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In order to obtain the catalyst with Pt isolated-atom surface and high performance towards formic acid electro-oxidation (FAEO), cyclic potential dealloying method was employed for preparing dealloyed PtCu/C (D-PtCu/C) catalysts, and the effect of dealloying parameters on the activity of D-PtCu/C catalysts also were investigated. XRD results show that both of PtCu and D-PtCu catalysts are face-centered cubic (fcc) structure. TEM, XPS and ICP results demonstrate the dissolution of Cu atoms and the formation of core-shell structure. And HRTEM results further exhibit the etched surface of D-PtCu/C catalyst which should be made up of isolated atom and atomic clusters of Pt. By electro-chemical analysis, the performance towards FAEO is extremely enhanced. The onset potential of FAEO on D-PtCu/C is at − 0.1 V (vs. SCE) and only one peak is confirmed at 0.5 V which negatively shifts about 0.19 V compared with the peak of commercial Pt/C (at 0.69 V). The mass activity of optimized D-PtCu/C reaches up to 1253.89 mA mg− 1 Pt at 0.5 V, which is 6.20 times as high as that of Pt/C (202.40 mA mg− 1 Pt). And the specific activity (2.36 mA cm− 2) is 8.43 times of Pt/C (0.28 mA cm− 2). The increased activity should be ascribed to the electronic effect and ensemble effect, which reduce the chemisorption of CO and promote the dehydrogenation process.

A novel sulfonated poly(ether ether ketone) (SPEEK)/TiO2 double-deck membrane which consists of a layer of SPEEK and a layer of TiO2 was prepared and investigated for vanadium redox flow battery (VRB) application for the first time. The physicochemical properties of the SPEEK/TiO2 membrane, including the water uptake, swelling ratio, ion exchange capacity, proton conductivity, VO2 + permeability and ion selectivity are evaluated in detail, compared to the pristine SPEEK membrane and Nafion 117 membrane. The scanning electron microscopy images reveal its double-deck structure and the structural stability with no delamination, and thermogravimetric analysis (TG) identifies its thermal stability. Among all membranes, the SPEEK/TiO2 double-deck membrane possesses lowest vanadium ion permeability (6.66 × 10− 7 cm2 min− 1) and highest ion selectivity (9.46 × 104 S min cm− 3). The VRB single cell with SPEEK/TiO2 double-deck membrane shows higher coulombic efficiency (97.0% vs 93.3%) and energy efficiency (85.8% vs 83.7%) compared to that with Nafion 117 membrane at 60 mA cm− 2. Furthermore, the SPEEK/TiO2 double-deck membrane exhibits highly stable cell performance after 60 times of cycling tests at 60 mA cm− 2 and lower capacity decay rate than that of Nafion 117 membrane. Therefore, the SPEEK/TiO2 double-deck membrane exhibits good potential usage in VRB systems.

Several organic amines with –NH2 functional groups and inorganic ammoniums with –NH4+ functional groups have been comparatively investigated as stabilizers of the V(V) electrolyte for vanadium redox flow battery (VRB) to improve its stability and electrochemical performance. Thermal stability tests showed that chitosan (CTS) and nonionic-type polyacrylamide (NPAM) additives with –NH2; ammonium thiocyanate (ATC), ferrous ammonium sulfate (FAS) and ammonium ferric sulfate (AFS) additives with –NH4+ could significantly improve the thermal stability of the V(V) electrolyte over a wide temperature range of − 5 °C to 45 °C. The electrochemical behavior of the V(V) electrolyte with these preferred additives was further studied by cyclic voltammetry (CV), steady state polarization, electrochemical impedance spectroscopy (EIS) and charge–discharge test. The results indicated that the electrochemical activity and reversibility for the V(V) electrolyte with the best additive CTS with –NH4+ was significantly improved compared with the additives with –NH2 and pristine one. In addition, the VRB employing the positive electrolyte with CTS exhibited excellent cycling stability and charge–discharge behavior with a high energy efficiency of 82.5%. The N-containing and O-containing functional groups of CTS in the V(V) electrolyte could modify the electrode and further improve the electrochemical performance and cycling stability of VRB.

A novel anode electrode consisting of Pt NPs on layered porous TiO2/CFP (Pt/LP-TiO2/CFP) was fabricated by an innovative approach, which can be directly integrated in membrane electrode assembly (MEA) as the catalyst layer without any binder. Firstly, a two-step anodization method was applied to prepare a layered porous TiO2 on the CFP as a hybrid support, and then Pt NPs are deposited onto it by atomic layer deposition (ALD) technology. It effectively prevents Pt nanoparticles from detachment, migration, and aggregation during the catalyst preparation and electrochemical reaction process. The electrocatalytic performance of Pt/LP-TiO2/CFP electrode for methanol oxidation reaction exhibits excellent mass activity (1182.8 mA mgPt−1), enhanced stability, and CO tolerance, which is much better than those of the Pt/HT-TiO2/CFP and the Pt/C/CFP electrode prepared by conventional hydrothermal and spray method, respectively. The reason can be attributed to the unique structure of layered porous TiO2 supports, strong metal−support interactions (SMSI) between ALD Pt NPs and the LP-TiO2/CFP, and more exposed active sites for methanol oxidation. The presented ALD approach is an effective strategy for the homogeneous distribution of precious Pt nanoparticles on a binder-free and porous electrode for the design of advanced catalysts.

Development of earth-abundant materials as novel substitutes for platinum group metal catalysts towards the oxygen reduction reaction (ORR) remains a great challenge to drive the commercialization of fuel cell. Iron-based catalysts were synthesized by using a metal-organic framework (MOF) as the precursor. FeNC-650, which is obtained by pyrolyzed at 650 °C, is composed of Fe and Fe3O4 nanoparticles encapsulated in the nitrogen-enriched mesoporous carbon. It exhibits higher electrocatalytic activity and stability, compared with other FeNC catalysts and commercial Pt/C for ORR. The effect of pyrolysis temperature on active sites and unique structures is investigated. The excellent electrocatalytic performance and superior stability make it a promising non-precious metal catalyst for practical fuel cell application.

Several compounds have been employed as additives of the V(V) electrolyte for vanadium redox flow battery (VRB) to improve its stability and electrochemical activity. Stability of the V(V) electrolyte with and without additives was investigated with ex-situ heating/cooling treatment over a wide temperature range of −5 °C to 60 °C. It was observed that methyl orange (MO), Triton X-100 (OP), sodium ligninsulfonate (SL), sodium dodecyl sulfate (SDS) and polyvinyl alcohol (PVA) could significantly improve the stability of the V(V) electrolyte at a wide range of temperature. Their electrochemical behavior in the V(V) electrolyte were further studied by cyclic voltammetry (CV), steady state polarization and electrochemical impedance spectroscopy (EIS). The results showed that the electrochemical activity, including the reversibility of electrode reaction, the diffusivity and polarization resistance of V(V) species and the feasibility of charge transfer of V(V)/V(IV) for the V(V) electrolyte with these additives was all improved compared with the pristine solution.