We generate terahertz (THz) transients by illuminating a few-nanometer-thick Ta/NiFe/Pt nanolayers with a train of linearly polarized 100fs-wide laser pulses. The transients are $1-ps-wide free-space propagating bursts of electromagnetic radiations with amplitudes that are magnetically and optically tunable. Their spectral frequency content extends up to 5 THz, and the 3-dB cutoff is at 0.85 THz. The observed transient electromagnetic signals originate from the NiFe/Pt bilayer, and their amplitude dependence on the external magnetic field, applied in the sample plane, very closely follows the static magnetization versus magnetic field dependence of the NiFe film. For the same laser power, excitation with highly energetic, blue light generates THz transients with amplitudes approximately three times larger than the ones resulting from excitation by infrared light. In both cases, the transients exhibit the same spectral characteristics and are linearly polarized in the perpendicular direction to the sample magnetization. The polarization direction can be tuned by rotation of the magnetic field around the laser light propagation axis. The characteristics of our THz spintronic emitter signals confirm that THz transient generation is due to the inverse spin Hall effect in the Pt layer and demonstrate that ferromagnet/metal nanolayers excited by femtosecond laser pulses can serve as efficient sources of magnetically and optically tunable, polarized transient THz radiation.

While copper-based electrocatalysts are strong contenders for the electrochemical reduction of CO2 (ERCO2) to C1 products (CO and formic acid) as feedstock for the energy and industry, their selectivity is a tricky issue. Herein, we propose a strategy to modulate the selectivity by equipped with various functional groups (N–, G–, −COOH, −NH2, and −OH) to affect the adsorption of key intermediates on the surface of Cu-based electrocatalysts. Among these as-prepared catalysts, the catalysts equipped with N– and −OH functional groups show excellent catalytic performance for ERCO2 with nearly 90% selectivities for C1 products. Moreover, the N– functional group has favorable formate selectivity when compared with the pristine Cu-based electrocatalyst. By investigating the catalysts’ electrochemical performance, it is demonstrated that the interactions between functional groups and catalytic active sites are critical in regulating the catalytic selectivity of electrocatalysts. According to economic feasibility analysis, it is further proven that this design principle can be applied on a larger scale.

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