Electrochemical CO2 reduction is a key technology to recycle CO2 as a renewable resource, but adsorbing CO2 on the catalyst surface is challenging. We explored the effects of reduced graphene oxide (rGO) in Sn/rGO composites and found that the CO2 adsorption ability of Sn/rGO was almost 4-times higher than that of bare Sn catalysts. Density functional theory calculations revealed that the oxidized functional groups of rGO offered adsorption sites for CO2 toward the adjacent Sn surface and that CO2-rich conditions near the surface facilitated the production of formate via COOH* formation while suppressing CO* formation. Scanning electrochemical cell microscopy directly indicated that CO2 reduction was accelerated at the interface, together with the kinetic suppression of undesirable and competitive hydrogen evolution at the interface. Thus, the synergism of Sn/rGO ensures a substantial/rapid supply of CO2 from the functional groups to the Sn surface, thereby enhancing the Faradaic efficiency 1.8-times compared with that obtained with bare Sn catalysts.

Electrically conducting, continuous films of different phases of palladium selenides are synthesized by the thermolysis of single source molecular precursors. The films are found to be adherent on flat substrates such as glass, indium tin oxide and glassy carbon and are stable under electrochemical conditions. They are electrocatalytically active and in particular, for hydrogen evolution reaction. Catalytic activities with low Tafel slopes of 50-60 mV per decade are observed.

Identifying the influence of the phase of a catalyst on its reactivity is crucial for guiding the rational design of highly active electrocatalysts. Herein, we unveil the phasedependent reactivity of nickel molybdates (NiMoO 4 ) for the electrocatalytic urea oxidation reaction (UOR). Various NiMoO 4 phases, namely, α-NiMoO 4 , β-NiMoO 4 , and the hydrate NiMoO 4 •xH 2 O, were synthesized, and their structural characteristics and electrochemical properties were related to their electrocatalytic performance for the UOR. The NiMoO 4 phase was found to determine its reactivity, and phase-dependent UOR activities were observed. In particular, β-NiMoO 4 exhibited a higher activity and faster kinetics than NiMoO 4 •xH 2 O and α-NiMoO 4 , which was attributed to the large electrochemical surface area, low Tafel slope, and small charge− transfer resistance of β-NiMoO 4 . Moreover, hydrogen generation via β-NiMoO 4 -catalyzed urea electrolysis achieved a much lower cell voltage (1.498 V to reach 10 mA cm −2 ) than that required for water electrolysis (1.633 V to reach 10 mA cm −2 ). This work provides insights into design strategies for high-activity electrocatalysts for energy-efficient hydrogen production.

The increasing demand for conversion and storage of energy has been the driving force for scientific pursuits towards developing novel, highly active and selective materials.

Thin films of conducting, palladium selenide phases (Pd 17 Se 15 and Pd 7 Se 4 ) are prepared using a single source molecular precursor by thermolysis. Varying the mole ratios of palladium and selenium precursors results in palladium organo-selenolate complexes which on thermolysis at different temperatures yield Pd 17 Se 15 and Pd 7 Se 4 phases that are very stable and adherent to the substrate. The organo-selenolate complexes are characterized using small angle XRD, 77 Se NMR and thermogravimetric analysis (TGA). The palladium selenide films are characterized by various techniques such as XRD, XPS, TEM and SEM. Electrical conductivities of the films are determined using four probe method. The strong adherence of the films to glass substrates coupled with high corrosion resistant behavior towards strong acid and alkaline environments render them to be very effective as electrocatalysts. The catalytic activity towards I 3 -/Iredox couple, which is an important reaction in the regeneration of the dye in dye-sensitized solar cell is studied. Between the two phases, Pd 17 Se 15 film shows superior activity as counter electrode for dye sensitized solar cells with photocurrent conversion efficiency of 7.45%.