Overpotential

About: Overpotential is a research topic. Over the lifetime, 16474 publications have been published within this topic receiving 616632 citations.

Efficient Electrochemical Reduction of Carbon Dioxide to Acetate on Nitrogen-Doped Nanodiamond

Abstract: Electrochemical reduction of CO2 is an attractive technique for reducing CO2 emission and converting it into useful chemicals, but it suffers from high overpotential, low efficiency or poor product selectivity. Here, N-doped nanodiamond/Si rod array (NDD/Si RA) was proposed as an efficient nonmetallic electrocatalyst for CO2 reduction. It preferentially and rapidly converted CO2 to acetate over formate with an onset potential of −0.36 V (vs RHE), overcoming the usual limitation of low selectivity for C2 products. Moreover, faradic efficiency of 91.2–91.8% has been achieved for CO2 reduction at −0.8 to −1.0 V. Its superior performance for CO2 reduction can be attributed to its high overpotential for hydrogen evolution and N doping, where N-sp3C species was highly active for CO2 reduction. Electrokinetic data and in situ infrared spectrum revealed the main pathway for CO2 reduction might be CO2 → CO2•– → (COO)2• → CH3COO–.

Pd-Catalyzed Electrohydrogenation of Carbon Dioxide to Formate: High Mass Activity at Low Overpotential and Identification of the Deactivation Pathway

Abstract: Electrochemical reduction of CO2 to formate (HCO2–) powered by renewable electricity is a possible carbon-negative alternative to synthesizing formate from fossil fuels. This process is energetically inefficient because >1 V of overpotential is required for CO2 reduction to HCO2– on the metals currently used as cathodic catalysts. Pd reduces CO2 to HCO2– with no overpotential, but this activity has previously been limited to low synthesis rates and plagued by an unidentified deactivation pathway. Here we show that Pd nanoparticles dispersed on a carbon support reach high mass activities (50–80 mA HCO2– synthesis per mg Pd) when driven by less than 200 mV of overpotential in aqueous bicarbonate solutions. Electrokinetic measurements are consistent with a mechanism in which the rate-determining step is the addition of electrochemically generated surface adsorbed hydrogen to CO2 (i.e., electrohydrogenation). The electrodes deactivate over the course of several hours because of a minor pathway that forms CO. ...

Ni3+-Induced Formation of Active NiOOH on the Spinel Ni–Co Oxide Surface for Efficient Oxygen Evolution Reaction

Abstract: Efficient and earth abundant electrocatalysts for high-performance oxygen evolution reaction (OER) are essential for the development of sustainable energy conversion technologies. Here, a new hierarchical Ni–Co oxide nanostructure, composed of small secondary nanosheets grown on primary nanosheet arrays, is synthesized via a topotactic transformation of Ni–Co layered double hydroxide. The Ni3+-rich surface benefits the formation of NiOOH, which is the main redox site as revealed via in situ X-ray absorption near edge structure and extended X-ray absorption fine structure spectroscopy. The Ni–Co oxide hierarchical nanosheets (NCO–HNSs) deliver a stable current density of 10 mA cm−2 at an overpotential of ≈0.34 V for OER with a Tafel slope of as low as 51 mV dec−1 in alkaline media. The improvement in the OER activity can be ascribed to the synergy of large surface area offered by the 3D hierarchical nanostructure and the facile formation of NiOOH as the main active sites on the surface of NCO–HNSs to decrease the overpotential and facilitate the catalytic reaction.