Electrochemical Raman spectroscopy is a powerful molecular level diagnostic technique for in situ investigation of adsorption and reactions on various material surfaces. However, there is still a big room to improve the optical path to meet the increasing request of higher detection sensitivity and spatial resolution. Herein, we proposed a novel electrochemical Raman setup based on a water immersion objective. It dramatically reduces mismatch of the refractive index in the light path. Consequently, significant improvement in detection sensitivity and spatial resolution has been achieved from both Zemax simulation and the experimental results. Furthermore, the thickness of electrolyte layer could be expanded to 2 mm without any influence on the signal collection. Such a thick electrolyte layer allows a much normal electrochemical response during the spectroelectrochemical investigations of the methanol oxidation.

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Electrocarboxylation of organic compounds with CO2, using electrons as clean reductants under ambient conditions, is a readily available and efficient method to transform organic molecules to high‐value carboxylates with nearly 100% atom efficiency. However, the selectivity of the electrochemical reactions is still limited, the real reactive sites for electrocarboxylation; the relationship between the geometrical/electronic structure and the catalytic performance is unclear. Meanwhile, the development of nanomaterials brings new prospects and orientation for the electrocarboxylation due to the desired high surface area and abundant active sites. In this review, we focus on the summary of recent work on the design of nanostructured electrocatalysts and the reaction mechanisms of electrocarboxylation. Mainly, we highlight the influence of different electrocatalyst structures on a variety of organic molecule adsorption. Finally, some challenges were proposed to explore advanced electrocatalysts and the deeper reactive mechanism for electrocarboxylation.

Formate can be synthesized electrochemically by CO2 reduction reaction (CO2RR) or formaldehyde oxidation reaction (FOR). The CO2RR approach suffers from kinetic-sluggish oxygen evolution reaction at the anode. To this end, an electrochemical system combining cathodic CO2RR with anodic FOR was developed, which enables the formate electrosynthesis at ultra-low voltage. Cathodic CO2RR employing the BiOCl electrode in H-cell exhibited formate Faradaic efficiency (FE) higher than 90% within a wide potential range from − 0.48 to − 1.32 VRHE. In flow cell, the current density of 100 mA cm−2 was achieved at − 0.67 VRHE. The anodic FOR using the Cu2O electrode displayed a low onset potential of − 0.13 VRHE and nearly 100% formate and H2 selectivity from 0.05 to 0.35 VRHE. The CO2RR and FOR were constructed in a flow cell through membrane electrode assembly for the electrosynthesis of formate, where the CO2RR//FOR delivered an enhanced current density of 100 mA cm−2 at 0.86 V. This work provides a promising pair-electrosynthesis of value-added chemicals with high FE and low energy consumption.

The electrooxidation of 5-hydroxymethylfurfural (HMF) offers a promising green route to attain high-value chemicals from biomass. The HMF electrooxidation reaction (HMFOR) is a complicated process involving the combined adsorption and coupling of organic molecules and OH- on the electrode surface. An in-depth understanding of these cooperative adsorption behaviors and reaction processes is fundamentally essential. Herein, the adsorption behavior of HMF and OH-, and the role of oxygen vacancy on Co3O4 are initially unraveled. Correspondingly, instead of the competitive adsorption of OH- and HMF on the metal sites, it is observed that the OH- could fill into oxygen vacancy (Vo) before couple with organic molecules through the lattice oxygen oxidation reaction process, which could accelerate the rate-determining step of the dehydrogenation of 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) and enhance the overall conversion of HMF on Vo-Co3O4. This work sheds a depth insight on the catalytic mechanism of oxygen vacancy, which benefits designing a novel strategy to modulate the multi-molecules combined adsorption behaviors.