Shengwen Li

Self‐assembling molecules (SAM) have been widely used in inverted perovskite solar cells (PSC) as a hole transfer layer due to nearly lossless charge transfer giving excellent device performance. However, the energy level alignment between SAM‐ and PSC‐related interfaces has not been systematically studied. Herein, the 2PACz, a typical SAM with the largest dipole moment, is chosen as the model system and is studied by vacuum deposition. It is found that the energy level alignment is determined by the orientation of 2PACz molecules on a different substrate. The molecules are lying down on highly oriented pyrolytic graphite and giving nearly zero interface dipole. On solvent‐cleaned and plasma‐treated indium tin oxide (ITO) substrates, the SAM is vertically assembled with 0.22 and 0.13 eV work function increases, respectively. However, on sputtered ITO, SAM is assembled with upside down orientation, with 0.51 eV work function decrease. The change of orientation is due to strong interaction between oxygen vacancies in ITO substrate and carbazole head group of 2PACz. On perovskite film, SAM also shows a slightly upward orientation with additional passivation of free MA⁺ ions. Herein, it is confirmed that the energy level alignment of SAM plays an important role in hole extraction.

High-efficiency non-precious electrocatalysts are urgently demanded in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Transition metal oxide catalysts have shown high activity for the OER in alkaline medium, however, they are generally inactive for the HER. Here, we report an aliovalent fluorine anion substitution and anodization-induced amorphization strategy to enhance the HER activity of CoO and concomitantly obtain the optimal OER performance. Aliovalent fluorine anions at O²⁻ sites significantly induce the charge redistribution of neighboring Co sites, facilitate water dissociation and weaken hydrogen adsorption, enabling the optimal states for the HER. More importantly, the anodization causes F-leaching-assisted amorphization, which leads to the formation of a highly catalytic shell for the OER. When using F-CoO as the bifunctional catalyst, a low cell voltage of 1.53 V is observed to drive a current density of 10 mA cm⁻², which is superior to that of noble-metal-based Pt/C–IrO₂. This work provides a novel strategy of aliovalent fluorine anion substitution to dramatically activate transition metal oxides for overall water splitting.

Aiming at the poor dynamic performance of DC solid transformer with dual-loop control, a three-loop control method is proposed for the DC transformer to improve the system dynamic performance. The proposed control method is implemented by introducing an output current loop to the traditional dual-loop control system. Simulation results show the effective of the proposed method.

Electrolysis of water needs high-efficiency catalysts to accelerate the kinetics of the hydrogen evolution reaction (HER). A single catalyst is usually unable to simultaneously and effectively enhance all elementary steps of the HER. In this study, we demonstrate a novel triple-phase interface design that includes NiO and Ru nanoparticles on a porous nickel scaffold (PNS) to promote the Volmer and Heyrovsky steps, respectively. An in situ electro-oxidation route is developed to enable two catalysts along the interfaces to be directly wired with the metallic PNS. Because the hydrogen intermediates and electrons can be easily transported through the triple-phase interfaces, such a triple-phase interface structure exhibits highly efficient synergistic catalysis that is not observed in a conventional combination of two catalysts. The resultant electrocatalyst shows an overpotential of 39 mV at −10 mA cm⁻² and a low Tafel slope of 75 mV dec⁻¹ in 1 M KOH electrolyte, which are comparable to Pt/C and superior to other non-Pt electrocatalysts. Our studies demonstrated that interface construction of bifunctional catalysts can serve as an effective approach to promote the activities of non-Pt catalysts.