The broad employment of water electrolysis for hydrogen (H₂) production is restricted by its large voltage requirement and low energy conversion efficiency because of the sluggish oxygen evolution reaction (OER). Herein, we report a strategy to replace OER with a thermodynamically more favorable reaction, the partial oxidation of formaldehyde to formate under alkaline conditions, using a Cu₃Ag₇electrocatalyst. Such a strategy not only produces more valuable anodic product than O₂but also releases H₂at the anode with a small voltage input. Density functional theory studies indicate the H₂C(OH)O intermediate from formaldehyde hydration can be better stabilized on Cu₃Ag₇than on Cu or Ag, leading to a lower C-H cleavage barrier. A two-electrode electrolyzer employing an electrocatalyst of Cu₃Ag₇(+)||Ni₃N/Ni(–) can produce H₂at both anode and cathode simultaneously with an apparent 200% Faradaic efficiency, reaching a current density of 500 mA/cm²with a cell voltage of only 0.60 V.

We report on the integration of atomically thin 2D insulating hexagonal boron nitride (h-BN) tunnel barriers into Co/h-BN/Fe magnetic tunnel junctions (MTJs). The h-BN monolayer is directly grown by chemical vapor deposition on Fe. The Conductive Tip Atomic Force Microscopy (CT-AFM) measurements reveal the homogeneity of the tunnel behavior of our h-BN layers. As expected for tunneling, the resistance depends exponentially on the number of h-BN layers. The h-BN monolayer properties are also characterized through integration into complete MTJ devices. A Tunnel Magnetoresistance of up to 6% is observed for a MTJ based on a single atomically thin h-BN layer.

Selective subatomic separations: Membranes are thin materials used to selectively separate gases or liquids and are used on a range of scales from benchtop experiments to industrial processes. Challenges arise in separating materials with very similar sizes or chemical properties, particularly at the smallest scales. Kidambi et al . review advances in using atomically thin two-dimensional materials such as graphene or hexagonal boron nitride for the separation of subatomic species, including electrons, hydrogen isotopes, and gases. The authors explore the scope to scale up the sizes of these membranes and their potential use in applications relating to energy, microscopy, and electronics. —MSL

We report on the integration of atomically thin 2D insulating hexagonal boron nitride (h-BN) tunnel barriers into magnetic tunnel junctions (2D-MTJs) by fabricating two illustrative systems (Co/h-BN/Co and Co/h-BN/Fe) and by discussing h-BN potential for metallic spin filtering. The h-BN is directly grown by chemical vapor deposition on prepatterned Co and Fe stripes. Spin-transport measurements reveal tunnel magneto-resistances in these h-BN-based MTJs as high as 12% for Co/h-BN/h-BN/Co and 50% for Co/h-BN/Fe. We analyze the spin polarizations of h-BN/Co and h-BN/Fe interfaces extracted from experimental spin signals in light of spin filtering at hybrid chemisorbed/physisorbed h-BN, with support of ab initio calculations. These experiments illustrate the strong potential of h-BN for MTJs and are expected to ignite further investigations of 2D materials for large signal spin devices.