Ultrathin Ultralow-Platinum Catalyst Coated Membrane for Proton Exchange Membrane Fuel Cells.

Catalyst coated membrane (CCM) is the core component of proton exchange membrane fuel cells and is routinely fabricated by spraying Pt/C slurries onto membrane, resulting in low activity and thick catalyst layer (CL, 5-10 µm) with an unaffordable Pt loading of 0.2-0.4 mg cm-2 and a large mass transfer resistance at cathode. Highly active ultrathin ultralow-Pt CL (UUCL) is urgently required, but remains rare. Herein, wet-chemical direct growth of UUCLs on both sides of membrane to achieve integrated ultrathin ultralow-Pt catalyst coated membranes (UUCCMs) with a cathodic CL thickness of 79.7 ± 15.0 nm and a Pt loading of 20.2 ± 1.6 µg cm-2 is reported. The key to this unique fabrication is the release of proton from membrane to regioselectively initiate the growth of interconnected Pd nanoneedle clusters array on membrane, followed by high-density deposition of Pt nanoparticles on Pd (Pt/Pd UUCLs). The single cell of UUCCMs exhibits the highest mass peak power density of 59.9 W mgPt,Cathode -1 in the literature. The exceptional activity originates from high electrochemically active surface area, remarkable oxygen reduction reaction activity closely correlated with strain, and electronic effect at Pt/Pd interface, as well as improved mass transfer and optimal water management.

Ultrafine IrRu Nanoparticles toward Efficient Oxygen Evolution Reaction in Acidic Media.

Proton exchange membrane water electrolyzers (PEMWEs) are capable of mass-producing green hydrogen with renewable and wave-trough electricity, but confront the challenge of the lack of advanced electrocatalysts to accelerate sluggish oxygen evolution reaction (OER). Herein, we report the synthesis of ultrafine IrRu alloy nanoparticles (1.6 ± 0.3 nm) by coprecipitation of IrCl3, RuCl3, and HCOONa in water to allow Ir3+ and Ru3+ to be well dispersed and enclosed in the matrix of crystalline HCOONa, followed by heat treatment of HCOONa to reduce Ir3+ and Ru3+. Remarkably, the overpotential of IrRu toward acidic OER at 10 mA cm-2 is merely 230 and 194 mV at 51 and 204 µgIrRu cm-2, respectively. The high electrochemically active surface area (ECSA) of 577.1 m2 g-1 and high specific activity (SA) of 22.7 µA cm-2 at 1.45 V vs RHE would contribute to the exceptional OER activity. In addition, the electron transfer from Ir to Ru in IrRu should significantly boost the OER activity according to X-ray photoelectron spectroscopy (XPS). IrRu also shows an excellent stability during 10 h of a chronopotentiometry (CP) test at 10 mA cm-2. Eventually, the high OER activity of IrRu was verified in a PEMWE.