Electrocatalytic 2e⁻ oxygen reduction reaction (2e⁻ ORR) is a promising approach to producing H₂O₂ at ambient temperature and pressure especially in acidic media, which, however, is hindered by the high cost of precious metal-based electrocatalysts. Hence, the development of efficient earth-abundant electrocatalysts and reaction mechanism exploration for H₂O₂ production by 2e⁻ ORR in acidic solution are critically important but remain challenging at present. In this work, NiSe₂ has been developed as a novel and high-performance 2e⁻ ORR electrocatalyst in acidic media, moreover, using nickel chalcogenides as the models, the influence of different anion species (Se₂²⁻, S₂²⁻, and O²⁻) on 2e⁻ ORR electrocatalytic performance of the catalysts has been investigated. The synthesized NiSe₂ exhibits outstanding 2e⁻ ORR performance of high selectivity (90%) and long-term durability (12 h). The maximum H₂O₂ concentration of NiSe₂ reaches 988 ppm, which is the highest among all the reported transition metal chalcogenides. This work demonstrates a novel point of view in anion tuning for designing high-efficiency transition-metal-based electrocatalysts for 2e⁻ ORR.

Developing anode catalysts of substantially enhanced activity for hydrogen oxidation reaction (HOR) and anti-CO poisoning performance is of great importance for the application of proton exchange membrane fuel cells (PEMFCs). Herein, we report Pd cluster in situ decorated urchin-like W₁₈O₄₉ (WO_2.72) electrocatalysts by a photo-reduction method for high performance HOR. The synthesized Pd-WO_2.72-L composite of low loading amount of 0.44 wt.% Pd by Xenon light reduction exhibits markedly high HOR catalytic activity and stability in 0.5 M H₂SO₄, and the specific HOR current density and mass activity of Pd-WO_2.72-L are ~ 1.5 and ~ 80 times those of 20 wt.% Pt/C catalyst, respectively. Moreover, excellent anti-CO poisoning ability has also been obtained. The excellent HOR activity and anti-CO poisoning performance of Pd-WO_2.72-L have been discussed mainly in terms of the dual synergetic catalytic effects between Pd and WO_2.72: Pd activation to Pd^δ+ by the electron transfer from Pd to W promotes the hydrogen adsorption and activation to H* species, which results in largely elevated HOR activity; Pd degradation due to the CO poisoning is effectively prevented by WO_2.72, which is responsible for the excellent CO-tolerance performance.