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Novel nitrogen-functionalized multimodal porous graphite felt (GF) electrodes for all-vanadium redox flow batteries (VRFB) have been developed using a simple binder-free fabrication method. We synergistically combined a polymer of intrinsic microporosity (PIM), as a carbon and nitrogen precursor, with vapor-induced phase separation. The GF with a carbonized PIM skin layer showed a high surface area and multimodal pore architecture featuring interconnected micro-, meso-, and macropores. The enhanced electrochemical reactivity and wettability , and excellent electronic conductivity of the prepared electrodes successfully improved the overall kinetics of the redox reactions of the vanadium ion species by providing highly active catalytic sites and efficient ion and electron transport pathways. This resulted in the outstanding performance of VRFB single cells using this material as electrodes.

We develop a novel approach to improve the robustness of the interface between the hydrocarbon (HC) membrane and the perfluorosulfonic acid (PFSA) ionomer-based catalyst layer (CL) in membrane electrode assemblies (MEAs). This approach involves the creation of a gradient-composition interfacial bonding layer, in which the HC and PFSA contents are gradually varied along the thickness direction. The layer is fabricated using a simple spray-coating method, in which HC and PFSA ionomer mixtures with different compositions are sprayed stepwise onto both sides of the HC membrane surface. The interfacial structure developed in this process minimizes the chemical incompatibility between the HC and PFSA polymers. Owing to the tightly bound sublayers resulting from the intertwined HC and PFSA microdomains, the gradient-composition bonding layer provides a significantly improved interfacial adhesion strength (14 times higher than that of the pristine membrane without bonding layer) between the HC membrane and the PFSA-based CL. Finally, the fabricated MEA exhibits a >433% higher durability in humidity cycling tests compared with the pristine MEA without interfacial bonding layer, together with a better retention of its initial performance.

Novel nitrogen-doped CNT-containing graphite felt (N-CNT/GF) hybrid electrodes with high electrocatalytic activity were developed for all-vanadium redox flow batteries (VRFBs). A simple, effective preparation method for N-CNT/GFs using metal (Fe, Co, and Ni) phthalocyanines as the carbon and nitrogen precursor is presented. We found that different metal precursors generated different densities of N-CNTs on the surface of the GFs due to the various interactions of the metals (Fe, Co, Ni) with the carbon precursor during carbonization. Higher density and longer N-CNTs were obtained for N-CNT/GF (Fe), which gave rise to a higher N-doping concentration, enhanced wettability and conductivity, and improved electrochemical reactivity. When used as an electrode in a VRFB single cell, this material showed outstanding performance with an increase in energy efficiency of more than 20% compared to pure GF at a high current density (150 mA/cm2).

Bio-inspired non-precious-metal catalysts based on iron and cobalt porphyrins are promising alternatives to replace costly platinum-based catalysts for oxygen reduction reaction (ORR) in fuel cells. However, the exact nature of the active sites is still not clearly understood, and further optimization design is needed for practical applications. Here, we report a rational catalyst design process by combining density functional theory (DFT) calculations and experimental validations. Two sets of square-planar (MNxC4−x) and square-pyramid (MNxC5−x) active centers (M=Mn, Fe, Co, Ni) incorporated in graphene were examined using DFT. Fe-N5 and Co-N4 sites were identified theoretically to have the best performance in fuel cells, while Ni-NxC4−x sites catalyze the most H2O2 byproduct. Graphene samples with well-dispersed incorporations of metals were synthesized, and the following electrochemical measurements show an excellent agreement with the theoretical predictions, indicating that a successful design framework and systematic understanding toward the catalytic nature of these materials are established.

There are many studies portraying iron (Fe) and nitrogen (N)-functionalzed carbon as an electrocatalyst along with possible elucidation of catalytically active sites. Despite continuous controversial debate on the active sites/species, the presence of N is believed to be undeniably needed for the efficient catalysis, whereas the necessity and role of Fe are still debated. To clearly understand the role of Fe in Fe and N-functionalized electrocatalyst, N-doped hollow mesoporous shell carbon (N-HMSC) is prepared as a uniform model electrocatalyst by a simple template nanocasting using Fe phthalocyanine (FePc) as a single precursor for carbon, N, and Fe. It is found that the presence of Fe in N-HMSC leads to the efficient graphitization of N-HMSC structure, which can be beneficial for electrocatalytic oxygen evolution reaction (OER). Interestingly, it is observed that Fe is a must for the preparation of high efficient catalyst, but may not be necessary for OER.

Platinum-free electrocatalysts especially, various heteroatom-doped carbon nanostructures have attracted particular attraction as plausible solution for commercializing fuel cell technology. In this direction, novel phosphorus-doped platelet ordered mesoporous carbon (P-pOMC) is developed for the first time as metal-free electrocatalyst for alkaline oxygen reduction reaction. The P-pOMC is synthesized by nanocasting method using platelet ordered mesoporous silica as template. Various characterizations reveal that the P-pOMC materials have covalently bound P atoms with carbon framework for facilitation of oxygen reduction reaction (ORR) and also have very high surface area with uniform distribution of short mesoporous channels for unhindered mass transfer. Combination of P doping and excellent surface properties empowers the newly-developed P-pOMC catalyst to show high ORR activity nearly equal to that of state of the art Pt catalyst along with superior long-term stability and excellent methanol tolerance.

A simple, efficient and scalable approach is developed for synthesis of Vulcan XC-72(carbon)-supported Pt nanoparticles (NPs) that combines homogeneous deposition (HD) of Pt complex species through reaction with OH - ions generated by in situ hydrolysis of urea and subsequent reduction by reducing species generated from radiolysis of water by γ-rays. This method not only avoids addition of any commonly used reducing agent, but also offers more uniform homogeneous dispersion of Pt NPs with much smaller particle size. Thus, when used as a cathode catalyst for proton exchange membrane fuel cell, the synthesized carbon-supported Pt NPs demonstrate excellent oxygen reduction electro–catalytic activity, higher Pt utilization efficiency, and considerably improved fuel cell polarization performance compared to those of Pt catalysts prepared with other synthesis strategies such as conventional NaBH 4 reduction and HD-ethylene glycol method as well as commercial Pt catalyst. The combined HD-γ-irradiation strategy is found to be simple, reproducible and efficient with mild synthesis condition and in particular, holds great promises for large scale production of highly efficient Pt-based catalysts for fuel cells.

Platinum counter electrodes in DSSC are generally prepared by thermal reduction method. Poor control over Pt particle size, agglomeration and bad adhesion to the transparent conducting substrate, are some of the shortcomings affecting overall efficiency of the cell. In order to achieve better dispersion and control over the particle size, we explored direct deposition of metal nanoparticles (NPs) from their precursor solution onto the FTO glass substrate by using a simple and effective urea-assisted homogenous deposition (HD) method. This method works at substantially lower temperature for hydrolysis of urea and uses mild reducing agent, ethylene glycol (EG), giving better control over particle size along with better adhesion and negligible agglomeration compared to the thermal reduction method. DSSC prepared from such Pt counter electrode exhibited much enhanced photovoltaic performance compared to ones prepared by thermal and EG reduction alone, with better light-to-electricity conversion efficiency of 9.34% under one sun illumination. This excellent conversion efficiency is attributed to the uniform dispersion and smaller size of the Pt NPs prepared by the novel, combined urea-assisted HD–EG synthesis method.

A simple and efficient approach has been developed for the synthesis of carbon-supported binary PtFe (50:50) electrocatalyst with high metal loading that combines homogeneous deposition (HD) of PtFe hydroxide complex species through generation of OH− ions realized by in situ hydrolysis of urea and subsequent uniform reduction of the complex by ethylene glycol (EG) in a polyol process, providing control over the size and dispersion of PtFe nanoparticles (NPs). Compared to PtFe catalysts prepared with other common synthesis methods using NaBH4 and EG and commercial PtFe catalyst, the supported PtFe catalyst prepared by the HD-EG method reveals more uniform homogenous dispersion of PtFe NPs with much smaller particle size, thus demonstrating excellent electrocatalytic ability and fuel cell performance. The structural properties and catalytic activities of Pt–Fe catalysts prepared in various synthesis methods were evaluated on the basis of the analysis of HR-TEM, HR-SEM, XRD, electrochemical surface area and fuel cell polarization performance.

Pt–M@FP-MWNT catalysts (M = Ru, Ni, Co, Sn, and Au) were prepared by one-step γ-ray irradiation. Two different types of functional polymers (FP), such as poly(vinylphenyl boronic acid) (PVPBAc) and poly(vinylpyrorridone) (PVP), were used as anchoring agents, when Pt–M nanoparticles were deposited on the multi-walled carbon nanotube (MWNT) using γ-ray irradiation in aqueous solution at room temperature. The obtained Pt–M@FP-MWNT catalysts were then characterized by XRD, TEM, and elemental analysis. The catalytic efficiency of the Pt–M@FP-MWNT catalysts was examined for CO stripping and MeOH oxidation for use in a direct methanol fuel cell (DMFC). The catalytic efficiency of the Pt–M@FP-MWNT catalyst for MeOH oxidation follows this order: Pt–Sn@FP-MWNT > Pt–Co@FP-MWNT > Pt–Ru@FP-MWNT > Pt–Au@FP-MWNT > Pt–Ni@FP-MWNT catalysts. The CO adsorption capacity of the Pt–M@FP-MWNT catalyst for CO stripping is as follows: Pt–Ru@FP-MWNT > Pt–Sn@FP-MWNT > Pt–Au@FP-MWNT > Pt–Co@FP-MWNT > Pt–Ni@FP-MWNT catalyst.

This paper describes the functionalization of multi-walled carbon nanotubes (MWNTs) by radiation-induced graft polymerization (RIGP) of vinyl monomers with functional groups and the application of these MWNTs in enzyme-free biosensors. The vinyl monomers used were acrylic acid (AAc), methacrylic acid (MAc), glycidyl methacrylate (GMA), maleic anhydride (MAn), and 4-vinylphenylboronic acid (VPBAc). Tubular-type MWNTs were obtained via RIGP of various vinyl monomers. The poly(VPBAc)-grafted MWNTs (PVBAc- g -MWNTs) were used as sensing sites in enzyme-free glucose sensors for the detection of glucose without enzymes. The PVBAc- g -MWNTs electrode displayed an excellent linear response to glucose concentration in the range 1.0–10 mM. The functionalized MWNTs prepared by RIGP can be used as biosensor materials.