New paradigms in electrocatalysis with alternative oxidation reactions

Abstract Electrochemical systems are rapidly evolving beyond traditional water electrolysis, including cathodic hydrogen evolution (HER) and anodic oxygen evolution (OER) reactions, to enhance energy efficiency and generate value-added products simultaneously. Cathodic reactions now facilitate multifunctional reductions – ranging from CO 2 conversion into oxygenates and hydrocarbons to nitrogen (N 2 ) fixation, and nitrate (NO 3 − ) reduction – by tuning operational parameters. Hybrid co-reduction approaches, such as CO 2 /nitrile or CO 2 /nitrate, further enable the synthesis of valuable amines, amides and urea derivatives, among many others. Notably, even in the most advanced electrochemical configurations, the inclusion of the OER – or a functionally equivalent alternative – remains the most convenient oxidation reaction for maintaining charge balance within the cell. As highlighted in recent studies, alternative oxidation reactions (AORs) coupled with cathodic reduction reactions, such as CO 2 RR, HER, N 2 RR and NO 3 RR, are essential for overcoming the limitations of OER. These AORs include oxidation of biomass-derived alcohols and aldehydes, chlorine and water contaminants. In this perspective, we discuss the emerging promise of AORs – with a particular focus on aldehyde electrooxidation – as innovative alternatives to traditional OER. This strategy not only reduces the energy requirements for electrochemical hydrogen production by circumventing the sluggish and energy-intensive OER, but also enables concurrent hydrogen generation at both electrodes. Additionally, integrating AORs into electrolyzer design enables the direct coupling of CO 2 reduction at the cathode with high-value chemical transformations at the anode, offering new opportunities for process intensification and enhanced economic viability in the synthesis of sustainable fuels and chemicals.