Additionally, while the Cu2O photoanode showed a slight decreased photocurrent density in water oxidation during 15 h (Supplementary Fig. ), it demonstrated excellent stability over 40 h in sulfite oxidation, with only negligible efficiency loss (Fig. ). We assume that this is due to the absence of gas bubble formation during sulfite oxidation, which prevents the detachment of the front layers, thereby improving the durability of the Cu2O photoanode . In this regard, we anticipate that strategies aimed at enhancing gas bubble formation and detachment through surface treatments or focusing on alternative reactions such as biomass or ammonia oxidation could facilitate the development of more efficient and especially durable PEC devices using p-type Cu2O photoanodes. Given that the Cu2O photoanode already exhibits superior PEC performance in water oxidation compared to other n-type metal oxides, further research holds significant potential for advancing this PEC system (Fig. ).