Designing and fabricating the electrocatalysts is attracting more and more attention in recent years due to a global interest in developing techniques for electrochemical energy conversion and storage, as well as elelectro-synthesis of valuable chemicals. The activity is one of the key performance parameters for electrocatalysts, while the observed activity can be affected by mass loading of electrocatalysts. Here, we take cobalt oxide (Co₃O₄)/graphite paper electrode (Co₃O₄/GPE) as a model electrode to demon-strate how the mass loading of Co₃O₄ catalyst influences ethylene glycol (EG) oxidation in alkaline (KOH) by cyclic votammetry (CV) and chronopentiometry (CP) approaches. Analyses from redox peaks and double layer capacitances reveal that increasing the mass loading provided more electrochemical active sites. Increasing loading made a positive contribution to EG oxidation at the low oxidation potential, while less significant improvement at the high oxidation potential. The results will provide some insight for optimzing the mass loading of electrocatalysts for electrocatalysis of small organic molecules.

Metal-ion batteries have changed our quotidian lives. The research on the electrode materials for metal-ion battery is the key to improve the performance of the battery. Therefore, understanding the structure-performance relationship of the electrode materials can help to improve the energy density and power density of the materials. Magnetic resonance, including nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR), has been continuously improved during the past three decades, and has gradually become one of the important technologies to study the structure-performance relationship of electrode materials. This paper summarizes the progress of magnetic resonance research from our group on several interesting electrode materials and demonstrates the important role of NMR and EPR in the study of electrode materials. This article will help to grasp the important value of magnetic resonance technology for battery research, which will promote the further development of advance magnetic resonance technology.

Nickel(Ni)-rich layered oxide has been regarded as one of the most important cathode materials for the lithium-ion batteries because of its low cost and high energy density. However, the concerns in safety and durability of this compound are still challenging for its further development. On this account, the in-depth understanding in the structural factors determining its capacity attenuation is essential. In this review, we summarize the recent advances on the degradation mechanisms of Ni-rich layered oxide cathode. Progresses in the structure evolution of Ni-rich oxide are carefully combed in terms of inner evolution, surface evolution, and the property under thermal condition, while the state-of-the-art modification strategies are also introduced. Finally, we provide our perspective on the future directions for investigating the degradation of Ni-rich oxide cathode.

Tin (Sn)-based materials have emerged as promising electrocatalysts for selective reduction of CO₂ to formate, but their overall performances are still limited by electrode structures which govern the accessibility to active sites, the electron transfer kinetics, and the catalytic stability. In this study, the heterostructured Sn/SnO₂ nanoparticles dispersed by N-doped carbon layer networks (Sn/SnO₂@NC) were synthesized by a melt-recrystallization method taking the low melting point of Sn (m.p. 232^oC). The N-doped carbon layer networks derived from polydopamine could attract more electrons on the electrocatalyst, serve as conductive agents and protect the ultrafine nanoparticles from agglomeration and dissolution. The Sn/SnO₂@NC electrode exhibited the greatly enhanced performance for CO₂ reduction to formate in CO₂-saturated 0.5 mol·L^-1 aqueous NaHCO₃ solution, showing a selectivity of 83% at only -0.9 V vs. RHE with a sustained current density of 17 mA·cm^-2 for extended periods. By coupling the catalytic electrode with a commercially available RuO₂ catalyst as the anode, the long-term CO₂/H₂O splitting has been achieved. Furthermore, a rechargeable aqueous Zn-CO₂ battery with Sn/SnO₂@NC as the cathode and Zn foil as the anode was constructed. It could output electric energy with an open circuit voltage of 1.35 V and a peak power density of 0.9 mW·cm^-2.

In electrochemistry, perhaps also in other time-honored scientific disciplines, knowledge labelled classical usually attracts less attention from beginners, especially those pressured or tempted to quickly jam into research fronts that are labelled, not always aptly, modern. In fact, it is a normal reaction to the burden of history and the stress of today. Against this context, accessible tutorials on classical knowledge are useful, should some realize that taking a step back could be the best way forward. This is the driving force of this article themed at physicochemical modelling of the electric (electrochemical) double layer (EDL). We begin the exposition with a rudimentary introduction to key concepts of the EDL, followed by a brief introduction to its history. We then elucidate how to model the EDL under equilibrium, using firstly the orthodox Gouy-Chapman-Stern model, then the symmetric Bikerman model, and finally the asymmetric Bikerman model. Afterwards, we exemplify how to derive a set of equations governing the EDL dynamics under nonequilibrium conditions using a unifying grand-potential approach. In the end, we expound on the definition and mathematical foundation of electrochemical impedance spectroscopy (EIS), and present a detailed derivation of an EIS model for a simple EDL. We try to avoid the omission of supposedly ‘trivial’ information in the derivation of models, hoping that it can ease the access to the wonderful garden of physical electrochemistry.

Water splitting is a promising technology to produce clean hydrogen if powered by renewable energies, where oxygen evolution is the rate determining step at an anode. Here we adjust the different crystal planes of the cobalt oxides catalyst to expose more effective active sites through a hydrothermal process, so as to improve the reaction activity for oxygen evolution. The samples were well characterized by TEM, SEM and XRD. Among the three synthetic crystal planes (100), (111) and (110) of spinel cobalt oxides, the (100) crystal plane has the highest intrinsic activity. Combining in-situ infrared and DFT calculations, we observed that the oxygen evolution reaction reached the lowest energy barrier on the (100) plane of the cobalt oxide crystal. Further XPS analysis showed that the highest Co³⁺/Co²⁺ ratio was observed on the surface of the nanocube samples, indicating that Co³⁺ is a more active site for oxygen evolution catalytic activity.

Oxygen reduction reaction (ORR) in alkaline electrolytes is an important electrochemical process for metal-air batteries and anion exchange membrane fuel cells (AEMFCs). However, the sluggish kinetics spurs intensive research on searching robust electrocatalysts. Non-precious metal catalysts (NPMCs) that can circumvent the cost and scarcity issues associated with platinum (Pt)-based materials have been pursued and the challenges lie in the performance improvement to rival Pt-based benchmarks. As the composition and structure of the NPMCs have a significant impact on the catalytic performance, precise regulation on the catalyst structure holds great promise to bridge the activity gap between NPMCs and Pt-based benchmarks. In this minireview, we aim to provide an overview of recent progress in the structural regulation on NPMCs towards improved performance. The four typical categories of NPMCs, i.e., metal-free carbon-based materials, metal compounds, metal encapsulated in graphitic layer and atomically dispersed metal-nitrogen-carbon materials, are firstly introduced, where catalytic active sites and catalytic mechanism are highlighted. Subsequently, we summarize the representative structural regulation from a nanoscale to an atomic scale including hierarchically porous structure regulation, interface engineering, defect engineering and atomic pair construction. Special emphasis is placed on the elucidation of the catalytic structure-performance relationship. The origins of activity improvements from these structural regulations are discussed in terms of accelerated mass transfer, increased accessible active sites, tailored electronic states, and synergetic effect between multi-components. Finally, the challenges and opportunities are discussed.

Theoretical simulations of electrocatalysis are vital for understanding the mechanism of the electrochemical process at the atomic level. It can help to reveal the in-situ structures of electrode surfaces and establish the microscopic mechanism of electrocatalysis, thereby solving the problems such as electrode oxidation and corrosion. However, there are still many problems in the theoretical electrochemical simulations, including the solvation effects, the electric double layer, and the structural transformation of electrodes. Here we review recent advances of theoretical methods in electrochemical modeling, in particular, the double reference approach, the periodic continuum solvation model based on the modified Poisson-Boltzmann equation (CM-MPB), and the stochastic surface walking method based on the machine learning potential energy surface (SSW-NN). The case studies of oxygen reduction reaction by using CM-MPB and SSW-NN are presented.