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Unique 2D ternary hierarchitectures constructed from reduced graphene oxide nanosheets grown with ultrathin Cd0.15Zn0.85In2S4 nanosheets and Ni2P nanoparticles exhibited an outstanding capability for visible-light photocatalytic H2 production.

Unique Cd0.5Zn0.5S/WO3−x direct Z-scheme heterojunction with S, O vacancies and zinc blende/wurtzite twinning superlattices exhibited a dramatically heightened capability toward visible-light photocatalytic H2 generation.

Although intensive efforts have been made and great progress has been achieved relating to the electrocatalytic hydrogen evolution reaction (HER), an advanced synthesis strategy for an efficient electrocatalyst is still the most significant goal. In this paper, we introduce PdFeCoNiCu high-entropy alloy (HEA) nanoparticles as an efficient electrocatalyst for the HER, which has been prepared in an oil phase under facile conditions for the first time. PdFeCoNiCu/C shows excellent alkaline HER catalytic performance with an overpotential of only 18 mV and a Tafel slope of 39 mV dec−1. Meanwhile, we achieved the highest mass activity (6.51 A mgPd−1 at −0.07 V vs. RHE) in the alkaline HER among all non-Pt electrocatalysts. PdFeCoNiCu/C also shows surprisingly stable catalytic properties for over 15 days without notable decay. Based on theoretical calculations, the HEA surface demonstrates the optimization of electronic structures based on a synergistic effect between all metals. Pd and Co are confirmed to be the dominant electroactive sites for both H2 formation and initial water splitting, which are assisted by Ni, Fe, and Cu promotion, enhancing electron transfer and optimizing the binding energies of hydrogen intermediates. This work has supplied significant insight into the design of an efficient electrocatalyst based on HEA materials.

Two-dimensional (2D) semiconductor nanostructures have exhibited great prospect as an efficient photocatalyst for solar-to-fuel application. In this work, a unique 2D tandem heterojunction consisting of ultrathin CdxZn1−xIn2S4 nanosheets coupled with rectangular CdS flakes and defect-rich MoS2 few-layered nanosheets was constructed for the first time. Remarkably, the efficient electron transfer channels present in the CdS/CdxZn1−xIn2S4 and CdxZn1−xIn2S4/MoS2 2D tandem heterojunctions facilitate the spatial separation and directional migration of photo-induced charge carriers effectively. Moreover, such 2D tandem heterojunction CdxZn1−xIn2S4–CdS–MoS2 is provided with excellent light harvesting capacity and abundant HER active sites from the defective MoS2 co-catalyst. These distinct advantages endow the optimized C0.15ZIS–5C–3M hybrid (5 wt% CdS, 3 wt% MoS2) with an exceptional photocatalytic H2 evolution reaction (HER) activity of 27.14 mmol h−1 g−1, approximately 47 times that of pure ZnIn2S4 and it is much superior to that of Pt-decorated C0.15ZIS–5C and most ZnIn2S4-based composites reported previously. A high HER apparent quantum yield (AQY) of 19.97% is achieved at λ = 400 nm. In addition, both the cycling and long-term HER measurements evidence the prominent stability of C0.15ZIS–5C–3M for H2 production. The results indicated here could pave the way for the exploitation of new 2D heterostructures toward highly-efficient solar conversion and utilization.

A heterogeneous structure formed by coupling two or more phases can reinforce the activity of active sites and expedite electron transfer, which is conducive to boosting its electrocatalytic activity. Herein, we designed nickel foam supported (NiCo2)Se@Ni(OH)2 (NCS@NH) heterojunction nanosheets by a two-step method. First of all, the NiCo2S4@Ni(OH)2 (NiCo2S4@NH) nanosheets coated on nickel foam were acquired via a hydrothermal method. In the selenization treatment that followed, NiCo2S4@NH was converted into NCS@NH heterogeneous nanosheets in which the selenide nanoparticles decorated on the surface of the Ni(OH)2 nanosheets formed heterojunction interfaces, and the heterogeneous structure could accelerate electron transfer, thus improving the catalytic activity. The Ni(OH)2 nanosheets can adequately contact the electrolyte and promote the decomposition of water. Meanwhile, the thickness of the Ni(OH)2 nanosheets gradually decreases with the increase of Co doping (1.5-2.5 mmol), consequently affecting the HER properties. Notably, when the amount of Co salt added is 2 mmol, NCS@NH exhibited superior HER properties (with a voltage of 253 mV at 100 mA cm-2) and excellent stability for 24 h.

As ammonia is an important chemical raw material, a lot of efforts have been made in the field of electrochemical nitrogen reduction (NRR) to promote artificial nitrogen fixation. At present, research on NRR is widely focused on improving the catalyst's adsorption and activation of N2. However, it has not yet been studied how to promote the desorption of NH3 by the catalyst to obtain continuous and stable catalytic activity. Herein, we synthesized Pd octahedrons and icosahedrons with similar sizes and studied the role of twins in NRR for the first time. At −0.2 V vs. RHE, the Pd icosahedron achieved a high NH3 yield and FE, which were 17.56 μg h−1 cm−2 (43.9 μg h−1 mgcat.−1) and 31.98%, respectively. After 200 h of electrolysis, the NH3 yield of Pd icosahedrons did not significantly decrease, which maintained excellent catalytic stability. Its performance is better than other catalysts that have been reported. In situ FTIR measurements and DFT calculation proved that due to the existence of the twin structure, the energy required for the potential-determining step and the NH3 desorption step of the Pd catalyst is greatly reduced. Accelerating the desorption of NH3 improves the utilization of active sites due to which the Pd icosahedron maintains continuous excellent catalytic activity. This provides a new direction for the design of catalysts to improve their NRR performance.

NC@Co-HPNC is synthesized, which exhibits a superior ORR/OER performance in acid/base solution. Hence, acid-base dual-electrolyte-based Zn-air batteries using NC@Co-HPNC reveal a long cycling life and a super-high voltage (2.1 V).

Rechargeable Li–O2 batteries have attracted worldwide attention due to their super-high energy density. However, there are still many critical challenges for Li–O2 batteries, such as huge overpotential caused by sluggish oxygen reduction/evolution reaction (ORR/OER) kinetics, and inferior cycle life derived from severe side reactions. Designing highly efficient cathode catalysts should be a good choice for Li–O2 batteries to solve the above problems. Herein, we developed Ir-coated Co nanoparticles confined into highly porous N-doped carbon nanocubes grafted with carbon nanotubes (Ir–Co/HP-NC/CNT) through carbonization of the Co/Zn–zeolitic imidazolate framework (ZIF) and the subsequent Ir-coating. Introduction of Zn into the ZIF precursor not only makes Ir–Co/HP-NC/CNT have high porosity that can promote ion/electron transfer, but also improves the surface content of pyridinic/graphitic N and CoxN phases which accelerate ORR/OER kinetics. Moreover, theoretical calculation/experimental results further confirm that the synergy between the Ir-coating and Co/HP-NC/CNT can effectively alleviate undesired parasitic reactions and also enhance reversibility in Li–O2 batteries by adjusting Li2O2 formation. As a result, Ir–Co/HP-NC/CNT based Li–O2 batteries show a super-high discharge capacity of 13 200 mA h g−1 at 100 mA g−1 and a very long cycling life up to 320 cycles at 500 mA g−1 with a fixed capacity of 1000 mA h g−1. Importantly, we have also designed large-size bulk-shaped Li–air batteries with Ir–Co/HP-NC/CNT cathodes that exhibit good performance even under bending conditions and effectively power practical electronic devices.

Improving the performance of catalysts by adjusting the vacancy engineering is currently one of the main ways to design effective catalysts. However, there are no reports in the literature on the influence that fluorine vacancies (FVs) have on the electronic structures of materials. In this work, we report the generation of FVs for the first time and discuss in depth their regulation mechanism on materials and their role in the electrochemical N2 reduction reaction (NRR). The catalyst optimized by FVs showed good NRR performance in Li2SO4 solution. At 0 V vs. RHE, the faradaic efficiency (FE) reaches the highest value of 36.01%. When the potential is increased to −0.10 V vs. RHE, the highest ammonia yield is 7.99 μg h−1 cm−2. The specific activity of the FV-optimized LaF3 nanosheets (NSs) is 9.5 times higher than that of the defect-free LaF3 NSs. It is currently reported as the most effective non-noble metal catalyst in the nitrogen reduction process under low overpotential. In addition, this catalyst also demonstrates long-term structural stability. In situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and density functional theory (DFT) show that the LaF3 NSs with the optimal defects have a multi-step promoting effect.

Transitional bimetallic sulfides have attracted extensive attention for electrocatalytic hydrogen evolution owing to their abundant reserves and low price. However, the rational design and the controlled synthesis of transitional bimetallic sulfide-based electrocatalysts for hydrogen production is still a big challenge. In this work, we report the synthesis of V-doped MoS2-NixSy/NF (VMNS/NF-β, β = nV : nMo) hollow nanospheres by an in situ one-pot method, and the electrocatalytic performance of the nanospheres can be optimized by adjusting the amount of vanadium doping. The introduction of the V source and Mo source can promote the formation of typical hollow nanospheres and affect the crystal phases of NiS. V has the advantages of valence diversity and unique electronic structure as well as the synergistic effect of bimetallic sulfide to enhance the electrocatalytic performance of the whole system. The optimized VMNS/NF (nV : nMo = 1 : 1) showed excellent HER performance in 1 M KOH solution at room temperature. At the current density of 10 mA cm−2, it has a low overpotential of 68 mV and maintains good stability at a current density of 32 mA cm−2 for 24 h.

The catalytic properties of non-noble metal catalysts are not comparable to those of noble metal catalysts, such as Pt and Ru, on account of the catalytic thresholds of these non-noble metal catalysts. In order to solve this problem, an efficient P, W-MoS2/NiSP/NF catalyst was rationally designed through heteroatom (P and W) doping and heterostructure construction. Interestingly, motivated by the synergistic incorporation of W and P, the 2H-phase MoS2 with limited edge active sites was partially converted into highly active 1T-phase MoS2 with rich defects, which basically activate the hydrogen evolution reaction (HER)-inert basal plane of MoS2 and significantly enlarge the number of active sites, ultimately endowing the well-designed P, W-MoS2/NiSP/NF catalyst with Pt-like HER performance and superior oxygen evolution reaction (OER) performance. Importantly, this work exerts a profound influence on the construction of 1T-MoS2 with defects, the design of multi-stage structures, and the achievement of Pt-like catalytic performance.