Strategic Ni-doping improved electrocatalytic H2 production by Bi3O4Br in alkaline water†

Establishing a cost-effective and efficient electrocatalytic pathway for the hydrogen evolution reaction (HER) is the key to our quest for a carbon-neutral energy landscape. We report a simple and straightforward approach to synthesize an efficient, stable, and low-cost noble metal-free Bi₃O₄Br electrocatalyst. Tactical doping of Ni ions into Bi₃O₄Br effectively enhanced the conductivity, accelerated the charge transfer process, and provided more catalytic active sites to significantly boost the alkaline electrochemical HER performance of Bi₃O₄Br. This Ni-doped Bi₃O₄Br exhibited a lower overpotential of 662 mV compared to that of Bi₃O₄Br (736 mV) at a higher current density (50 mA cm⁻²). Additionally, the HER kinetics were also enhanced in terms of Tafel slope for this doped material (159 mV dec⁻¹) compared to the pristine Bi₃O₄Br (245 mV dec⁻¹), which coincides with a significant improvement in the mass activity (52 A g⁻¹ to 98 A g⁻¹). Notably, the overpotential of Ni-doped Bi₃O₄Br was further reduced to 614 mV at the same current density of 50 mA cm⁻² during photoelectrochemical HER performance testing, and the faradaic efficiency was improved from 79% to 87%. Finally, an enhanced durability of the material was observed for Bi₃O₄Br following the Ni-doping. Hence, this strategy highlights the importance of unravelling upgraded catalytic behaviour for abundant materials with rational doping.