Facile electrolysis-solvothermal synthesis of NiOx/graphene for enhanced ethanol oxidation to acetate.

In this work, low-crystalized and defective NiOx/graphene was synthesized by a facile electrolysis-solvothermal method. In the electrolytic process, Ni ions originate from the Ni anode, and graphene is produced from the graphite cathode. Then, Ni ions are reduced into oxides and deposited on graphene in the subsequent solvothermal process. The NiOx/graphene displays excellent electrocatalytic activity and selectivity for ethanol oxidation reaction to acetate. The peak current density was 296.5 mA cm-2 on a glassy carbon electrode. The FE of acetate was more than 93% at the potential range between 1.4 and 1.7 V. We propose that the mechanism is a cooperation between the chemical deprotonating process of ethanol by Ni3+ species and the electrochemical oxidation of the CH3CH2O* intermediate to acetate at the interface between NiOx and graphene.

Interfacial carbon dots introduced distribution-structure modulation of Pt loading on graphene towards enhanced electrocatalytic hydrogen evolution reaction.

To easily load Pt on smoothy graphene synthesized by cathodic exfoliation method and achieve adjacent plane distribution of Pt, carbon dots (CDs) are used to construct anchoring points to load highly dispersed Pt species due to strong interaction between CDs and Pt species. The composite of Pt-CDs/graphene is synthesized via a continuous process of cathodic exfoliation-hydrothermal-impregnation-reduction. Characterization results indicate the distribution configuration of Pt varies from coated structure of CDs@Pt to dispersed configuration of CDs&Pt or Pt&CDs, then to wrapping configuration of Pt@CDs with increased amount of CDs. It's found that suitable introduction of CDs promotes the adjacent plane distribution of Pt species. The obtained best Pt-4CDs/G shows the low overpotential of 36 mV (10 mA⋅cm-2) and high mass activity of 3747.8 mA mg-1 at -40 mV towards electrocatalytic hydrogen evolution reaction (HER), 9.2 times more active than that of Pt/C (406.2 mA mg-1). The superior HER performance of Pt-4CDs/G is attributed to its relatively adjacent plane distribution of Pt, which supports high electrochemically active surface area and more adjacent Pt sites for H* adsorption. Benefitting from that, the HER process for Pt-4CDs/G favorably follows the Tafel pathway, resulting in low hydrogen adsorption free energy and excellent HER activity.