Single-atom catalysts provide an effective approach to reduce the amount of precious metals meanwhile maintain their catalytic activity. However, the sluggish activity of the catalysts for alkaline water dissociation has hampered advances in highly efficient hydrogen production. Herein, we develop a single-atom platinum immobilized NiO/Ni heterostructure (PtSA-NiO/Ni) as an alkaline hydrogen evolution catalyst. It is found that Pt single atom coupled with NiO/Ni heterostructure enables the tunable binding abilities of hydroxyl ions (OH*) and hydrogen (H*), which efficiently tailors the water dissociation energy and promotes the H* conversion for accelerating alkaline hydrogen evolution reaction. A further enhancement is achieved by constructing PtSA-NiO/Ni nanosheets on Ag nanowires to form a hierarchical three-dimensional morphology. Consequently, the fabricated PtSA-NiO/Ni catalyst displays high alkaline hydrogen evolution performances with a quite high mass activity of 20.6 A mg−1 for Pt at the overpotential of 100 mV, significantly outperforming the reported catalysts.

In this study, a general and effective phosphorization strategy is successfully demonstrated to enhance supercapacitor performance of various transition metals oxide or hydroxide, such as Ni(OH) 2 , Co(OH) 2 , MnO 2 , and Fe 2 O 3 . For example, a 3D networked Ni 2 P nanosheets array via a facile phosphorization reaction of Ni(OH) 2 nanosheets is grown on the surface of a Ni foam. The Ni foam-supported Ni 2 P nanosheet (Ni 2 P NS/NF) electrode shows a remarkable specifi c capacitance of 2141 F g −1 at a scan rate of 50 mV s −1 and remains as high as 1109 F g −1 even at the current density of 83.3 A g −1 . The specifi c capacitance is much larger than those of Ni(OH) 2 NS/NF (747 F g −1 at 50 mV s −1 ). Furthermore, the electrode retains a high specifi c capacitance of 1437 F g −1 even after 5000 cycles at a current density of 10 A g −1 , in sharp contrast with only 403 F g −1 of Ni(OH) 2 NS/NF at the same current density. The similar enhanced performance is observed for Ni 2 P powder, which eliminates the infl uence of nickel foam. The enhanced supercapacitor performances are attributed to the 3D porous nanosheets network, enhanced conductivity, and two active components of Ni 2+ and P δ − with rich valences of Ni 2 P.

Development of non-noble-metal catalysts for hydrogen evolution reaction (HER) with both excellent activity and robust stability has remained a key challenge in the past decades. Herein, for the first time, N-doped carbon-wrapped cobalt nanoparticles supported on N-doped graphene nanosheets were prepared by a facile solvothermal procedure and subsequent calcination at controlled temperatures. The electrocatalytic activity for HER was examined in 0.5 M H2SO4. Electrochemical measurements showed a small overpotential of only −49 mV with a Tafel slope of 79.3 mV/dec. Theoretical calculations based on density functional theory showed that the catalytically active sites were due to carbon atoms promoted by the entrapped cobalt nanoparticles. The results may offer a new methodology for the preparation of effective catalysts for water splitting technology.

Advanced materials for electrocatalytic water splitting are central to renewable energy research. In this work, three-dimensional (3D) hierarchical frameworks based on the self-assembly of MoS2 nanosheets on graphene oxide were produced via a simple one-step hydrothermal process. The structures of the resulting 3D frameworks were characterized by using a variety of microscopic and spectroscopic tools, including scanning and transmission electron microscopies, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman scattering. Importantly, the three-dimensional MoS2/graphene frameworks might be used directly as working electrodes which exhibited apparent and stable electrocatalytic activity in hydrogen evolution reaction (HER), as manifested by a large cathodic current density with a small overpotential of -107 mV (-121 mV when loaded on a glassy-carbon electrode) and a Tafel slope of 86.3 mV/dec (46.3 mV/dec when loaded on a glassy-carbon electrode). The remarkable performance might be ascribed to the good mechanical strength and high electrical conductivity of the 3D frameworks for fast charge transport and collection, where graphene oxide provided abundant nucleation sites for MoS2 deposition and oxygen incorporation led to the formation of defect-rich MoS2 nanosheets with active sites for HER.

Advanced materials for electrocatalytic water splitting are central to renewable energy research. In this work, MoS2 nanosheets supported on porous metallic MoO2 (MoS2/MoO2) were produced by sulfuration treatments of porous and highly conductive MoO2 for the hydrogen evolution reaction. Porous MoO2 with one-dimensional channel-like structures was prepared by calcination at elevated temperatures using phosphomolybdic acid as the precursor and mesoporous silica (SBA-15) as the template, and the subsequent hydrothermal treatment in the presence of thioacetamide led to the transformation of the top layers to MoS2 forming MoS2/MoO2 composites. Electrochemical studies showed that the obtained composites exhibited excellent electrocatalytic activity for HER with an onset potential of -104 mV (vs. RHE), a large current density (10 mA cm(-2) at -0.24 V), a small Tafel slope of 76.1 mV dec(-1) and robust electrochemical durability. The performance might be ascribed to the high electrical conductivity and porous structures of MoO2 with one-dimensional channels of 3 to 4 nm in diameter that allowed for fast charge transport and collection.

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Core–shell nanocomposites based on Au nanoparticle@zinc–iron-embedded porous carbons (Au@Zn–Fe–C) derived from metal–organic frameworks were prepared as bifunctional electrocatalysts for both oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). A single Au nanoparticle of 50–100 nm in diameter was encapsulated within a porous carbon shell embedded with Zn–Fe compounds. The resulting Au@Zn–Fe–C hybrids exhibited apparent catalytic activity for ORR in 0.1 M KOH (with an onset potential of +0.94 V vs RHE, excellent stability and methanol tolerance) and for HER as well, which was evidenced by a low onset potential of −0.08 V vs RHE and a stable current density of 10 mA cm–2 at only −0.123 V vs RHE in 0.5 M H2SO4. The encapsulated Au nanoparticles played an important role in determining the electrocatalytic activity for ORR and HER by promoting electron transfer to the zinc–iron-embedded porous carbon layer, and the electrocatalytic activity was found to vary with both the loading of the gold nanoparticle cores and the thickness of the metal–carbon shells. The experimental results suggested that metal-embedded porous carbons derived from metal–organic frameworks might be viable alternative catalysts for both ORR and HER.