Pd‐Modified De‐alloyed Au−Ni‐Microelectrodes for In Situ and Operando Mapping of Hydrogen Evolution

Abstract

To date most studies focusing on light‐driven water splitting for green energy conversion schemes depend on bulk analyses of the produced hydrogen using, e. g., head‐space gas chromatography. In this contribution, we present the fabrication of Pd‐modified microelectrodes for in situ electrochemical hydrogen measurements using de‐alloyed Au−Ni microelectrodes. Stability studies and pH‐dependent investigations revealed the stability of these microsensors over a period of seven days, and confirmed their applicability in a pH range of 3–10 with a limit of detection (LOD)<1 μmol/L. First in situ proof‐of‐principle electrochemical imaging of hydrogen generated at a microelectrode and operando studies of hydrogen evolution at earth‐abundant cobalt hydrogen evolution catalysts using the developed Pd‐microsensors in combination with scanning electrochemical microscopy (SECM) demonstrated the potential of these microsensors for operando studies in light‐driven heterogeneous catalysis.

Operando Scanning Electrochemical Probe Microscopy during Electrocatalysis

“…492 Kund and co-workers fabricated a Pd-modified dealloyed Au−Ni microelectrode tip, which they used for the detection of H 2 under operando conditions at a Pt UME substrate during HER. 493 In this study, the tip potential was kept constant (2 V vs Ag/AgCl quasi-RE) to oxidize H 2 (HOR) while cycling the substrate potential (0.1 V to −1.2 V vs Ag/AgCl quasi-RE). Figure 6c,d is a schematic of a Pd-modified microelectrode positioned above the spot where H 2 is evolved and over an insulating surface as control measurement.…”

“…(d) Schematic of a Pd-modified microelectrode positioned over the insulating sheath, i – t curve H 2 absorption at the Pd-modified microelectrode (red) and cyclic voltammogram recorded at the Pt macroelectrode (gray). Reproduced with permission from ref ( 493 ). Copyright 2022 John Wiley & Sons, Ltd. (e) Schematic illustration of the FB, RC, and SG-TC detection modes.…”

“…The capability of the proposed probe for the quantification of H 2 at heterogenized Co-based HER catalysts under illumination was demonstrated. 493 Visibile et al proposed the use of a cavity microelectrode modified with the studied materials in the TG-SC mode as a simple and fast method for screening different semiconductor materials (core–shell CuI/CuO 2 to estimate their efficiencies toward H 2 (or O 2 ) production under photocorrosion conditions. 494 When a photocathodic material was used, the potential of the Pt substrate was held constant at the value for hydrogen oxidation, while when a photoanodic powder was under study at the value for oxygen reduction.…”

“…Kund and co-workers fabricated a Pd-modified dealloyed Au–Ni microelectrode tip, which they used for the detection of H 2 under operando conditions at a Pt UME substrate during HER . In this study, the tip potential was kept constant (2 V vs Ag/AgCl quasi-RE) to oxidize H 2 (HOR) while cycling the substrate potential (0.1 V to −1.2 V vs Ag/AgCl quasi-RE).…”

“…Figure c,d is a schematic of a Pd-modified microelectrode positioned above the spot where H 2 is evolved and over an insulating surface as control measurement. The capability of the proposed probe for the quantification of H 2 at heterogenized Co-based HER catalysts under illumination was demonstrated . Visibile et al proposed the use of a cavity microelectrode modified with the studied materials in the TG-SC mode as a simple and fast method for screening different semiconductor materials (core–shell CuI/CuO 2 to estimate their efficiencies toward H 2 (or O 2 ) production under photocorrosion conditions .…”