Recent progress in the development of efficient biomass-based ORR electrocatalysts

Platinum is considered the reference catalyst in many electrochemical devices such as electrolyzers or fuel cells. Nevertheless, the large-scale commercialization of these Pt-based devices is limited by the prohibitive cost of platinum as well as its quantity and availability. Regardless of its price and scarcity, it is well known that the oxygen reduction reaction (ORR) with Pt in acidic media is slow compared to that in alkaline media. Due to the lower overpotentials in the latter case, the possibility of using Pt-free catalysts opens the door to new catalyst research. Among them, the development of carbon-based catalysts, either metal-free or with non-precious metals, from the conversion of biomass precursors by various synthetic processes has recently become a challenging goal, as biomass represents an eco-friendly source of carbon. The surface chemistry, textural properties and structure of carbonaceous materials make it complex to identify the origin of ORR catalytic activities. This review provides a critical discussion of the influence of the physicochemical and electrochemical properties of biomass-derived, carbon-based electrocatalysts for the ORR reported over the past decade.