Efficient regulation of surface hydroxyl groups on a Pt/Na/AC catalyst using two-step nonthermal plasma for high formaldehyde oxidation performance

Abstract

A novel catalyst was fabricated using a two-step nonthermal plasma method by regulating surface hydroxyl groups on Na/activated carbon (AC) with 0.1 wt% Pt loading (Pt/Na/AC (P&P)) and achieved high formaldehyde (HCHO) oxidation performance at ambient temperature. Based on characterization results, we found that in the first step of nonthermal plasma treatment under argon–water, the proportion of terminal OH groups (ter-OH groups) evidently increased. Following the introduction of Na and Pt, the relative abundance of doubly bridged OH groups connecting C and Na (bri_Na–C-OH groups) and Pt²⁺ species also increased in the second step of nonthermal plasma reduction under argon, resulting in enhanced HCHO catalytic oxidation capability through a rapid reaction pathway ([HCOO⁻] + [OH]_a → CO₂ + H₂O). Compared with the catalyst prepared via nitric acid oxidation and thermal deposition (Pt/Na/AC (H&T)), more Pt–O_x–Na species and surface OH groups were obtained on the Pt/Na/AC (P&P) catalyst, which not only reduced Pt consumption but also improved HCHO catalytic activity with around 100% conversion of HCHO to CO₂ at 25 °C, while the Pt/Na/AC (H&T) catalyst only achieved 70% conversion. This work thus provides a new strategy for HCHO oxidation at room temperature and a novel perspective on the environmentally friendly synthesis of effective noble catalysts.