Unveiling the microstructure and promising electrochemical performance of heavily phosphorus-doped diamond electrodes

• Published in: Electrochimica acta 2024-09, Vol.499, p.144696, Article 144696
• Main Authors: Baluchová, Simona, Sung, Kil-dong, Weiss, Zdeněk, Kopeček, Jaromír, Fekete, Ladislav, Buijnsters, Josephus G., Mortet, Vincent
• Format: Article
• Language: English
• Subjects: Cyclic voltammetry analysis; Electrochemical characterisation; Gas flow control; n-Type conductivity; Phosphorus-doped diamond (PDD)
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2024.144696

•Heavily doped PDD electrodes pioneered for novel electrochemical applications.•Phosphorus doping manipulated via phosphine gas concentration and gas flow control.•Increasing p content leads to a gradual decrease in the diamond grain size.•Enhanced p incorporation boosts electrochemical performance of PDD electrodes.•Well-developed voltammetric signals obtained on PDD electrodes for the first time. The challenge of doping synthetic diamond with phosphorus stems from the atomic size mismatch between phosphorus and carbon atoms, which previously hindered achieving high phosphorus doping levels. This limitation delayed the exploration of phosphorus-doped diamond (PDD) in electrochemical applications, where it holds potential as a novel and appealing electrode material because PDD uniquely combines diamond's exceptional properties with phosphorus atoms inducing n-type conductivity. In this study, heavily doped PDD electrodes were successfully developed using chemical vapour deposition, followed by comprehensive microstructural and electrochemical characterisations. The influence of phosphorus doping, manipulated via high phosphine gas concentration or time-dependant precursor gas flow control, on the PDD properties was thoroughly examined. PDD layers grown at higher phosphine concentrations demonstrated enhanced phosphorus incorporation, leading to a higher prevalence of fine nano-crystalline diamond grains and non-diamond carbon components, while also slowing the growth rate. Notably, a distinct PDD sample produced under dynamic gas flow with lower phosphine concentration revealed larger grain sizes, increased effective deposition rate, and improved phosphorus levels compared to its counterpart synthesized under static conditions. Cyclic voltammetry in a 1 mol L−1 KCl solution revealed a low double-layer capacitance (