Porous Ni-Cu Alloy Dendrite Anode Catalysts with High Activity and Selectivity for Direct Borohydride Fuel Cells

Polypyrrole regulates Active Sites in Co-based Catalyst in Direct Borohydride Fuel Cells

Direct borohydride fuel cells (DBFCs) convert borohydride (NaBH4) chemical energy into clean electricity. However, catalytic active site deactivation in NaBH4 solution limits their performance and stability. We propose a strategy to regulate active sites in Co-based catalysts using polypyrrole modification (Co-PX catalyst) to enhance electrochemical borohydride oxidation reaction (eBOR). As an anode catalyst, the synthesized Co-PX catalyst exhibits excellent eBOR performance in DBFCs, with current density of 280 mA ⋅ cm-2 and power density of 151 mW ⋅ cm-2, nearly twice that of the unmodified catalyst. The Co-PX catalyst shows no degradation after 120-hour operation, unlike the rapidly degrading control. In-situ electrochemical attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIRS) and density functional theory (DFT) suggest that polypyrrole-modified carbon support regulate the charge distribution, increasing oxidation state and optimizing adsorption/desorption of intermediates. A possible reaction pathway is proposed. This work presents a promising strategy for efficient polymer-modulated catalysts in advanced DBFCs.

High Entropy Pr-Doped Hollow NiFeP Nanoflowers Inlaid on N-rGO for Efficient and Durable Electrodes for Lithium-Ion Batteries and Direct Borohydride Fuel Cells

The selection and design of new electrode materials for energy conversion and storage are critical for improved performance, cost reduction, and mass manufacturing. A bifunctional anode with high catalytic activity and extended cycle stability is crucial for rechargeable lithium-ion batteries and direct borohydride fuel cells. Herein, a high entropy novel three-dimensional structured electrode with Pr-doped hollow NiFeP nanoflowers inlaid on N-rGO was prepared via a simple hydrothermal and self-assembly process. For optimization of Pr content, three (0.1, 0.5, and 0.8) different doping ratios were investigated. A lithium-ion battery assembled with NiPr0.5 FeP/N-rGO electrode achieved an outstanding specific capacity of 1.61 Ah g-1 at 0.2 A g-1 after 100 cycles with 99.3 % Coulombic efficiencies. A prolonged cycling stability of 1.02 Ah g-1 was maintained even after 1000 cycles at 0.5 A g-1 . In addition, a full cell battery with NiPr0.5 FeP/N-rGO∥LCO (Lithium cobalt oxide) delivered a promising cycling performance of 0.52 Ah g-1 after 200 cycles at 0.15 A g-1 . Subsequently, the NiPr0.5 FeP/N-rGO electrode in a direct borohydride fuel cell showed the highest peak power density of 93.70 mW cm-2 at 60 °C. Therefore, this work can be extended to develop advanced electrode for next-generation energy storage and conversion systems.

Lattice strain controlled Ni@NiCu efficient anode catalysts for direct borohydride fuel cells

We successfully fabricated a novel tensile lattice strained Ni@NiCu catalyst with a popcorn-like morphology, which is composed of a crystalline Ni core and a NiCu alloy shell. It exhibits outstanding catalytic activity, selectivity, and stability towards borohydride electrooxidation. Moreover, a direct borohydride fuel cell (DBFC) with a Ni@NiCu anode can deliver a power density of 433 mW cm-2 and an open circuit voltage of 1.94 V, much better than the performances of DBFCs employing other anode catalysts reported in the literature. This could be attributed to the fact that the tensile lattice strain generated by the introduction of Cu leads to a rise in the d-band center of the Ni metal and promotes the final B-H decoupling, which is the rate-determining step in the borohydride oxidation reaction, thus improving remarkably the catalytic performances of Ni@NiCu.

Succulent-plant-like Ni-Co alloy efficient catalysts for direct borohydride fuel cells

A Ni-Co alloy catalyst with a unique succulent-plant-like morphology is prepared by a simple electrodeposition method, while the effects of deposition conditions on its performance are also investigated systematically. The research results show that the Ni_0.889-Co_0.111 catalyst exhibits excellent activity, selectivity, and stability to the borohydride oxidation reaction. Moreover, when Ni_0.889-Co_0.111 is assembled as the anode catalyst, the direct borohydride fuel cell delivers a peak power density of 490 mW cm^-2 and an open-circuit voltage of 1.87 V at 343 K and can run stably for dozens of hours. The significant improvement in Ni-Co catalyst performance can be attributed to its unique succulent-plant-like morphology and the introduction of an appropriate amount of Co.