Cost-effective electrocatalysts for the oxygen evolution reaction (OER) are critical to energy conversion and storage processes. A novel strategy is used to synthesize a non-noble-metal-based electrocatalyst of the OER by finely combining layered FeNi double hydroxide that is catalytically active and electric conducting graphene sheets, taking advantage of the electrostatic attraction between the two positively charged nanosheets. The synergy between the catalytic activity of the double hydroxide and the enhanced electron transport arising from the graphene resulted in superior electrocatalytic properties of the FeNi-GO hybrids for the OER with overpotentials as low as 0.21 V, which was further reduced to 0.195 V after the reduction treatment. Moreover, the turnover frequency at the overpotential of 0.3 V has reached 1 s(-1), which is much higher than those previously reported for non-noble-metal-based electrocatalysts.

We report on the synthesis of iron-nickel sulfide (INS) ultrathin nanosheets by topotactic conversion from a hydroxide precursor. The INS nanosheets exhibit excellent activity and stability in strong acidic solutions as a hydrogen evolution reaction (HER) catalyst, lending an attractive alternative to the Pt catalyst. The metallic α-INS nanosheets show an even lower overpotential of 105 mV at 10 mA/cm2 and a smaller Tafel slope of 40 mV/dec. With the help of DFT calculations, the high specific surface area, facile ion transport and charge transfer, abundant electrochemical active sites, suitable H+ adsorption, and H2 formation kinetics and energetics are proposed to contribute to the high activity of the INS ultrathin nanosheets toward HER.

enhanced device performance. [3b] Besides, 2D perovskite also has been deposited by cation exchange or spin-casting onto CH 3 NH 3 PbI 3 crystalline films as a capping layer to improve device stability. [4] To our knowledge, however, such as capping layer has always imposed a significant barrier to charge transfer due to the quantum-confined energy level structure of 2D perovskite. [3a,b] Herein, we developed a solution process based in situ growth route, which allowed us to form a 2D capping layer together with 3D perovskite, essentially a 3D-2D graded interface. Remarkably, the 3D-2D graded perovskite layer was made atomically sharp at the near surface by using such a simple in situ growth process. More importantly, that dimensionally graded layer advantageously modified the interface energy level, consequently reduced the charge recombination at a perovskite/phenyl-C 61 -butyric acid methyl ester (PCBM) interface, and at the same time facilitated the interfacial charge transfer. This innovation has led to a pronounced promotion of the performance of NiO based p-i-n solar cells, with V oc reaching up to 1.17 V, which is among the highest for triiodide perovskite on NiO, alongside J sc of 21.80 mA cm −2 and FF of 0.78, resulting in an overall PCE of 19.89%. More than expected, the large hydrophobic groups at the interface as well as the grain boundaries tremendously enhanced the device ambient stability; our design of the graded layer not only enhanced moisture stability by abating water penetration but also improved thermal stability by suppressing the cross-layer ion migration. Figure 1A shows schematically the deposition method of the (CH 3 NH 3 PbI 3 -PEA 2 Pb 2 I 4 ) 3D-2D graded perovskite film. The deposition process is based on the solvent engineering method but with a key modification: [5] Phenethylammonium iodide (PEAI)/toluene solution was used instead of pure toluene for the solvent dripping process prior to conversion to a crystallized perovskite film by annealing at 95 °C. To facilitate comparison, three kinds of perovskite films were deposited under different conditions as shown in Table 1. In brief, the 3D-2D Graded sample was fabricated by the method mentioned above, while the 3D sample was deposited by the conventional toluene dripping process, and the 2D sample was made simply 2D halide perovskite materials have shown great advantages in terms of stability when applied in a photovoltaic device. However, the impediment of charge transport within the layered structure drags down the device performance. Here for the first time, a 3D-2D (MAPbI 3 -PEA 2 Pb 2 I 4 ) graded perovskite interface is demonstrated with synergistic advantages. In addition to the significantly improved ambient stability, this graded combination modifies the interface energy level in such a way that reduces interface charge recombination, leading to an ultrahigh V oc at 1.17 V, a record for NiO-based p-i-n photovoltaic devices. Moreover, benefiting from the graded structure induced continuously upshifts energy level, th...

NiO is a promising hole transporting material for perovskite solar cells due to its high hole mobility, good stability, easy processibility, and suitable Fermi level for hole extraction. However, the efficiency of NiO‐based cells is still limited by the slow hole extraction due to the poor perovskite/NiO interface and the inadequate quality of the two solution‐processed material phases. Here, large influences of a monolayer surface modification of NiO nanocrystal layers with ethanolamine molecules are demonstrated on the enhancement of hole extraction/transport and thus the photovoltaic performance. The underlying causes have been revealed by a series of studies, pointing to a favorable dipole layer formed by the molecular adsorption along with the enhanced perovskite crystallization and the improved interface contact. Comparatively, the solar cells based on a diethanolamine‐modified NiO layer have achieved a rather high fill factor, indeed one of the highest among NiO‐based perovskite solar cells, and high short‐circuit photocurrent density (Jsc), resulting in a power conversion efficiency of ≈16%, most importantly, without hysteresis.

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Our photoanode has achieved a record high photocurrent density and applied bias photon-to-current efficiency for BiVO4-based photoanodes.

We herein demonstrate the unusual effectiveness of two strategies in combination to enhance photoelectrochemical water splitting. First, the work function adjustment via molybdenum (Mo) doping significantly reduces the interfacial energy loss and increases the open-circuit photovoltage of bismuth vanadate (BiVO 4 ) photoelectrochemical cells. Second, the creation and optimization of the heterojunction of boron (B) doping carbon nitride (C 3 N 4 ) and Mo doping BiVO 4 to enforce directional charge transfer, accomplished by work function adjustment via B doping for C 3 N 4 , substantially boost the charge separation of photo-generated electron-hole pairs at the B-C 3 N 4 and Mo-BiVO 4 interface. The synergy between the above efforts have significantly reduced the onset potential, and enhanced charge separation and optical properties of the BiVO 4 -based photoanode, culminating in achieving a record applied bias photon-to-current efficiency of 2.67% at 0.54 V vs. the reversible hydrogen electrode. This work sheds light on designing and fabricating the semiconductor structures for the next-generation photoelectrodes.

Operational stability is one of the main obstacles that may hold back the commercialization of perovskite solar cells (PVSCs).