Traditional understanding of electrocatalytic reactions generally focuses on either covalent interactions between adsorbates and the reaction interface (i.e., electrical double layer, EDL) or electrostatic interactions between electrolyte ions. Here, our work provides valuable insights into interfacial structure and ionic interactions during alkaline oxygen evolution reaction (OER). The importance of inner-sphere OH − adsorption is demonstrated as the IrO x activity in 4.0 M KOH is 6.5 times higher than that in 0.1 M KOH. Adding NaNO 3 as a supporting electrolyte, which is found to be inert for long-term stability, complicates the electrocatalytic reaction in a half cell. The nonspecially adsorbed Na + in the outer compact interfacial layer is suggested to form a stronger noncovalent interaction with OH − through hydrogen bond than adsorbed K + , leading to the decrease of interfacial OH − mobility. This hypothesis highlights the importance of outer-sphere adsorption for the OER, which is generally recognized as a pure inner-sphere process. Meanwhile, based on our experimental observations, the pseudocapacitive behavior of solid-state redox might be more reliable in quantifying active sites for OER than that measured from the conventional EDL charging capacitive process. The interfacial oxygen transport is observed to improve with increasing electrolyte conductivity, ascribing to the increased accessible active sites. The durability results in a liquid alkaline electrolyzer which shows that adding NaNO 3 into KOH solution leads to additional degradation of OER activity and long-term stability. These findings provide an improved understanding of the mechanistic details and structural motifs required for efficient and robust electrocatalysis.

A composite silica–divinylbenzene (SiO2/DVB) adsorbent was prepared for the adsorption of ethanol from the ethanol–water mixture. Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and a Brunauer, Emmett and Teller surface area analyzer were utilized for the characterization analysis of the adsorbents. Batch experiments were executed at different initial ethanol concentrations (10–95 vol %), contact times (1–24 h), and temperatures (10–40 °C). The equilibrium studies indicated a favorable adsorption of ethanol on SiO2/DVB because of a separation factor R l of 0.18 from the Langmuir model. Moreover, Freundlich parameter constant n was found to be 2.37. This implies that the adsorption is governed by a physical process. Results in the experimental data best-fitted the pseudo-second-order kinetic model (R 2 ≥ 0.98 and RMSE ≤ 1.26), which suggests chemisorption as the rate-limiting step of the adsorption system. Based on the Weber–Morris kinetic analysis, intraparticle diffusion occurred after the outer surface of the SiO2/DVB became saturated by ethanol molecules. Approximately 99.2 ± 0.4% (20 °C) and 99.8 ± 0.2% (30 °C) of the ethanol were adsorbed onto the SiO2/DVB adsorbent. Furthermore, thermodynamic parameters indicated a nonspontaneous and exothermic reaction in the adsorption process. It was revealed that the reusability profile of SiO2/DVB showed a 5.3% reduction in terms of the adsorption capacity after the first cycle and 8.3% reduction after four cycles.

There is an emerging interest in developing bifunctional oxygen electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), being key electrochemical reactions that govern the overall performance of unitized regenerative fuel cells and rechargeable metal-air batteries. However, such undertaking has been a huge challenge due to the high cost of noble metals (e.g. Pt, Ir) and their stability when used as catalysts. Herein, we report CoMn2O4 embedded on three-dimensional (3D) hierarchical porous carbon (HPC) derived from waste corn cobs as a possible noble metal-free bifunctional electrocatalyst. The hybrid catalyst is fabricated by solvothermal reaction of as-prepared N-doped 3DHPC and CoMn2O4. The template-free approach in preparing N-3DHPC ensures ample nitrogen doping using melamine to improve electronic conductivity of carbon and formation of threedimensional, interconnected pore network, which is favorable for CoMn2O4 crystal dispersion. The same hybrid material also presents good OER activity, rendering an active and inexpensive dual-function electrocatalyst.

With the continued depletion of conventional fuel sources, the search for alternative fuel becomes increasingly important. Low temperature fuel cells such as PEMFCs and AFCs have attracted significant attention as a power generation technology. However, the cost of noble metals—which are important in speeding up the sluggish oxygen reduction reaction—remains an impediment in the commercialization of this technology. Metal-free catalysts are now being seen as possible alternatives to these noble metals. Among these metal-free catalysts is the graphitic carbon nitride. Graphitic carbon nitride, g-C3N4, is a polymeric material consisting of C, N, and some impurity H, connected via tris-triazine-based patterns. Due to its unique electronic structure, g-C3N4 and other graphene analogs have garnered interest in the material science community. While previous studies have been able to show experimentally the activity of g-C3N4 towards ORR, ab initio studies to explain and generalize the findings of the experiments remain scarce. Here we explain from the standpoint of density functional theory (DFT) calculations the effect of heteroatom doping (e.g., phosphorus, boron, sulfur) in further altering the material’s electronic structure in an effort to render g-C3N4 more active towards oxygen reduction reaction. The trends exhibited by graphitic carbon nitrides in our DFT computations indicate that this emerging class of material can pave the way for the rational design of fuel cell catalysts.