Bismuth oxyhalides and bismuth tungstate in photoelectrocatalysis: comprehensive insights on structural design, energy and environmental applications

Bismuth oxyhalides (BiOX; X = Cl, Br, I) and bismuth tungstate (Bi2WO6) are visible-light-responsive, chemically stable semiconductors with tunable electronic structures, making them promising photoelectrocatalysts for sustainable energy conversion and environmental remediation. This review integrates structural fundamentals, synthesis strategies, and heterojunction engineering (type-II, p-n, Z-scheme, and Schottky) to address limitations such as charge recombination and limited light absorption. Applications span water splitting, pollutant degradation, CO2 reduction, and nitrogen fixation, with quantitative performance comparisons and structure-property correlations. Current challenges and future research opportunities are highlighted to guide the rational design of BiOX- and Bi2WO6-based photoelectrocatalysts toward efficient, application-specific performance.