Direct loading of plasmonic nanostructures onto catalytically inert conductive support materials leads to the Schottky barrier-free architecture of the photocatalytic system. Such systems have recently attracted the attention of the research community as they permit collection of hot carriers independent of their energy when additional charge separation strategies are used. However, a systematic mechanistic investigation and description of the contribution of an inert conductive support to plasmonic electrocatalysis is missing. Herein, we systematically investigated the effect of the supporting electrode material on the observed photoinduced enhancement by comparing the photoelectrocatalytic properties of AuNPs supported on highly oriented pyrolytic graphite (HOPG) and indium tin oxide (ITO) electrodes using electrocatalytic benzyl alcohol (BnOH) oxidation as a model system. Upon illumination, only ∼(3 ± 1)% enhancement in catalytic current was recorded on the AuNP/ITO electrodes in contrast to ∼(42 ± 6)% enhancement on AuNP/HOPG electrodes. Our results showed that the local heating due to light absorption by the electrode material itself independent of localized surface plasmon effects is the primary source of the observed significant photoinduced enhancement on the HOPG electrodes in comparison to the ITO electrodes. Moreover, we demonstrated that an increased interfacial charge transfer at elevated temperatures and not faster reactant diffusion as suggested previously is the main source of the thermal enhancement. This work highlights the importance of the systematic evaluation of contributions of all parts, even if they are catalytically inert, to the light-induced facilitation of catalytic reactions in plasmonic systems.

Understanding the effect of molybdate incorporation on the structure, morphology, porosity, surface area and etching-induced enhanced electrocatalytic water splitting of low-cost transition metal hydroxides grown on inexpensive copper substrate.

Despite predictions of high electrocatalytic OER activity by selenide-rich phases, such as NiCo 2 Se 4 and Co 3 Se 4 , their synthesis through a wet-chemical route remains a challenge because of the high sensitivity of the various oxidation states of selenium to the reaction conditions. In this work, we have determined the contribution of individual reactants behind the maintenance of conducive solvothermal reaction conditions to produce phase-pure NiCo 2 Se 4 and Co 3 Se 4 from elemental selenium. The maintenance of reductive conditions throughout the reaction was found to be crucial for their synthesis, as a decrease in the reductive conditions over time was found to produce nickel/cobalt selenites as the primary product. Further, the reluctance of Ni(II) to oxidize into Ni(III) in comparison to the proneness of Co(II) to Co(III) oxidation was found to have a profound effect on the final product composition, as a deficiency of ions in the III oxidation state under nickel-rich reaction conditions hindered the formation of a monoclinic "Co 3 Se 4 -type" phase. Despite its lower intrinsic OER activity, Co 3 Se 4 was found to show geometric performance on a par with NiCo 2 Se 4 by virtue of its higher textural and microstructural properties.

Developing electrocatalysts with abundant active sites is a substantial challenge to reduce the overpotential requirement for the alkaline oxygen evolution reaction (OER). In this work, we have aimed to improve the catalytic activity of cobalt selenides by growing them over the self-supported Co3O4 microrods. Initially, Co3O4 microrods were synthesized through annealing of an as-prepared cobalt oxalate precursor. The subsequent selenization of Co3O4 resulted in the formation of a grainy rodlike Co3O4/Co0.85Se/Co9Se8 network. The structural and morphological analysis reveals the presence of Co3O4 even after the selenization treatment where the cobalt selenide nanograins are randomly covered over the Co3O4 support. The resultant electrode shows superior electrocatalytic activity toward OER in alkaline medium by delivering a benchmark current density of 10 mA/cm2 geo at an overpotential of 330 mV. As a comparison, we have developed Co0.85Se/Co9Se8 under similar conditions and evaluated its OER activity. This material consumes an overpotential of 360 mV to deliver the benchmark current density, which signifies the role of the Co3O4 support to improve the electrocatalytic activity of Co0.85Se/Co9Se8. Despite having a low TOF value for Co3O4/Co0.85Se/Co9Se8 (0.0076 s–1) compared to Co0.85Se/Co9Se8 (0.0102 s–1), the improved catalytic activity of Co3O4/Co0.85Se/Co9Se8 is attributed to the presence of a higher number of active sites rather than the improved per site activity. This is further supported from the C dl (double layer capacitance) measurements where Co3O4/Co0.85Se/Co9Se8 and Co0.85Se/Co9Se8 tender C dl values of about 8.19 and 1.08 mF/cm2, respectively, after electrochemical precondition. As-prepared Co3O4/Co0.85Se/Co9Se8 also manifests rapid kinetics (low Tafel slope ∼ 91 mV/dec), long-term stability, low charge-transfer resistance, and 82% Faradaic efficiency for alkaline electrocatalysis (pH = 14). Furthermore, the proton reaction order (ρRHE) is found to be 0.65, indicating a proton decoupled electron transfer (PDET) mechanism for alkaline OER. Thus, the Co3O4 support helps in the exposure of more catalytic sites of Co0.85Se/Co9Se8 to deliver the improved catalytic activities in alkaline medium.

The electrocatalytic oxygen evolution reaction (OER) demands an efficient catalyst with low overpotential, rapid kinetics, and long-term stability. Herein, we demonstrate the activity of molybdenum oxide (MoO 2 )-embedded cobalt oxalate (CoC 2 O 4 • 2H 2 O) nanostructures for the OER process. The excellent performance of the microrod-like MoO 2 /CoC 2 O 4 •2H 2 O composite is reflected in just 330 mV overpotential for 10 mA/cm geo 2 , low Tafel slope (78 mV/dec), 90% faradaic efficiency, and 24 h stability in 1.0 (M) KOH. The as-prepared electrocatalyst requires a significantly lower overpotential wrt CoC 2 O 4 •2H 2 O. Incorporation of MoO 2 elegantly modified the textural property, such as surface area and porosity, of the as-prepared material. Furthermore, MoO 2 / CoC 2 O 4 •2H 2 O was found to follow the proton-decoupled electrontransfer mechanism for electrocatalyzing OER. Postcatalytic characterization revealed the electrochemical transformation of a one-dimensional (1-D) MoO 2 /CoC 2 O 4 •2H 2 O microrod into a sheetlike two-dimensional α-Co(OH) 2 /CoOOH during alkaline OER. Interestingly, postcatalytic X-ray photoelectron spectroscopy, inductively coupled plasma, and energy-dispersive X-ray spectroscopy analyses suggest MoO 2 etching from the material, leading to exposure of a higher number of electrochemically active sites that otherwise lay inactive because of their presence in the bulk. Both CoC 2 O 4 •2H 2 O-and MoO 2 /CoC 2 O 4 •2H 2 O-integrated 1-D nanostructures showed an ∼0.01 s −1 turnover frequency value at 400 mV overpotential.We believe that the enhancement in geometrical electrocatalytic activity is not due to the direct participation of MoO 2 in catalysis but due to its electrochemical etching, which makes a higher number of catalytically active sites accessible to the electrolyte. This study conveys the in situ electrochemical activation strategy through etching of pore additive for the alkaline OER process.