Hydrogen evolution electrocatalysts can achieve sustainable hydrogen production via electrocatalytic water splitting; however, designing highly active and stable noble‐metal‐free hydrogen evolution electrocatalysts that perform as efficiently as Pt catalysts over a wide pH range is a challenging task. Herein, a new 2D cobalt phosphide/nickelcobalt phosphide (CoP/NiCoP) hybrid nanosheet network is proposed, supported on an N‐doped carbon (NC) matrix as a highly efficient and durable pH‐universal hydrogen evolution reaction (HER) electrocatalyst. It is derived from topological transformation of corresponding layer double hydroxides and graphitic carbon nitride. This 2D CoP/NiCoP/NC catalyst exhibits versatile HER electroactivity with very low overpotentials of 75, 60, and 123 mV in 1 m KOH, 0.5 m H2SO4, and 1 m PBS electrolytes, respectively, delivering a current density of 10 mA cm−2 for HER. Such impressive HER performance of the hybrid electrocatalyst is mainly attributed to the collective effects of electronic structure engineering, strong interfacial coupling between CoP and NiCoP in heterojunction, an enlarged surface area/exposed catalytic active sites due to the 2D morphology, and conductive NC support. This method is believed to provide a basis for the development of efficient 2D electrode materials with various electrochemical applications.

In this contribution we have developed TiO inverse opal based photoelectrodes for photoelectrochemical (PEC) water splitting devices, in which Au nanoparticles (NPs) and reduced graphene oxide (rGO) have been strategically incorporated (TiO@rGO@Au). The periodic hybrid nanostructure showed a photocurrent density of 1.29 mA cm at 1.23 V vs RHE, uncovering a 2-fold enhancement compared to a pristine TiO reference. The Au NPs were confirmed to extensively broaden the absorption spectrum of TiO into the visible range and to reduce the onset potential of these photoelectrodes. Most importantly, TiO@rGO@Au hybrid exhibited a 14-fold enhanced PEC efficiency under visible light and a 2.5-fold enrichment in the applied bias photon-to-current efficiency at much lower bias potential compared with pristine TiO. Incident photon-to-electron conversion efficiency measurements highlighted a synergetic effect between Au plasmon sensitization and rGO-mediated facile charge separation/transportation, which is believed to significantly enhance the PEC activity of these nanostructures under simulated and visible light irradiation. Under the selected operating conditions the incorporation of Au NPs and rGO into TiO resulted in a remarkable boost in the H evolution rate (17.8 μmol/cm) compared to a pristine TiO photoelectrode reference (7.6 μmol/cm). In line with these results and by showing excellent stability as a photoelectrode, these materials are herin underlined to be of promising interest in the PEC water splitting reaction.

A facile and elegant methodology invoking the principles of Green Chemistry for the synthesis of porous tin dioxide nanospheres has been described. The low-temperature (∼50 °C) synthesis of SnO₂ nanoparticles and their self-assembly into organized, uniform, and monodispersed porous nanospheres with high surface area is facilitated by controlling the concentration of glucose, which acts as a stabilizing as well as structure-directing agent. A systematic control on the stannate to glucose molar concentration ratio determines the exact conditions to obtain monodispersed nanospheres, preferentially over random aggregation. Detailed characterization of the structure, morphology, and chemical composition reveals that the synthesized material, 50 nm SnO₂ porous nanospheres possess BET surface area of about 160 m²/g. Each porous nanosphere consists of a few hundred nanoparticles ∼2-3 nm in diameter with tetragonal cassiterite crystal structure. The SnO₂ nanospheres exhibit elevated photocatalytic activity toward methyl orange with good recyclability. Because of the high activity and stability of this photocatalyst, the material is ideal for applications in environmental remediation. Moreover, SnO₂ nanospheres display excellent gas sensing capabilities toward hydrogen. Surface modification of the nanospheres with Pd transforms this sensing material into a highly sensitive and selective room-temperature hydrogen sensor.

This study reports on the formation of unique oriented ZnO structures (face oriented hexagonal discs, 3D-trapezoids, rings, doughnuts, and hemispheres) with tunable percentage of exposed polar facets synthesized via a simple hydrothermal route in aqueous base environment. The significance of the synthetic strategy is the generation of exotic structures without using any templates/structure directing agents and successful realization of morphologies with increased polar to nonpolar facet ratio. Detailed investigation reveals that the size and shape of ZnO microstructures can be conveniently tailored by systematically exercising control on the choice of precursor (zinc source), concentration of reactants, use of Trizma as a base (pH control) which is also seen as structure directing agent. The Trizma base with an appreciably short pH range effectively controls the rate of hydrolysis, regulates nucleation, and restrains rapid growth leading to these well-defined ZnO structures. Photocatalytic degradation of methylene blue as a model system was used to showcase the morphology-dependent enhanced photoactivity under UV-light. The enhanced photocatalytic performance could be attributed to the higher fraction of exposed (0001) and (0001̅) ZnO polar facets present.