Pulsed‐UV illumination on graphene oxide: A new strategy in photocatalytic synthesis of electrocatalysts to control the structural and electrochemical properties

Abstract

Summary This study demonstrated the capability of a novel method in controlling the structural and electrochemical properties of electrocatalysts, utilizing a pulsed‐ultraviolet (UV) setup for the synthesis procedure. A hand‐made reactor provided a new set of parameters. The variation of UVon and UVoff periods resulted in samples with a range of different structures, compositions, and activities. Graphene/Pt was prepared with varying forms of illumination pulse, and its hydrogen oxidation and oxygen reduction reaction performances were evaluated. Controlling the reduction degree of Pt ions on partially reduced graphene oxide was achieved by manipulating the setup design. The results revealed a dominant growth and agglomeration phase of Pt particles, mostly with metallic states, by increasing both UVon and Uoff time spontaneously. Long UVon without adequate UVoff did not result in promising electrocatalytic activities. In other words, different structures, compositions, and activities of samples suggested that not just the illumination is the crucial factor, it is also the resting time or UVoff which determines the surface adsorption kinetics, nucleation sites, and growth mechanism of nanoparticles. Further chemical reduction by highly concentrated ascorbic acid was used to confirm the proposed mechanisms, which lead to samples even with more metallic Pt (Pt0).

Co2+, Fe2+, and Ni2+: Modifiers for Photocatalytic Deposition of Highly Active Pt on Graphene-Based Supports

“…Based on a study conducted by Wang et al, metal ions, M + , could be attracted to negatively charged GO sheets and cause partial neutralization of GO (eq ). false[ GO false] − x + x normalM + → GOM x However, methanol (as an organic hole scavenger) and water molecules tend to form hydrogen bonds with GO functional groups. The probability of forming a hydrogen bond between water molecules and GO is much more than forming the bond between the methanol molecule and GO, especially when the GO has already been stored in aqueous solutions …”

“…To assess the number of active sites for the hydrogen oxidation reaction, HOR, CV experiments were conducted (Figure ). Results from previous investigations have shown that the current approach produces Pt ions with a very high deposition efficiency and stability. ,, Based on those results, the ECSA and ORR performance were calculated with respect to 20 wt % Pt loading. The most promising electrochemical activity was for the sample prepared with a high concentration of Co 2+ , with the ECSA value of 191 m 2 ·g –1 .…”

“…The mass activities of the other two samples were 0.39 A·mg –1 and 0.25 A·mg –1 for the ones prepared by Fe 2+ and Ni 2+ , respectively. In different studies in which the synthesis and/or support materials were different types of carbon materials, mass activities were reported to be in the range of 0.063–0.272 A·mg –1 . ,, The summary of the electrochemical performances is presented in Table .…”

“…Based on a study conducted by Wang et al, metal ions, M + , could be attracted to negatively charged GO sheets and cause partial neutralization of GO (eq ). However, methanol (as an organic hole scavenger) and water molecules tend to form hydrogen bonds with GO functional groups. The probability of forming a hydrogen bond between water molecules and GO is much more than forming the bond between the methanol molecule and GO, especially when the GO has already been stored in aqueous solutions …”

“…In different studies in which the synthesis and/or support materials were different types of carbon materials, mass activities were reported to be in the range of 0.063−0.272 A•mg −1 . 2,52,62 The summary of the electrochemical performances is presented in Table 2.…”