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Carbon-supported nanocomposites are attracting particular attention as high-performance, low-cost electrocatalysts for electrochemical water splitting. These are mostly prepared by pyrolysis and hydrothermal procedures that are time-consuming (from hours to days) and typically difficult to produce a nonequilibrium phase. Herein, for the first time ever, we exploit magnetic induction heating-quenching for ultrafast production of carbon-FeNi spinel oxide nanocomposites (within seconds), which exhibit an unprecedentedly high performance towards oxygen evolution reaction (OER), with an ultralow overpotential of only +260 mV to reach the high current density of 100 mA cm-2. Experimental and theoretical studies show that the rapid heating and quenching process (ca. 103 K s-1) impedes the Ni and Fe phase segregation and produces a Cl-rich surface, both contributing to the remarkable catalytic activity. Results from this study highlight the unique advantage of ultrafast heating/quenching in the structural engineering of functional nanocomposites to achieve high electrocatalytic performance towards important electrochemical reactions.

Sustainable fuel production from CO2 through electrocatalytic reduction is promising but challenging due to high overpotential and poor product selectivity. Herein, we computed the reaction free energies of electrocatalytic CO2...

chalcogenides, [5,6] halides, [7,8] and some complicated salts (e.g., Chevreul's salt), [9] which have found diverse applications, such as catalysis, [10,11] sensing, [12,13] energy conversion, [14,15] and optics. [16] Amongst these, cuprous oxide (CuOH) has long been attracting extensive interest. [17,18] Back in the early 1900s, Miller and Gillett observed that when a NaCl solution was electrolyzed with copper working electrodes at low temperatures (below 60 °C), yellow CuOH precipitates were produced. [19,20] Subsequently, several studies were conducted to investigate the characteristic structure and properties of CuOH synthesized via various methods. [21][22][23] Nevertheless, in these early studies, CuOH was mostly in the bulk solid form and structurally metastable, where the yellowish precipitates would rapidly change the color appearance to dark red, signifying the formation of Cu 2 O, upon exposure to the ambient or thermal treatment due to the lack of proper protection from oxidation and/or dehydration. Such structural instability makes it difficult to study the properties and applications of the obtained CuOH. In 2012, Korzhavyi et al. [24] carried out theoretical studies and demonstrated that CuOH could exist in a solid form; yet the metastability led to the formation of a random mixture of various configurations in the crystal structure, such as Cu 2 O and ice VII H 2 O. SorokaCopper compounds have been extensively investigated for diverse applications. However, studies of cuprous hydroxide (CuOH) have been scarce due to structural metastability. Herein, a facile, wet-chemistry procedure is reported for the preparation of stable CuOH nanostructures via deliberate functionalization with select organic ligands, such as acetylene and mercapto derivatives. The resulting nanostructures are found to exhibit a nanoribbon morphology consisting of small nanocrystals embedded within a largely amorphous nanosheet-like scaffold. The acetylene derivatives are found to anchor onto the CuOH forming CuC linkages, whereas CuS interfacial bonds are formed with the mercapto ligands. Effective electronic coupling occurs at the ligand-core interface in the former, in contrast to mostly nonconjugated interfacial bonds in the latter, as manifested in spectroscopic measurements and confirmed in theoretical studies based on first principles calculations. Notably, the acetylene-capped CuOH nanostructures exhibit markedly enhanced photodynamic activity in the inhibition of bacteria growth, as compared to the mercapto-capped counterparts due to a reduced material bandgap and effective photocatalytic generation of reactive oxygen species. Results from this study demonstrate that deliberate structural engineering with select organic ligands is an effective strategy in the stabilization and functionalization of CuOH nanostructures, a critical first step in exploring their diverse applications.