Interface-Engineered NiFe/Ni-S Nanoparticles for Reliable Alkaline Oxygen Production at Industrial Current: A Sulfur Source Confinement Strategy.

Using powder-based ink appears to be the most suitable candidate for commercializing the membrane electrode assembly (MEA), while research on the powder-based NPM catalyst for anion exchange membrane water electrolyzer (AEMWE) is currently insufficient, especially at high current density. Herein, a sulfur source (NiFe Layered double hydroxide adsorbed SO 4 2 - ${\mathrm{SO}}_4^{2 - }$ ) confinement strategy is developed to integrate Ni3S2 onto the surface of amorphous/crystalline NiFe alloy nanoparticles (denoted NiFe/Ni-S), achieving advanced control over the sulfidation process for the formation of metal sulfides. The constructed interface under the sulfur source confinement strategy generates abundant active sites that increase electron transport at the electrode-electrolyte interface and improve ability over an extended period at a high current density. Consequently, the constructed NiFe/Ni-S delivers an ultra-low overpotential of 239 mV at 10 mA cm-2 and 0.66 mA cm ECSA - 2 ${\mathrm{cm}}_{{\mathrm{ECSA}}}^{ - 2}$ under an overpotential of 300 mV. The AEMWE with NiFe/Ni-S anode exhibits a cell voltage of 1.664 V @ 0.5 A cm-2 and a 400 h stability at 1.0 A cm-2.

Fast Current-Driven Synthesis of ZIF-Derived Catalyst Layers for High-Performance Zn-Air Battery.

As a core component, the catalyst layer (CL) is widely used in fuel cell, metal-air battery, and other energy conversion devices. Herein, a highly efficient method for CL preparation via fast current-driven synthesis followed by pyrolysis is proposed. Compared with previously reported fabrication procedures of zeolite imidazolate frameworks (ZIF)-based CLs, this method directly deposits the ZIF precursor onto the conductive substrate in a very short time (≤15 min). The self-supporting CL, converted from ZIF membrane by simple single-step pyrolysis, is assembled with the gas diffusion layer to obtain cathode. Electrochemical tests exhibit a small potential gap (0.83 V) between the oxygen reduction and evolution reactions, as well as high performance and excellent stability for Zn-air battery (241 mW cm-2 at 390 mA cm-2 ), due to the unique design of a bi-continuous framework (interconnected pores and long carbon nanotubes) and Co-based active sites. This work may provide new directions for the fast fabrication of non-platinum group metal CLs for metal-air batteries or fuel cell applications.

Space Confinement to Regulate Ultrafine CoPt Nanoalloy for Reliable Oxygen Reduction Reaction Catalyst in PEMFC.

A Co-based zeolitic imidazolate framework (ZIF-67) derived catalyst with ultrafine CoPt nanoalloy particles is designed via a two-step space confinement method, to achieve a robust oxygen reduction reaction (ORR) performance for proton exchange membrane fuel cell (PEMFC). The core-shell structure of ZIF-67 (core) and SiO2 (shell) is carefully adjusted to inhibit the agglomeration of Co nanoparticles. In the subsequent adsorption-annealing process, the in situ formed graphene shell on the surface of Co nanoparticles further protects metal particles from coalescence, leading to the ultrafine CoPt nanoalloy (average diameter is 2.61 nm). Benefitting from the high utilization of Pt metal, the mass activity of CoPt nanoalloy catalyst reaches 681.8 mA mgPt -1 at 0.9 V versus RHE according to the rotating disk electrode test in 0.1 m HClO4 solution. The CoPt nanoalloy-based PEMFC provides a high maximum power density of 2.22 W cm-2 (H2 /O2 ) and 0.923 W cm-2 (H2 /air). Simultaneously, it shows good stability in the long-time dynamic test at low humidity, due to the robust CoPt@graphene core-shell nanostructure. This work provides a viable strategy for designing Pt-based nanoalloy catalysts with ultrafine metal particles and high stability.