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ABSTRACT In this paper, the iCGF−1 mode is proposed to compensate the amplitude‐to‐amplitude modulation (AM/AM) distortion of the traditional continuous class F−1 mode while maintaining the high efficiency. The AM/AM profile of the iCGF−1 mode is mathematically expressed simultaneously as a function of the input nonlinearity parameter γ$$ \gamma $$ and conduction angle α$$ \alpha $$, which makes the iCGF−1 mode more flexible in controlling the AM/AM profile. The first inflection point of the AM/AM profile can be moved to a higher output power level through theoretical deduction by adjusting the second harmonic source impedance Z2S$$ {Z}_{2S} $$ and gate bias voltage to increase the values of γ$$ \gamma $$ and α$$ \alpha $$. This flattens the AM/AM profile while the efficiency profile remains almost the same as that of the traditional continuous class F−1 mode. The performance of the iCGF−1 mode is verified through simulation and experimental measurements. The iCGF−1 PA is fabricated with CGH40010F and has a frequency range of 2–2.6 GHz. The drain efficiency is 70.1%–77.9%, and the output power is 41.1–41.7 dBm. The linearity is tested with a 100 MHz 5G NR signal (the peak average power ratio (PAPR) is 8.5 dB) at 2.3 GHz. The worst adjacent channel power ratio (ACPR) is −32.3 dBc without digital predistortion (DPD) and −52.1 dBc with DPD. The results show that the iCGF−1 mode has successfully compensated the AM/AM distortion of the traditional continuous class F−1$$ {}^{-1} $$ mode and maintaining high efficiency. [ABSTRACT FROM AUTHOR]

Two-dimensional silicon (Si) nanosheets are becoming increasingly exciting for photocatalytic applications. Their unique morphology and physiochemical properties make it attractive in heterojunction engineering. In this work, we report the construction of 2D H–Si/g-C3N4 hybrid as a heterojunction photocatalyst for solar photocatalytic hydrogen evolution. The exfoliated silicon nanosheets etched by hydrofluoric acid exhibit a hydrogen-terminated surface with an inverse charging state, which can thus be easily anchored onto g-C3N4 nanosheets by self-assembly. The optimized H–Si/g-C3N4 heterojunction photocatalyst with Pt as the cocatalyst achieved an improved photocatalytic hydrogen production rate which is about 2 times that of g-C3N4 nanosheets under simulated sunlight irradiation using methanol as the sacrificial agent. Density functional theory calculations revealed that the built-in electric field (BIEF) at the H–Si/g-C3N4 interface contributes to the spatial charge separation of the heterojunction. The BIEF leads to an S-scheme carrier transfer mechanism at the H–Si/g-C3N4 interface that benefits the carrier separation on g-C3N4 nanosheets, resulting in uniform deposition of the Pt cocatalyst at the heterojunction interface and improved photocatalytic performance. This work not only expands the application of silicon nanosheets by supporting the potential of 2D H–Si/g-C3N4 heterojunction in photocatalytic reactions but also provides valuable insights to the interface behavior of the H–Si/g-C3N4 heterostructure. [ABSTRACT FROM AUTHOR]

Abstract:Catalyst surface dynamics drive the generation of active species for electrocatalytic reactions. Yet, the understanding of dominant site formation and reaction mechanisms is limited. In this study, we thoroughly investigate the dynamic reconstruction of two‐dimensional defective Bi nanosheets from exfoliated Bi2Se3 nanosheets under electrochemical CO2 and nitrate (NO3−) reduction conditions. The ultrathin Bi2Se3 nanosheets obtained by NaBH4‐assisted cryo‐mediated liquid‐phase exfoliation are more easily reduced and reconstructed to Bi nanosheets with high‐density grain boundaries (GBs; GB‐rich Bi). The reconstructed GB‐rich Bi catalyst affords a remarkable yield rate of 4.6 mmol h−1 mgcat.−1 and Faradaic efficiency of 32 % for urea production at −0.40 V vs. RHE. Notably, this yield rate is 2 and 8.2 times higher than those of the low‐GB Bi and bulk Bi catalysts, respectively. Theoretical analysis demonstrates that the GB sites significantly reduce the *CO and *NH2 intermediate formation energy and C−N coupling energy barrier, enabling selective urea electrosynthesis on the GB‐rich Bi catalyst. This work will trigger further research into the structure‐activity interplay in dynamic processes using in situ techniques. [ABSTRACT FROM AUTHOR]