Mitigating Challenges of the Neutral Oxygen Evolution Reaction: The Undervalued Importance of Electrolyte Engineering

Water splitting in quasi-neutral electrolytes (5 ≤ pH ≤ 10) offers advantages over highly alkaline or acidic electrolytes by improving operational safety, simplifying maintenance, and enabling the use of diverse natural water sources. Such electrolytes suggest promise for large-scale applications, especially considering their widened catalyst scope. However, kinetically restrained oxygen evolution reaction (OER) catalysts exhibit decreased electrochemical performance in these conditions, marked by reduced activity and increased overpotential. This problem has been primarily addressed by exploring catalyst design without proper consideration of the electrolyte; its role is often undervalued and overlooked. Electrolyte parameters, including ionic species, pH, physicochemical properties, etc., profoundly impact the OER. If not properly chosen, catalyst surface interactions, local pH swings, and factors like mass transport can become nonideal. Therefore, quasi-neutral electrolytes must be methodically selected for a given system. In this perspective, we present the challenges faced in quasi-neutral electrolytes and emphasize points of consideration for quasi-neutral OER electrolytes by systematically reviewing the literature. First, we explore buffers and local pH, and the surface interactions between the catalyst and the electrolyte. Next, we discuss electrolyte additives and their promise to enhance the OER by altering the electric double layer and hydrogen bonding environment. Lastly, we address the critical role of mass transport through the lens of physicochemical properties and external parameters. Overall, a strategic approach, encompassing an informed choice of an electrolyte and modification of its properties, is suggested for enhancing OER performance to drive quasi-neutral electrochemical water splitting innovations.