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Guided by computational Pourbaix screening and high-throughput experiments aimed at the development of precious-metal-free fuel cells, we investigate rutile CoSb₂O₆ as an electrocatalyst for oxygen reduction in 1 M sulfuric acid. Following 4 h of catalyst conditioning at 0.7 V vs RHE, operation at this potential for 20 h yielded an average current density of −0.17 mA cm⁻² with corrosion at a rate of 0.04 nm hour⁻¹ that is stoichiometric with catalyst composition. Surface Pourbaix analysis of the (111) surface identified partial H coverage under operating conditions. The Sb active site has an HO* binding free energy of 0.49 eV, which is near the peak of the kinetic 4e⁻ ORR volcano for transition-metal oxides in acidic conditions. The experimental demonstration of operational stability and computational identification of a reaction pathway with favorable energetics place rutile CoSb₂O₆ among the most promising precious-metal-free electrocatalysts for oxygen reduction in acidic media.

The oxygen evolution reaction (OER) is central to several sustainable energy technologies. Catalyst development has largely focused on lowering the overpotential and eliminating reliance on precious metals, revealing stark differences in alkaline and acidic OER. In alkaline electrolyte, precious metal-free catalysts have approached the limiting overpotential from established free energy scaling relationships, and our survey of complex metal oxides shows that this limit can be approached with a broad range of catalysts. In acidic electrolyte, electrochemical instabilities create a dual challenge of a dearth of nonprecious metal OER catalysts with overpotential below 0.5 V and a high dissolved metals concentration for most precious metal-free catalysts. On device-relevant time scales, the high dissolved metals concentrations compromise device stability, for example, through a decrease of performance and due to metal exchange between anode and cathode catalysts due to finite permeability of ion exchange membranes. These considerations motivate a substantial increase in monitoring and reporting of dissolved metals concentrations in OER experiments. To facilitate durability-based screening in continued catalyst discovery campaigns, we introduce a durability descriptor based on the d-electron count of each metal element compared to that of its Pourbaix-stable oxidation state, which enables rapid down-selection of candidate metal oxide catalysts. We discuss the importance of a codesign approach to catalyst development, where a device architecture can set specific requirements for dissolved metals concentrations and/or cathode and anode catalysts can be designed to tolerate cross-contamination. This device-level guidance of basic science will facilitate deployment of new catalysts to meet the societal needs for accelerated sustainable technology development.

The hydrodynamics of electrochemical CO2 reduction (CO2R) systems is an insufficiently investigated area of research that has broad implications on catalyst activity and selectivity. While most previous reports are limited to laminar and CO2-sparged systems, herein we address a wide range of hydrodynamics via electrolyte recirculation systems. We find that increased hydrodynamics at the electrode surface results directly in changes to the ethylene and methane Tafel slopes, demonstrating that mass transport is on equal footing with catalyst active sites in determining reaction mechanisms and the ensuing product distribution. Mass transport is traditionally considered to be in the purview of systems-level engineering, yet the present work shows that CO2R mechanistic work must be considered in the context of the mass transport conditions. We extend our analysis to organic coatings, demonstrating that the films shield the active sites from variability in hydrodynamics and increase the residence time of CO so that it may be further reduced to desirable products.

Boundary conditions for catalyst performance in the conversion of common precursors such as N2, O2, H2O, and CO2 are governed by linear free energy and scaling relationships. Knowledge of these limits offers an impetus for designing strategies to alter reaction mechanisms to improve performance. Typically, experimental demonstrations of linear trends and deviations from them are composed of a small number of data points constrained by inherent experimental limitations. Herein, high-throughput experimentation on 14 bulk copper bimetallic alloys allowed for data-driven identification of a scaling relationship between the partial current densities of methane and C2+ products. This strict dependence represents an intrinsic limit to the Faradaic efficiency for C–C coupling. We have furthermore demonstrated that coating the electrodes with a molecular film breaks the scaling relationship to promote C2+ product formation., High-throughput experimentation on the reduction of CO2 on copper alloys led to the identification of a scaling relationship between CH4 and C2+ products that can be broken with an organic additive.