An integrated amorphous cobalt phosphoselenide electrocatalyst with high mass activity boosts alkaline overall water splitting

Developing integrated non-noble metal electrocatalysts with mass activity comparable to noble metal is a significant challenge for overall water splitting. Herein, we constructed an integrated amorphous cobalt phosphoselenide (a-CoPSe) electrode via amorphization and dual anion-mediated strategy, achieving a significant improvement in the electrochemical active surface area (ECSA) and turnover frequency (TOF). The a-CoPSe offers large ECSA (65.9 m2 g-1) and high TOF values of 35.7 s-1 for hydrogen evolution reaction (HER) and 31.9 s-1 for oxygen evolution reaction (OER) at 300 mV. The mass activities of a-CoPSe are 890.4 A g-1Co for HER at 300 mV and 677.4 A g-1Co for OER at 250 mV, which are comparable to commercial Pt/C (10014.6 A g-1) and RuO2 (232.6 A g-1). Theoretical calculation reveals amorphous cobalt with balanced charges regulated by phosphorus and selenium atoms simultaneously facilitate H2O*, H*, OH* and OOH* adsorption, which greatly promotes the HER and OER kinetics.