Hydrogen produced with no greenhouse gas emissions is termed "green hydrogen" and will be essential to reaching decarbonization targets set forth by nearly every country as per the Paris Agreement. Proton exchange membrane water electrolyzers (PEMWEs) are expected to contribute substantially to the green hydrogen market. However, PEMWE market penetration is insignificant, accounting for less than a gigawatt of global capacity. Achieving substantive decarbonization via green hydrogen will require PEMWEs to reach capacities of hundreds of gigawatts by 2030. This paper serves as an overarching roadmap for cell-level improvements necessary for gigawatt-scale PEMWE deployment, with insights from three well-established hydrogen technology companies included. Analyses will be presented for economies of scale, renewable energy prices, government policies, accelerated stress tests, and component-specific improvements.

Our results validate the use of independent DFT predicted BE shifts for defect identification and constraining ambient pressure XPS observations for Me–N_x moieties in pyrolyzed carbon based ORR electrocatalysts. This supports the understanding of such catalysts as vacancy-and-substitution defects in a graphene-like matrix.

Electrocatalytic reduction of waste nitrates (NO₃⁻) enables the synthesis of ammonia (NH₃) in a carbon neutral and decentralized manner. Atomically dispersed metal-nitrogen-carbon (M-N-C) catalysts demonstrate a high catalytic activity and uniquely favor mono-nitrogen products. However, the reaction fundamentals remain largely underexplored. Herein, we report a set of 14; 3d-, 4d-, 5d- and f-block M-N-C catalysts. The selectivity and activity of NO₃⁻ reduction to NH₃ in neutral media, with a specific focus on deciphering the role of the NO₂⁻ intermediate in the reaction cascade, reveals strong correlations (R=0.9) between the NO₂⁻ reduction activity and NO₃⁻ reduction selectivity for NH₃. Moreover, theoretical computations reveal the associative/dissociative adsorption pathways for NO₂⁻ evolution, over the normal M-N₄ sites and their oxo-form (O-M-N₄) for oxyphilic metals. This work provides a platform for designing multi-element NO₃RR cascades with single-atom sites or their hybridization with extended catalytic surfaces.