Influence of sputtering power on oxygen reduction reaction activity of zirconium oxides prepared by radio frequency reactive sputtering

Effects of a conductive support on the bonding of oxygen containing molecules to transition metal oxide surfaces

Conventional oxygen electrocatalysts are expensive for industrial use. Transition metal oxides (TMOs), as a more economical option, have emerged as an alternative to potentially replace conventional precious metal catalysts. However, many experimental studies have suggested that although a few of the TMOs supported by conductive substrates are stable under electrocatalytic conditions, their performances are far from the industrial level, especially in the acidic oxygen reduction reaction (ORR). At present, their ORR and also oxygen evolution reaction (OER) performances are still not well understood. In this study, we analyze the effects of the support on ORR/OER adsorbate binding to TMO catalysts. We show that for wide bandgap TMOs (e.g., ZrO2 and HfO2), the use of a metal support leads to a marked enhancement of the adsorbate binding strengths due to a significant induced electron charge gain in the adsorbates, and a considerable up-shift in the ORR/OER adsorbate binding scaling relation. Meanwhile, these support-induced effects are significant even with relatively thick TMO layers on a thin metal substrate, requiring a large thickness cutoff to eliminate the influence. In contrast, the metal-like TMOs (e.g., PdO2 and SnO2) are less affected by the metal support. This study suggests that the thickness of the TMO layer can be used to tune the adsorption properties of electronegative adsorbates and thus provides an interesting new design option for oxygen electrocatalysis.

A Pt-free graphenaceous composite as an electro-catalyst for efficient oxygen reduction reaction

Use of Pt-based electro-catalysts for the oxygen reduction reaction (ORR) is a major hindrance in large-scale application of proton exchange membrane fuel cells (PEMFCs). Hence, new, cost-effective and high performance electro-catalysts are required for the commercial success of PEMFCs. In this work, a Pt-free magnesium oxide (MgO) decorated multi-layered reduced graphene oxide (MLGO) composite is tested as an electro-catalyst for the ORR. The ORR activity of MgO/MLGO in terms of diffusion-controlled current density is found to be superior (6.63 mA per cm2-geo) than that of in-house prepared Pt/rGO (5.96 mA per cm2-geo) and commercial Pt/C (5.02 mA per cm2-geo). The applicability of less expensive MgO/MLGO not only provides a new electro-catalyst but also provides a new direction in exploring metal oxide-based electro-catalysts for the ORR.

An adamantane-based COF: stability, adsorption capability, and behaviour as a catalyst and support for Pd and Au for the hydrogenation of nitrostyrene

A bimodal (micro/mesoporous) COF was synthesized by coupling tetrakis-1,3,5,7-(4′-iodophenyl)adamantane with 4,4′-diethynylbiphenyl following a Sonogashira protocol.

Novel VN/C nanocomposites as methanol-tolerant oxygen reduction electrocatalyst in alkaline electrolyte

A novel VN/C nanostructure consisting of VN nanoparticles and graphite-dominant carbon layers is synthesized by nitridation of V₂O₅ using melamine as reductant under inert atmosphere. High crystalline VN nanoparticles are observed to be uniformly distributed in carbon layers with an average size of ca13.45 nm. Moreover, the electrocatalytic performance of VN/C towards oxygen reduction reaction (ORR) in alkaline electrolyte is fascinating. The results show that VN/C has a considerable ORR activity, including a 75 percent value of the diffusion-limited current density and a 0.11 V smaller value about the onset potential with respect to Pt/C catalyst. Moreover, the excellent methanol-tolerance performance of VN/C has also been verified with 3 M methanol. Combined with the competitive prices, this VN/C nanocomposite can serve as an appropriate non-precious methanol-tolerant ORR catalyst for alkaline fuel cells.