Best Practices in Using Foam-Type Electrodes for Electrocatalytic Performance Benchmark

Abstract

Best practices in using foam-type electrodes for electrocatalytic performance benchmark Open-pore foam-type electrodes are three-dimensional (3D) materials (typically, Ni, Cu, Fe, and C, images shown in Figure S1A) with a wide porosity range (70 ~ 98%) where their porous cellular structures are interconnected so fluid and gas can pass through. 1 The unique properties of conductive foams, such as high specific surface area and structural rigidity, make them suitable and popular supports on which the active materials are coated 2 or grown. [3][4]4][5] For example, nearly 8% of the water splitting electrocatalysts reported in 2019 (Figure S1B) involve foam-type electrodes, claiming outstanding electrocatalytic performances and superiority over the others (Figure S2).Electrocatalysts comparable to commercial noble metal catalysts are often found amid the headlines of various journals. 2,[5][6]Two indicators, overpotential at given current density (often 10 or 100 mA cm -2 , denoted as 10 or 100) and Tafel slope (potential required to achieve every current density increment of 10 mA cm -2 ), are usually employed for catalytic activity evaluation and comparison.However, we believe some oversimplified and overlooked quantitative and experimental issues in using foam-type electrodes have made the electrocatalyst benchmarking physically groundless and often incommensurable, eventually obstructing the understanding and rational design of electrocatalysts.In this Viewpoint, several problems of using foam-type electrodes as electrocatalyst support are discussed, proving some conventional approaches, such as current density normalization, surface area evaluation, and experimental setup, are problematic.(Figure 1) This is the Pre-Published Version.