Iridium (Ir) nanostructures with well-defined shapes, and particularly, highly active surface, are attractive for the application of electrocatalytic oxygen evolution reaction (OER), yet they have had very limited success to date because of challenges in their synthesis. Here, we report the synthesis of Ir nanocrystals, in the form of Pd@Ir core–shell structures and with well-defined high-index {331} facets, by a robust seed-mediated process. The success relies on the precise control over the deposition of ultrathin Ir layer on Pd trioctahedral nanocrystals. The Pd@Ir nanocatalyst with such unique high-index facets delivers substantially promoted OER activity and durability compared with those with low-index facets (i.e., {100} and {111} facets), with an overpotential as low as 300 mV, boosted mass activities up to 1.01 A mgIr –1 at 1.53 V, and a minimal Tafel slope of 84.9 mV dec–1. Density functional theory (DFT) calculations suggest that the superior OER performance originates from the easier hydroxylation of *O to *OOH over high-index facets, along with the appropriate value of ΔG O-ΔG OH and satisfactory adsorption/desorption property. Moreover, the high-index facets are apt to be electrochemically oxidized into stable IrO x species, leading to an improved durability. Both theoretical and experimental studies demonstrate the fascinating property of a high-index Ir shell in facilitating OER activity and durability.

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Solar CO2 reduction via photocatalysis enables sustainable carbon-cycle utilization, yet a challenge to date because of the relatively low conversion efficiency. Herein, we demonstrate that this photocatalytic process could be significantly improved by coupling an alternating magnetic field (AMF). Using NiO/TiO2 as a model photocatalyst, CO2 could be converted into CH4 in the presence of H2O vapor. Integrating with AMF, the conversion of CO2 to CH4 increased by 213%. The enhanced photocatalysis process by AMF coupling can not only increase the carrier density by inhibiting the combination of photogenerated electron-hole pairs, but also improve the oxidation ability of the catalyst under simulated sunlight, and promote the conversion of H2O to O2. Our investigation also elucidates that the Ni species act as the adsorption/activation sites of CO2 to promote the reduction of CO2 to CH4. This work opens a new research door in solar CO2 reduction by integrating AMF into photocatalysis.