Dinitrogen Reduction Coupled with Methanol Oxidation for Low Overpotential Electrochemical NH3 Synthesis Over Cobalt Pyrophosphate as Bifunctional Catalyst

Real-time screening of NixBy bifunctional electrocatalysts for overall NH3 synthesis via SG-TC SECM

Electrochemical ammonia synthesis, which couples oxygen evolution at the anode with nitrogen reduction at the cathode, holds great significance for future food and energy needs. Both of these half-cell reactions determine the overall cell potential and efficiency of the process. However, the employment of different catalysts on either side, due to discrete mechanisms, increases the complexity and material processing costs of the system, where the designing of a bifunctional catalyst active towards both the NRR and OER is of huge significance. Unfortunately, the initial screening of the designed catalysts via physical characterizations, optical methods and other techniques, does not provide details about the electrochemical activity. The scanning electrochemical microscopy (SECM) technique can be useful to screen multi-catalysts at the same time for their electrochemical activities. Herein, we employed the sample generation-tip collection (SG-TC) mode of SECM to screen the designed NixBy catalysts before half-cell investigations, which suggested that the catalyst synthesized via sonochemical reduction (SR), i.e. NixBy (SR), was a better catalyst. This inference was in accordance with the half-cell NRR and OER measurements (FE: 49% for NH3 production, OER overpotential: 300 mV). By virtue of this remarkable bifunctional activity, the NRR-OER coupled full cell was assembled, which initiated the NH3 production at just 1.7 V and produced NH3 (1.08 mg h-1 mgcat-1) at the cathode and O2 (0.81 mg h-1 mgcat-1) at the anode after 2 h of electrolysis at 1.9 V.

Boosting nucleophilic attack to realize high current density biomass valorization on a tunable Prussian blue analogue

Electrochemical biomass valorization provides a promising approach to generating value-added chemicals. Herein, we have creatively utilized a Prussian blue analogue as a structure template of the anodic catalyst and improved its catalyst capacity by adjusting its electronic structure. The nickel-based Prussian blue analogue/Ni foam (NiFe-PBA/NF) exhibits excellent performance for methanol (MeOH) oxidation and achieves almost 94.1% FE of formic acid at a high current density of 500 mA cm-2. Apart from formic acid, NiFe-PBA/NF also has good catalytic ability for ethanol, glycerol, glucose, and 5-hydroxymethylfurfural (HMF). In short, this work has developed a promising class of catalysts for biomass valorization.