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Sunken hollow carbon spheres (SHCs) are prepared by using glucose as carbon source and polystyrene spheres (PSs) as templates. Pt particles are then loaded on the SHCs as electrocatalyst and used for catalyzing both methanol oxidation and oxygen reduction reaction (ORR) in acidic media. Physical measurements show that the SHCs are formed due to sinking of hollow carbon spheres. It can be imagined that the SHCs have the similar specific surface area as hollow carbon spheres with reduced volume. Moreover, the SHCs have high surface area (786.3 m² ⋅ g^-1) with hollow and sunken structure are beneficial for the uniform dispersion of the noble metal particles and efficiently improve the mass transfer in catalytic reactions. The cyclic voltammogram measurements show that the current densities on Pt/SHC electrocatalyst are 2.1 times ) that on commercial Pt/C for methanol oxidation and 1.5 times () that on Pt/C for ORR at the same Pt loadings, being promising candidate for fuel cell electrocatalyst.

Enhancing oxygen reduction reaction (ORR) activity and simultaneously reducing usage of noble metal catalysts are significantly important both in fundamental and applied science communities for polymer electrolyte fuel cells (PEFCs). In this work, we confirm the proton conductor (perfluorosulfonic acid, containing $-$SO₃H) can promote the specific activity $(I_{\text{s}})$ of metal catalysts toward ORR. Herein, Pt nanoparticles (NPs) with a small and narrow size distribution are encapsulated with perfluorosulfonic acid through a simple colloidal route. The resulting catalyst obtains about two times $(I_{\text{s}})$ towards ORR than that of the pristine Pt/C. Significantly, the amount of $-$SO₃H groups is controlled by a heat-treatment method to investigate the influence of $-$SO₃H groups on $(I_{\text{s}})$. The results evidence the contribution of $-$SO₃H groups to elevating the ORR specific activity. The mechanism can be ascribed to the $-$SO₃H groups which effectively promote the transfer process of reaction species (e.g., H${}^{+}$, H₂O), improving the triple-phase boundary (TPB).

In this study, we report the findings that the C–N composites containing Ni and Co (Ni₁Co₁/C–N, Ni₃Co₁/C–N, Ni₆Co₁/C–N, Ni₉Co₁/C–N, Ni${}_{10}$Co₀/C–N and Ni₀Co${}_{10}$/C–N) can be produced by direct pyrolysis of the NiCo-doped polyaniline (PANI) precursors in N₂ atmosphere at 800${}^{\circ }$C and show efficient electroactivity for oxygen reduction reaction (ORR) in alkaline media. Distribution and compositions of the catalysts were characterized by SEM, TEM, EDS and XRD techniques. The catalysts were loaded on carbon paper to prepare gas diffusion electrodes, in which electrocatalytic activity for ORR in alkaline media was investigated by voltammetric techniques. The ORR current density on these carbon paper-supported NiCo/C–N catalysts exhibits a linear increase with the negative shift of ORR potential. The ORR onset potential is around $-$0.2V (versus Ag/AgCl) in alkaline media. Among the prepared catalysts, the catalyst Ni₆Co₁/C–N presents the largest ORR current density, which is 68.5mAcm${}^{-2}$@$-$0.8V (versus Ag/AgCl) in alkaline media. Moreover, Ni₆Co₁/C–N catalyst also presents good electrocatalytic activity stability for ORR.

Cobalt phosphide (CoP) has aroused extensive research interest in a field of electrochemical application due to its excellent catalytic activities. CoP and its compounds have been widely reported using in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). However, few reports about CoP as electrocatalysts for oxygen reduction reaction (ORR) were presented. In this work, we prepare reduced graphene-oxide(rGO)-loaded CoP (rGO@CoP) as an electrocatalyst for ORR through in situ hydrothermal treatment. The rGO@CoP as ORR catalyst exhibits excellent activities where its onset potential has a positive increase of 129mV, and the ORR potential achieves an increase of 330mV at a current density of 1.0mAcm${}^{-2}$ compared with that of pure CoP. The current density is also significantly improved with an increase of 0.51mAcm${}^{-2}$ at $-$350mV, and the Tafel slope has a decrease of 19mV dec${}^{-1}$. Further tests show that the electron transfer number of rGO@CoP is 3.66, which is larger than 2.19 of pure CoP, indicating that it is dominated by a four-electron transfer pathway. Moreover, its stability (remained 98.6% current after working 6000s) and methanol tolerance are outstanding. These results show that rGO@CoP may be considered to replace traditional Pt-based ORR catalysts for fuel cells, and rGO loading has been proven to be an effective strategy to enhance the ORR performance of CoP, which may provide a new idea to synthesize transition metal phosphides as ORR catalysts.

Improving the efficiency of glucose oxidation reaction (GOR) is extremely important to build high performance nonenzymatic glucose sensors and fuel cells. In this work, we designed a novel binary ($\alpha$–$\beta )$ NiS/PANI nanorods electrocatalyst with polyaniline (PANI) as the substrates and binary ($\alpha$–$\beta )$ NiS nanoparticles dispersing on the PANI nanorods. The as-prepared NiS/PANI nanorods were characterized by XRD, XPS and SEM. The electrochemical performance of NiS/PANI nanorods was evaluated by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy, which showed highly improved catalytic efficiency for GOR. When used as anodic catalysts in nonenzymatic glucose fuel cells, NiS/PANI nanorods displayed much higher power density of 1343.39 $\mu \mathrm{\text{W}}\cdot {\mathrm{\text{cm}}}^{-2}$ with an open circuit voltage of 0.84 V. NiS/PANI/NiS nanorods also presented excellent nonenzymatic sensing performance for glucose detection including a wide sensitivity of 682.21 $\mu \mathrm{\text{A}}\cdot {\mathrm{\text{mM}}}^{-1}\cdot {\mathrm{\text{cm}}}^{-2}$ (10–9000 $\mu$M) and the low detection limit of 3.33 $\mu$M ($\mathrm{\text{S/N}}=3$). The obviously improved electrochemical properties of NiS/PANI/NiS nanorods for GOR may be due to the synergistic effect of binary ($\alpha$–$\beta )$ NiS and PANI nanorods.

Direct oxidation of tryptophan on multi-wall carbon nanotubes modified glassy carbon electrode was examined. Surface poisoning, which was suppression of oxidative current caused from adsorption of oxidized compounds of amino acids through multiple redox scan, was observed on carbon material electrodes (multi-wall carbon nano tube(CNT), carbon powder(CP), Ketjen Black (KB) and glassy carbon(GC). It was found that CNT showed a highly inhibitory effect on the surface poisoning and high current value in the direct oxidation of tryptophan because of a π-π interaction between CNT and indole ring of tryptophan results from orbital mixing. This CNT modified GC electrode was applied to an anode in a fuel cell used with amino acids as fuel. As a result, the maximum of the power density showed 0.36 mW cm^-2 at 2.5 mA cm^-2 of the current density and 140 mV of the cell voltage.