oxygenated species on the catalyst surface at low potential. Based on the synergistic effect of N and Pb towards Pd particles, the PdPb/N-doped graphene catalyst (Pd:Pb = 8:1.0) exhibits remarkably enhanced activity up to 152.3 mA cm−2 for ethanol oxidation, which is 4.0 and 2.9 times higher than that of Pd/Graphene and Pd/C, respectively. The catalytic durability and stability are also greatly improved.

Nitrogen and fluorine co-doped carbon black (BP-NF) was prepared via the direct pyrolysis of a mixture of polytetrafluoroethylene (PTFE) and BP-2000 under an ammonium atmosphere for high efficient ORR electrocatalysis in the air-cathode of microbial fuel cells (MFCs). The electrocatalytic activity of BP-NF is higher than that of single nitrogen or fluorine doped carbon materials (BP-N, BP-F), with an onset potential of E = 0.2 V (BP-NF), E = 0.1 V (BP-N), and a limiting current density of I = 4.5 mA cm−2 (BP-NF), I = 0.31 mA cm−2 (BP-F), respectively. The results demonstrated a synergistic ORR catalytic effect in N and F co-doping carbon material. The maximum power density of MFC with BP-NF as the cathode catalyst (672 mA cm−2) was higher than that with commercial Pt/C (572 mA cm−2).