High pressure pyrolyzed non-precious metal oxygen reduction catalysts for alkaline polymer electrolyte membrane fuel cells

Non-precious metal catalysts, such as metal-coordinated to nitrogen doped-carbon, have shown reasonable oxygen reduction reaction (ORR) performances in alkaline fuel cells. In this report, we present the development of a highly active, stable and low-cost non-precious metal ORR catalyst by direct synthesis under autogenic-pressure conditions. Transmission electron microscopy studies show highly porous Fe-N-C and Co-N-C structures, which were further confirmed by Brunauer-Emmett-Teller surface area measurements. The surface areas of the Fe-N-C and Co-N-C catalysts were found to be 377.5 and 369.3 m2 g-1, respectively. XPS results show the possible existence of N-C and M-Nx structures, which are generally proposed to be the active sites in non-precious metal catalysts. The Fe-N-C electrocatalyst exhibits an ORR half-wave potential 20 mV higher than the reference Pt/C catalyst. The cycling durability test for Fe-N-C over 5000 cycles shows that the half-wave potential lost only 4 mV, whereas the half-wave potential of the Pt/C catalyst lost about 50 mV. The Fe-N-C catalyst exhibited an improved activity and stability compared to the reference Pt/C catalyst and it possesses a direct 4-electron transfer pathway for the ORR process. Further, the Fe-N-C catalyst produces extremely low HO2- content, as confirmed by the rotating ring-disk electrode measurements. In the alkaline fuel single cell tests, maximum power densities of 75 and 80 mW cm-2 were observed for the Fe-N-C and Pt/C cathodes, respectively. Durability studies (100 h) showed that decay of the fuel cell current was more prominent for the Pt/C cathode catalyst compared to the Fe-N-C cathode catalyst. Therefore, the Fe-N-C catalyst appears to be a promising new class of non-precious metal catalysts prepared by an autogenic synthetic method. © The Royal Society of Chemistry 2015.

Development of Novel Non-precious Cathode Electrocatalysts for Alkaline Exchange Membrane Fuel Cells

DoctordCollectio

Prussian Blue-Carbon Hybrid as a Non-Precious Electrocatalyst for the Oxygen Reduction Reaction in Alkaline Medium

We describe a simple approach for the Prussian blue nanocubes dispersed on carbon composite (PBC/C) as a non-precious catalyst for the electrochemical oxygen reduction reaction (ORR) in alkaline medium. The interaction between Prussian blue (PB) and the carbon support was confirmed by using FT-IR, and XPS spectroscopy. PBC/C catalyst exhibits 100 mV more positive onset potential than Prussian blue supported on carbon (PB/VXC-72) for ORR. Rotating disk electrode measurements showed that PBC/C had about 17 times higher oxygen reduction mass activity compared to the PB/VXC-72 physical mixture. PBC/C hybrid catalyst exhibited superior durability in aqueous alkaline medium compared with Pt/C and also provided low H2O2production confirmed by rotating ring-disk electrode measurement. The PBC/C catalyst showed better activity and selectivity, which can be attributed to the synergistic coupling effects between the PB nanocubes and carbon support. © 2013 Elsevier Ltd.

Boron and phosphorous-doped graphene as a metal-free electrocatalyst for the oxygen reduction reaction in alkaline medium

An efficient solid-state pyrolysis route is presented to prepare boron- and phosphorous-doped graphene without using a template, solvent, or catalyst. By controlling the pyrolysis temperature, selective doping of phosphorous or boron was achieved. Phosphorous-doped graphene (PDG) and boron-doped graphene (BDG) samples are obtained when pyrolysing the precursor at 700°C and at 900°C, respectively under autogenic pressure. PDG and BDG electrodes show a considerable oxygen reduction activity by a direct four-electron pathway in alkaline medium. Further, these catalysts show improved durability under continuous oxygen reduction, resistance to methanol oxidation and CO-tolerance than the commercial catalyst. The results suggest that by tuning the reaction temperature, selective doping of either boron or phosphorous in graphene was achieved and the doped graphene samples were used as non-precious and metal-free catalysts for oxygen reduction. © The Royal Society of Chemistry.1

Polyoxometalate decorated graphene oxide/sulfonated poly(arylene ether ketone) block copolymer composite membrane for proton exchange membrane fuel cell operating under low relative humidity

A phosphotungstic acid (PW) decorated graphene oxide (GO) is explored as a filler for sulfonated poly(arylene ether ketone) (SPAEK) block copolymer. The SPAEK/PW-mGO composite membrane shows higher proton conductivity than a pristine SPAEK membrane. At 80 °C under 25% relative humidity (RH) condition, the fuel cell configured with the SPAEK/PW-mGO composite membrane shows improved fuel cell performance. A maximum power density of 772 mW cm−2 is observed for the SPAEK/PW-mGO composite membrane, whereas the pristine SPAEK membrane exhibits a maximum power density of 10 mW cm−2 operated under 25% RH at 80 °C. Compared with the NRE-212 membrane, the SPAEK/PW-mGO composite membrane exhibits 4.8-times higher maximum power density. Furthermore, the maximum current density of the SPAEK/PW-mGO composite membrane (2271 mA cm−2) is much higher than pristine SPAEK (39 mA cm−2) and NRE-212 (734 mA cm−2) membranes. © 2017 Elsevier B.V.1

Hollow nitrogen-doped carbon spheres as efficient and durable electrocatalysts for oxygen reduction

Hollow nitrogen-doped carbon spheres (HNCSs) were prepared by a facile method as non-precious catalysts for the oxygen reduction reaction (ORR). The HNCS catalysts exhibited ORR activity comparable with a commercial Pt/C catalyst and superior stability in alkaline electrolyte medium. This journal is © the Partner Organisations 2014.

Self-supported iron-doped nickel sulfide as efficient catalyst for electrochemical urea and hydrazine oxidation reactions

The electrochemical oxidation of urea and hydrazine over self-supported Fe-doped Ni3S2/NF (Fe–Ni3S2/NF) nanostructured material is presented. Among the various reaction conditions Fe–Ni3S2/NF-2 prepared at 160 °C for 8 h using 0.03 mM Fe(NO3)3 shows the best results for the hydrazine and urea oxidation reactions. The potential values of 0.36, 1.39, and 1.59 V are required to achieve the current density of the 100 mA cm−2 in 1 M hydrazine (Hz), 0.33 M urea, and 1 M KOH electrolyte, respectively. The onset potential in 1 M KOH, 0.33 M Urea +1 M KOH, and 1 M Hz + 1 M KOH values are 1.528, 1.306, and 0.176 respectively. The Fe–Ni3S2/NF-2 shows stable performance at 10 mA cm−2 until 50 h and at 60 mA cm−2 over the 25 h. A cell of PtC//Fe–Ni3S2/NF-2 requires the potential of 0.49, 1.46, and 1.59 V for the hydrogen production in 1 M Hz + 1 M KOH, 0.33 M Urea +1 M KOH, and 1 M KOH electrolyte, respectively, at a current density of 10 mA cm−2, and almost 90% stable for the hydrogen production over the 80 h in all electrolytes. The improvement of the chemical kinetics of urea and hydrazine oxidation is due to the synergistic effect of the adsorption and fast electron transfer reaction on Fe–Ni3S2/NF-2. The doped Fe ion facilitates the fast electron transfer and the surface of Ni3S2 support to the urea and hydrazine molecule adsorption. © 2022 Hydrogen Energy Publications LLCFALS

Hierarchical Nanostructured Pt8Ti-TiO2/C as an Efficient and Durable Anode Catalyst for Direct Methanol Fuel Cells

A catalyst for the electrochemical oxidation of methanol in direct methanol fuel cells (DMFCs) comprising Pt8Ti intermetallic nanoparticles dispersed in carbon nanorods (Pt8Ti-TiO2/C) is presented. The catalyst consists of Pt8Ti and rutile TiO2 nanoparticles dispersed in nitrogen-doped carbon hierarchical nanostructures. The Pt8Ti-TiO2/C catalyst showed a 50 mV positive onset potential and 10 times higher specific activity than a commercial Pt/C catalyst. Using a half-cell experiment, we show that Pt8Ti intermetallic nanoparticles greatly enhance the methanol oxidation activity and durability in comparison to a Pt/C commercial catalyst. More importantly, a DMFC anode constructed with Pt8Ti-TiO2/C catalyst showed 4.6 times higher power density than a commercial Pt/C catalyst at 0.35 V and 333 K. Additionally, the Pt8Ti-TiO2/C catalyst displayed superior durability in comparison to the Pt/C catalyst. Pt8Ti-TiO2/C showed an electrochemical surface area decay of 23% at the end of 3000 CV cycles, whereas the Pt/C catalyst showed a more rapid decay of 90% at the end of 3000 CV cycles. The excellent stability of the Pt8Ti-TiO2/C catalyst during the accelerated durability stability test (AST) can be attributed to the stability of the rutile TiO2 support, which is chemically resistant in the acidic electrolyte medium. The chronoamperometry and AST durability results confirmed that the Pt8Ti-TiO2/C hierarchical catalyst exhibited better stability than the pure Pt/C catalyst, suggesting that Pt8Ti-TiO2/C could be a promising anode catalyst in DMFCs. © 2015 American Chemical Society.

In-situ growth of nitrogen-doped mesoporous carbon nanostructure supported nickel metal nanoparticles for oxygen evolution reaction in an alkaline electrolyte

Rational three-dimensional nitrogen doped mesoporous carbon nanostructured surfaced Nickel metal (Ni) nanoparticles (nps), NCNP composites have been developed using nickel organic complex and utilized as an electrocatalyst for oxygen evolution reaction. The NCNP composites of tunable physio-chemical characteristics, such as Ni nps size (∼18–∼42 nm), surface area (∼18–∼43 m 2 g −1 ), pore size (3.23–3.84 nm) and nitrogen doping amount (1.20–3.87 wt%) have been achieved via controlled carbonization temperature. An optimized NCNP composite of favorable physio-chemical properties has delivered good oxygen evolution kinetics such as a lower overpotential value (370 mV) at 10 mA cm −2 , a minimum Tafel slope value (55 mV dec −1 ), and relatively a higher electrochemical surface area (0.6325 cm −2 ) than the other NCNP composites. Moreover, the best NCNP electrocatalyst has shown a comparable overpotential value with the benchmarking catalyst at 10 mA cm −2 , equivalent to ∼10% solar photoelectrical conversion efficiency. In addition, the best NCNP electrocatalyst has exhibited excellent accelerated degradation test for 24 h at a constant current density of 10 mA cm −2 with an increase overpotential value of 0.029 V. © 20191