Coaxial Nanowire Electrodes Enable Exceptional Fuel Cell Durability.

Polymer-electrolyte-membrane fuel cells (PEMFCs) hold great promise for applications in clean energy conversion, but cost and durability continue to limit commercialization. This work presents a new class of catalyst/electrode architecture that does not rely on Pt particles or carbon supports, eliminating the primary degradation mechanisms in conventional electrodes, and thereby enabling transformative durability improvements. The coaxial nanowire electrode (CANE) architecture consists of an array of vertically aligned nanowires, each comprising an ionomer core encapsulated by a nanoscale Pt film. This unique design eliminates the triple-phase boundary and replaces it with two double-phase boundaries, increasing Pt utilization. It also eliminates the need for carbon support and ionomer binder, enabling improved durability and faster mass transport. Fuel cell membrane electrode assemblies based on CANEs demonstrate extraordinary durability in accelerated stress tests (ASTs), with only 2% and 5% loss in performance after 5000 support AST cycles and 30000 catalysts AST cycles, respectively. The high power density and extremely high durability provided by CANEs can enable a paradigm shift from random electrodes based on unstable platinum nanoparticles dispersed on carbon to ordered electrodes based on durable Pt nanofilms, facilitating rapid deployment of fuel cells in transportation and other clean energy applications.

Carbon nanotube encapsulated metal selenide nanostructures for efficient electrocatalytic oxygen evolution reaction.

Nickel selenide nanowires were grown inside carbon nanotubes through in situ encapsulation via one-step chemical vapor deposition. These NiSe2@CNT nanohybrids showed excellent electrocatalytic activity for water splitting with a low overpotential of 260 mV at 10 mA cm-2, high current density, and extended stability owing to the synergistic effect between NiSe2 and CNTs.

Textured NiSe2 Film: Bifunctional Electrocatalyst for Full Water Splitting at Remarkably Low Overpotential with High Energy Efficiency.

Herein we have shown that electrodeposited NiSe2 can be used as a bifunctional electrocatalyst under alkaline conditions to split water at very low potential by catalyzing both oxygen evolution and hydrogen evolution reactions at anode and cathode, respectively, achieving a very high electrolysis energy efficiency exceeding 80% at considerably high current densities (100 mA cm-2). The OER catalytic activity as well as electrolysis energy efficiency surpasses any previously reported OER electrocatalyst in alkaline medium and energy efficiency of an electrolyzer using state-of-the-art Pt and RuO2 as the HER and OER catalyst, respectively. Through detailed electrochemical and structural characterization, we have shown that the enhanced catalytic activity is attributed to directional growth of the electrodeposited film that exposes a Ni-rich lattice plane as the terminating plane, as well as increased covalency of the selenide lattice which decreases the Ni(II) to Ni(III) oxidation potential. Thereby, the high efficiency along with extended stability makes NiSe2 as the most efficient water electrolyzer known to-date.

Cobalt Selenide Nanostructures: An Efficient Bifunctional Catalyst with High Current Density at Low Coverage.

Electrodeposited Co7Se8 nanostructures exhibiting flake-like morphology show bifunctional catalytic activity for oxygen evolution and hydrogen evolution reaction (OER and HER, respectively) in alkaline medium with long-term durability (>12 h) and high Faradaic efficiency (99.62%). In addition to low Tafel slope (32.6 mV per decade), the Co7Se8 OER electrocatalyst also exhibited very low overpotential to achieve 10 mA cm(-2) (0.26 V) which is lower than other transition metal chalcogenide based OER electrocatalysts reported in the literature and significantly lower than the state-of-the-art precious metal oxides. A low Tafel slope (59.1 mV per decade) was also obtained for the HER catalytic activity in alkaline electrolyte. The OER catalytic activity could be further improved by creating arrays of 3-dimensional rod-like and tubular structures of Co7Se8 through confined electrodeposition on lithographically patterned nanoelectrodes. Such arrays of patterned nanostructures produced exceptionally high mass activity and gravimetric current density (∼68 000 A g(-1)) compared to the planar thin films (∼220 A g(-1)). Such high mass activity of the catalysts underlines reduction in usage of the active material without compromising efficiency and their practical applicability. The catalyst layer could be electrodeposited on different substrates, and an effect of the substrate surface on the catalytic activity was also investigated. The Co7Se8 bifunctional catalyst enabled water electrolysis in alkaline solution at a cell voltage of 1.6 V. The electrodeposition works with exceptional reproducibility on any conducting substrate and shows unprecedented catalytic performance especially with the patterned growth of catalyst rods and tubes.