Improving the onset potential and Tafel slope determination of earth-abundant water oxidation electrocatalysts

To date, a plethora of electrocatalysts for the Oxygen Evolution Reaction (OER) have been proposed. For evaluating their electrocatalytic behavior the determination of the onset potential in each studied electrolyte is a key parameter. Nevertheless, this evaluation becomes particularly problematic for first- transition metal catalysts as well as by the use of electroactive collectors ( e.g. Ni foams) whose redox peaks overlap the onset potential. A usual solution to detect the onset potential requires the availabil- ity of in-situ mass spectrometric determination of the generated oxygen. In this work, we present fast and easier available cyclic voltammetry and coulovoltammetric responses to determine the onset poten- tials of three benchmark electrocatalysts: a layered double hydroxide, a Prussian blue analogue and a β-Layered hydroxide. Cyclic coulovoltammetric responses allow, as we demonstrate here, a quantitative separation in the same potential range of the charge consumed by reversible (redox) reactions and the charge consumed by the irreversible reaction: the oxygen release. Quantifying the irreversible charges (that correspond to the OER) for different anodic potential limits permits the unambiguous determina- tion of both, the onset potential and the Tafel slope values without the catalyst redox contributions. As far as we know, this is the first time that this fast, available and cheap methodology has been applied for the OER determination. Thus, coulovoltammetry arises as a friendly and powerful tool for the investigation of electrocatalytic performances. To date, a plethora of electrocatalysts for the Oxygen Evolution Reaction (OER) have been proposed. For evaluating their electrocatalytic behavior the determination of the onset potential in each studied electrolyte is a key parameter. Nevertheless, this evaluation becomes particularly problematic for first- transition metal catalysts as well as by the use of electroactive collectors ( e.g. Ni foams) whose redox peaks overlap the onset potential. A usual solution to detect the onset potential requires the availabil- ity of in-situ mass spectrometric determination of the generated oxygen. In this work, we present fast and easier available cyclic voltammetry and coulovoltammetric responses to determine the onset poten- tials of three benchmark electrocatalysts: a layered double hydroxide, a Prussian blue analogue and a β-Layered hydroxide. Cyclic coulovoltammetric responses allow, as we demonstrate here, a quantitative separation in the same potential range of the charge consumed by reversible (redox) reactions and the charge consumed by the irreversible reaction: the oxygen release. Quantifying the irreversible charges (that correspond to the OER) for different anodic potential limits permits the unambiguous determina- tion of both, the onset potential and the Tafel slope values without the catalyst redox contributions. As far as we know, this is the first time that this fast, available and cheap methodology has been applied for the OER determination. Thus, coulovoltammetry arises as a friendly and powerful tool for the investigation of electrocatalytic performances.