Endowing transition-metal oxide electrocatalysts with high water oxidation activity is greatly desired for production of clean and sustainable chemical fuels. Here, we present an atomically thin cobalt oxyhydroxide (γ-CoOOH) nanosheet as an efficient electrocatalyst for water oxidation. The 1.4 nm thick γ-CoOOH nanosheet electrocatalyst can effectively oxidize water with extraordinarily large mass activities of 66.6 A g(-1), 20 times higher than that of γ-CoOOH bulk and 2.4 times higher than that of the benchmarking IrO2 electrocatalyst. Experimental characterizations and first-principles calculations provide solid evidence to the half-metallic nature of the as-prepared nanosheets with local structure distortion of the surface CoO(6-x) octahedron. This greatly enhances the electrophilicity of H2O and facilitates the interfacial electron transfer between Co ions and adsorbed -OOH species to form O2, resulting in the high electrocatalytic activity of layered CoOOH for water oxidation.

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Abstract-Massive MIMO is a promising technology in future wireless communication networks. However, it raises a lot of implementation challenges, for example, the huge pilot symbols and feedback overhead, requirement of real-time global CSI, large number of RF chains needed and high computational complexity. We consider a two-tier precoding strategy for multi-cell massive MIMO interference networks, with an outer precoder for inter-cell/inter-cluster interference cancellation, and an inner precoder for intra-cell multiplexing. In particular, to combat with the computational complexity issue for the outer precoding, we propose a low complexity online iterative algorithm to track the outer precoder under time-varying channels. We follow an optimization technique and formulate the problem on the Grassmann manifold. We develop a low complexity iterative algorithm, which converges to the global optimal solution under static channels. In time-varying channels, we propose a compensation technique to offset the variation of the time-varying optimal solution. We show with our theoretical result that, under some mild conditions, perfect tracking of the target outer precoder using the proposed algorithm is possible. Numerical results demonstrate that the two-tier precoding with the proposed iterative compensation algorithm can achieve a good performance with a significant complexity reduction compared with the conventional two-tier precoding techniques in the literature.

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The deficiency of robust and practical methods for 18F-radiofluorination is a bottleneck for positron emission tomography (PET) tracer development. Here, we report the first transition-metal-assisted 18F-deoxyfluorination of phenols. The transformation benefits from readily available phenols as starting materials, tolerance of moisture and ambient atmosphere, large substrate scope, and translatability to generate doses appropriate for PET imaging.

Endowing transition‐metal oxide electrocatalysts with high water oxidation activity is greatly desired for production of clean and sustainable chemical fuels. Here, we present an atomically thin cobalt oxyhydroxide (γ‐CoOOH) nanosheet as an efficient electrocatalyst for water oxidation. The 1.4 nm thick γ‐CoOOH nanosheet electrocatalyst can effectively oxidize water with extraordinarily large mass activities of 66.6 A g−1, 20 times higher than that of γ‐CoOOH bulk and 2.4 times higher than that of the benchmarking IrO2 electrocatalyst. Experimental characterizations and first‐principles calculations provide solid evidence to the half‐metallic nature of the as‐prepared nanosheets with local structure distortion of the surface CoO6−x octahedron. This greatly enhances the electrophilicity of H2O and facilitates the interfacial electron transfer between Co ions and adsorbed ‐OOH species to form O2, resulting in the high electrocatalytic activity of layered CoOOH for water oxidation.